{"id":35586,"date":"2023-10-18T16:00:15","date_gmt":"2023-10-18T21:00:15","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=35586"},"modified":"2025-08-18T15:33:45","modified_gmt":"2025-08-18T20:33:45","slug":"cyclopropanation-of-alkenes","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2023\/10\/18\/cyclopropanation-of-alkenes\/","title":{"rendered":"Cyclopropanation of Alkenes"},"content":{"rendered":"<p><strong>Cyclopropanation of Alkenes<\/strong><\/p>\n<p>Alkenes can undergo\u00a0<strong>addition\u00a0<\/strong>reactions from <strong>carbenes <\/strong>to give <strong>cyclopropanes<\/strong>. There are three main pathways for this reaction that are generally covered in introductory organic chemistry.<\/p>\n<ul>\n<li>The simplest method is treatment of diazomethane (CH<sub>2<\/sub>N<sub>2<\/sub>) with light (&#8220;photolysis&#8221;) to give methylene carbene, which adds to alkenes to form cyclopropanes. This reaction has the downside of being very difficult to control and also uses toxic and explosive diazomethane.<\/li>\n<li>A robust method which still sees considerable use today is the use of diiodomethane (CH<sub>2<\/sub>I<sub>2<\/sub>) with zinc-copper couple (a 90:10 alloy of zinc and copper) which forms cyclopropanes with alkenes via a metal &#8220;carbenoid&#8221; species.<\/li>\n<li>Haloforms (e.g. CHCl<sub>3<\/sub>, CHBr<sub>3<\/sub>) when treated with strong base (e.g. KOH or KO<em>t<\/em>-Bu) will undergo deprotonation followed by loss of a leaving group to give\u00a0<strong>dihalocarbenes<\/strong>. These can also undergo addition to alkenes.<\/li>\n<li>Cyclopropanation proceeds through a concerted transition state and is <strong>stereospecific.\u00a0<\/strong><\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-35711\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/0-summary-of-cyclopropanation-reactions-for-alkenes-diazomethane-simmons-smith-and-halocyclopropanation.gif\" alt=\"summary of cyclopropanation reactions for alkenes - diazomethane simmons smith and halocyclopropanation\" width=\"640\" height=\"453\" \/><\/a><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li style=\"list-style-type: none;\">\n<ol>\n<li><a href=\"#one\">Cyclopropanation of Alkenes<\/a><\/li>\n<li><a href=\"#two\">Cyclopropanation is Stereospecific<\/a><\/li>\n<li><a href=\"#three\">The Cyclopropanation Mechanism &#8211; Photolysis of CH2N2<\/a><\/li>\n<li><a href=\"#four\">The Simmons-Smith Mechanism<\/a><\/li>\n<li><a href=\"#five\">Dihalocyclopropanation of Alkenes<\/a><\/li>\n<li><a href=\"#six\">The Dihalocyclopropanation Mechanism<\/a><\/li>\n<li><a href=\"#seven\">Reactions of Cyclopropanes<\/a><\/li>\n<li><a href=\"#eight\">Summary<\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quiz\">Quiz Yourself!<\/a><\/li>\n<li><a href=\"#references\">(Advanced) References and Further Reading<\/a><\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<hr \/>\n<h2><a id=\"one\"><\/a>1. Cyclopropanation of Alkenes<\/h2>\n<p>Cyclopropanes are the smallest cycloalkane rings. Due to the fact that their internal angles (60\u00b0) are considerably smaller than the ideal tetrahedral bond angle (109.5\u00b0), they have considerable (<em>27 kcal\/mol<\/em>)<strong> angle strain<\/strong>. \u00a0(<span style=\"color: #993366;\"><em>see article: <\/em><\/span><a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/04\/03\/cycloalkanes-ring-strain-in-cyclopropane-and-cyclobutane\/\"><span style=\"color: #993366;\"><em>Ring Strain in Cyclopropane and Cyclobutane<\/em><\/span>)<\/a>.<\/p>\n<p><span style=\"color: #000000;\"> If you&#8217;ve ever tried to make a cyclopropane with a molecular model kit, you will quickly discover that the little pieces of plastic will not forgive you for trying to bend them into a constrained triangular shape.<\/span><\/p>\n<p>Given this, it might come as a surprise that these unhappy little cycloalkanes can be readily made via addition reactions to alkenes. But they can!<\/p>\n<p>For example, one of the oldest methods for formation of cyclopropanes involves irradiating diazomethane (CH<sub>2<\/sub>N<sub>2<\/sub>) with visible light (<em>hv<\/em>) in the presence of an alkene.<\/p>\n<p>In this reaction, two new C-C bonds are formed, a C-C pi bond is broken, and a C-N bond breaks, liberating nitrogen gas (N<sub>2<\/sub>).<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-35655\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/1-summary-for-cyclopropanation-of-alkenes-using-diazomethane-irradiated-with-light.gif\" alt=\"summary for cyclopropanation of alkenes using diazomethane irradiated with light\" width=\"640\" height=\"308\" \/><\/a><\/p>\n<p><span style=\"color: #993366;\"><em>A lot of other side reactions happen too, which we need not get into at the moment. [<a href=\"#noteone\"><span style=\"color: #ff0000;\">Note 1<\/span><\/a> ] Let&#8217;s just say that for best results, this reaction is best run using the alkene as the <strong>solvent<\/strong> to minimize the many other side reactions that can happen here.<\/em><\/span><\/p>\n<p>A key observation that has been made about this process is that cyclopropanation occurs such that the <strong>stereochemistry<\/strong> about the alkene is conserved. [<a href=\"#reffive\"><em>See Ref<\/em><\/a>]<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-35656\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/2-examples-of-cyclopropanation-of-alkenes-with-diazomethane-and-light-to-give-methylene-carbene.gif\" alt=\"examples of cyclopropanation of alkenes with diazomethane and light to give methylene carbene\" width=\"640\" height=\"459\" \/><\/a><\/p>\n<p>Diazomethane is the source of many laboratory horror stories and requires special safety precautions for use in the lab. (<span style=\"color: #993366;\"><em>See article &#8211; <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2011\/11\/05\/reagent-friday-diazomethane-ch2n2\/\">Diazomethane<\/a><\/em><\/span>). It is highly explosive. Dintrogen (N<sub>2<\/sub>), an excellent leaving group, is only held on to carbon by a thread,\u00a0 and careless jostling, heat, strong light, or even the <em>rough surface of ground-glass joints<\/em> can be enough to cause detonation.<\/p>\n<p>And, oh, by the way, it is also highly toxic.<\/p>\n<p>Therefore, it must have been something of a relief in 1958 when two researchers from DuPont in Wilmington, Delaware published a robust method for cyclopropane formation that avoided diazomethane altogether.<\/p>\n<p>Simmons and Smith found that treating diiodomethane (CH<sub>2<\/sub>I<sub>2<\/sub>) with zinc-copper couple (<span style=\"color: #993366;\"><em>a 90:10 alloy of finely divided zinc and copper<\/em><\/span>) results in a highly reactive intermediate that smoothly forms cyclopropanes from alkenes.<\/p>\n<p>This reaction, which has come to be known as the <strong>Simmons-Smith cyclopropanation<\/strong>, works well with a broad variety of alkenes.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35657\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/3-the-simmons-smith-reaction-uses-zinc-copper-couple-and-diiodomethane-to-give-cyclopropanes-from-alkenes.gif\" alt=\"the simmons smith reaction uses zinc copper couple and diiodomethane to give cyclopropanes from alkenes\" width=\"640\" height=\"367\" \/><\/a><\/p>\n<h2><a id=\"two\"><\/a>2. Cyclopropanation is Stereospecific<\/h2>\n<p>Cyclopropanation of alkenes always results in\u00a0<em>syn\u00a0<\/em>addition of the CH<sub>2<\/sub> to the alkene.<\/p>\n<p>If you try making the model of the anti addition product you will see why. It&#8217;s similar to why double bonds can only be <em>cis<\/em> in small rings; a\u00a0<em>trans<\/em> arrangement results in too much ring strain.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35658\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/4-cis-and-trans-cyclopropanes-and-why-trans-cyclopropanes-are-too-strained-to-exist.gif\" alt=\"cis and trans cyclopropanes and why trans cyclopropanes are too strained to exist\" width=\"640\" height=\"221\" \/><\/a><\/p>\n<p>Furthermore, cyclopropanation is an example of a <strong>stereospecific <\/strong>reaction. The stereochemistry about the double bond is always conserved. Two groups that are\u00a0<em>cis<\/em> to each other on the alkene will be\u00a0<em>cis<\/em> to each other on the cyclopropane ring.<\/p>\n<p>For example, the two alkenes, <em>cis<\/em>&#8211; and\u00a0<em>trans<\/em>&#8211; hex-3-ene, are <strong>stereoisomers<\/strong> that differ only in the configuration at a single carbon.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35659\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/5-cyclopropanation-is-stereospeicific-none-of-the-other-stereoisomers-are-observed-example-with-cis-and-trans-3-hexene.gif\" alt=\"cyclopropanation is stereospeicific - none of the other stereoisomers are observed - example with cis and trans 3 hexene\" width=\"640\" height=\"575\" \/><\/a><\/p>\n<ul>\n<li>Cyclopropanation of\u00a0<em>cis<\/em>-hex-3-ene results in a single product, (<em>3S,4R<\/em>)-diethylcyclopropane (a meso compound).<\/li>\n<li>Cyclopropanation of\u00a0<em>trans<\/em>-hex-3-ene results in a <strong>racemic mixture<\/strong> of two products, (<em>3S, 4S<\/em>)-diethylcyclopropane and (<em>3R, 4R<\/em>)-diethylcyclopropane.<\/li>\n<\/ul>\n<p>The products of these reactions are\u00a0<strong>stereoisomers\u00a0<\/strong>of each other, which fulfills <a href=\"https:\/\/goldbook.iupac.org\/terms\/view\/S05994\">IUPAC&#8217;s<\/a> definition of a stereospecific process. (<span style=\"color: #993366;\"><em>Other examples of stereospecific reactions are halogenation of alkenes, dihydroxylation of alkenes, and epoxidation of alkenes &#8211; See article &#8211;<a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/07\/02\/stereoselective-stereospecific\/\"> Stereoselective and Stereospecific Reactions<\/a>).\u00a0<\/em><\/span><\/p>\n<p>See if you can draw the product of the reaction below and predict the relationship between the products.<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"35668\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"35668\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"35668\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"35668\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-35668\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-35668 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"35668\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-xmvvg\" data-id=\"xmvvg\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2605-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2605-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>Here&#8217;s another one:<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"35669\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"35669\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"35669\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"35669\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-35669\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-35669 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"35669\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-tys67\" data-id=\"tys67\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2606-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2606-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>See if you can\u00a0<strong>work backwards\u00a0<\/strong>from the product below to give the starting alkene.<\/p>\n<!-- quiz #35586 not found -->\n<h2><a id=\"three\"><\/a>3. The Cyclopropanation Mechanism &#8211; Photolysis of CH<sub>2<\/sub>N<sub>2<\/sub><\/h2>\n<p>Now that we&#8217;ve seen a few examples of cyclopropanation, the next logical question is to ask <strong>how it works.<\/strong><\/p>\n<p>In introductory courses it&#8217;s somewhat rare to go into much detail on this. <span style=\"color: #993366;\"><em>One reason is that the cyclopropane products don&#8217;t really participate in many reactions we subsequently cover in this course,\u00a0 so given the inevitable time constraints, their mechanisms get glossed over.<\/em><\/span><\/p>\n<p>We&#8217;ll cover it briefly because it provides a fun excursion into the world of carbenes.<\/p>\n<p>When diazomethane is treated with light, the C-N bond breaks to liberate nitrogen gas (N<sub>2<\/sub>). (<span style=\"color: #993366;\"><em>This is called, &#8220;photolysis&#8221;, literally, &#8220;breaking with light&#8221;<\/em><\/span>).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35660\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/9-formation-of-methylene-carbene-from-photolysis-of-diazomethane-giving-ch2-singlet-carbene.gif\" alt=\"-formation of methylene carbene from photolysis of diazomethane giving ch2 singlet carbene\" width=\"640\" height=\"351\" \/><\/a><\/p>\n<p>So what&#8217;s left behind?<\/p>\n<p>If you follow the curved arrow, you&#8217;ll be led to the conclusion that the species left behind is simply a CH<sub>2<\/sub> group with a lone pair on it. This is\u00a0known as <strong>methylene carbene. Carbenes<\/strong>, like carbocations and free radicals, are highly reactive, electron-deficient reaction intermediates.<\/p>\n<p>Since we&#8217;re here, why not take a quick quiz. What would you expect to be the 1) formal charge\u00a0 and 2) the hybridization of the central carbon in methylene carbene?<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"35671\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"35671\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"35671\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"35671\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-35671\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-35671 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"35671\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-7f2fo\" data-id=\"7f2fo\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2608-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2608-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>Methylene carbene is a <strong>neutral<\/strong>, six-electron species. It is <em>extremely reactive<\/em> and pretty much impossible to control. Of all the wild horses in our stable of organic chemistry reagents, I can&#8217;t think of a wilder one than methylene carbene.<\/p>\n<p>For best results, the alkene should be used as solvent. Even solvents we consider relatively inert, like pentane and benzene, will undergo reaction with methylene carbene.\u00a0 (<span style=\"color: #ff0000;\"><em style=\"color: #ff0000;\"><span style=\"color: #993366;\">For some of methylene carbene&#8217;s greatest hits, see this<\/span> <a href=\"#noteone\">Note 1<\/a>)<\/em><\/span><\/p>\n<p>As we saw earlier, the cyclopropanation of alkenes is <strong>stereospecific<\/strong>. This is a clue that the reaction proceeds through a\u00a0<strong>concerted<\/strong> mechanism.<\/p>\n<p><span style=\"color: #993366;\"><em>(Reactions that <strong>aren&#8217;t<\/strong> stereospecific, such as addition of H-X to alkenes, and free-radical addition of H-Br to alkenes, tend to proceed through carbocation or free-radical intermediates that can undergo bond rotation.)<\/em><\/span><\/p>\n<p>The mechanism for the reaction can be drawn as the concerted addition of methylene carbene to the C-C pi bond as in the drawing below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41661\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/11-reaction-of-methylene-carbene-with-alkenes-to-give-a-new-cyclopropane-transition-state-mechanism.gif\" alt=\"reaction of methylene carbene with alkenes to give a new cyclopropane transition state mechanism\" width=\"640\" height=\"357\" \/><\/a><\/p>\n<p>For the purposes of arrow pushing, you can think of the carbene as possessing both nucleophilic and electrophilic character; the lone pair on carbon forms one of the C-C bonds, whereas the empty orbital on the carbene carbon accepts a pair of electrons from the alkene pi bond.<\/p>\n<p><span style=\"color: #993366;\"><em>There is actually another way to distribute the electrons in methylene carbene that would result in a stepwise mechanism. See <a href=\"#notetwo\"><span style=\"color: #ff0000;\">Note 2<\/span><\/a>]<\/em><\/span><\/p>\n<h2><a id=\"four\"><\/a>4. The Simmons-Smith Cyclopropanation Mechanism<\/h2>\n<p>Cyclopropanation through the Simmons-Smith method, CH<sub>2<\/sub>I<sub>2<\/sub>\/Zn(Cu), also passes through a concerted transition state.<\/p>\n<p><span style=\"color: #993366;\"><em>Again, if you&#8217;re taking an introductory course, this mechanism is rarely tested, so think of this as a fun bonus excursion.\u00a0<\/em><\/span><\/p>\n<p>It might be helpful to think of the reaction between CH<sub>2<\/sub>I<sub>2<\/sub> and zinc-copper couple as a fancy version of the Grignard reaction (<span style=\"color: #993366;\"><em>See article &#8211; <span style=\"color: #993366;\"><a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2015\/11\/09\/synthesis-of-grignard-and-organolithium-reagents\/\">Formation of Grignard and Organolithium Reagents<\/a><\/span><\/em><\/span>).\u00a0 The carbon-halogen bond breaks, and the metal atom (zinc in this case) <strong>inserts<\/strong> itself between the carbon and the halogen.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35662\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/12-formation-of-carbenoid-in-the-simmons-smith-cyclopropanation-reaction-mechanism-with-zinc-copper-couple.gif\" alt=\"formation of carbenoid in the simmons smith cyclopropanation reaction mechanism with zinc copper couple\" width=\"640\" height=\"247\" \/><\/a><\/p>\n<p>Since carbon is much more electronegative (2.5) than zinc (1.65), the carbon bonded to zinc will have significant negative charge and behave much like a <strong>carbanion<\/strong>. And since the carbon is also bonded to iodine, a <strong>good leaving group,<\/strong> it&#8217;s not too far off to imagine an equilibrium where I-Zn-CH<sub>2<\/sub>-I loses I-Zn(+) and I(-) , giving methylene carbene.<\/p>\n<p>For that reason these types of species are known as <strong>carbenoids<\/strong>.\u00a0 <span style=\"color: #000000;\">To see an image of this &#8220;equilibrium&#8221; <\/span>, <a href=\"\" class=\"custom-tooltip\" data-image=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/Supp-1-why-is-the-product-of-reaction-of-zinc-coper-couple-with-diiodomethane-called-a-carbenoid.gif\" data-link=\"\" data-title=\"\" data-text=\"\">hover here<\/a> or click this <a href=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/Supp-1-why-is-the-product-of-reaction-of-zinc-coper-couple-with-diiodomethane-called-a-carbenoid.gif\">link<\/a>.<\/p>\n<p>Think of them as kinder, gentler versions of methylene carbene. They don&#8217;t react with solvents like diethyl ether, for instance.<\/p>\n<p>The proposed concerted mechanism for the Simmons Smith cyclopropanation is similar to that for methylene carbene, except it incorporates loss of the carbon-zinc and the carbon-iodine bonds. [<a href=\"#refsix\">Ref<\/a>]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35663\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/13-mechanism-for-cyclopropanation-in-the-simmons-smith-reaction-concerted-addition-to-alkenes.gif\" alt=\"mechanism for cyclopropanation in the simmons smith reaction concerted addition to alkenes\" width=\"640\" height=\"386\" \/><\/a><\/p>\n<p><span style=\"color: #993366;\"><em>Note that the Simmons-Smith cyclopropanation only really works for CH<sub>2<\/sub>I<sub>2<\/sub> . An attempt to use diiodoethane (CH<sub>3<\/sub>CHI<sub>2<\/sub>) for cyclopropanation gave a very low yield (4%).\u00a0\u00a0<\/em><\/span>[<a href=\"#notethree\"><span style=\"color: #ff0000;\">Note 3<\/span><\/a>]<\/p>\n<h2><a id=\"five\"><\/a>5. Dihalocyclopropanation of Alkenes<\/h2>\n<p>Another kinder, gentler procedure for the cyclopropanation of alkenes involves the treatment of <strong>haloforms<\/strong> (e.g. CHCl<sub>3<\/sub>, CHBr<sub>3<\/sub>, CHI<sub>3<\/sub>) with strong base.<\/p>\n<p>For example, when an alkene is treated with bromoform (CHBr<sub>3<\/sub>) in the presence of the strong base potassium t-butoxide, the\u00a0<strong>dihalocyclopropane\u00a0<\/strong> is formed.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35664\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/14-halocyclopropanation-to-alkenes-using-haloforms-and-strong-base-with-alkenes-gives-dihalocyclopropanes.gif\" alt=\"halocyclopropanation to alkenes using haloforms and strong base with alkenes gives dihalocyclopropanes\" width=\"640\" height=\"262\" \/><\/a><\/p>\n<p>The reaction works well with chloroform and bromoform. (<span style=\"color: #993366;\"><em>It presumably would work well with iodoform too, but C-I bonds are very sensitive to light.)<\/em><\/span><\/p>\n<p>Like the cyclopropanation reactions we&#8217;ve seen previously, the reaction is also stereospecific.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35665\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/15-dihalocyclopropanation-is-a-concerted-addition-to-an-alkene-stereospecific-some-examples.gif\" alt=\"dihalocyclopropanation is a concerted addition to an alkene - stereospecific-some examples\" width=\"640\" height=\"323\" \/><\/a><\/p>\n<p>See if you can predict the products:<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"35672\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"35672\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"35672\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"35672\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-35672\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-35672 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"35672\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-lth5k\" data-id=\"lth5k\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2609-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2609-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>Another example:<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"35673\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"35673\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"35673\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"35673\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-35673\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-35673 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"35673\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-xesuc\" data-id=\"xesuc\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2610-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2610-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<h2><a id=\"six\"><\/a>6. Dihalocyclopropanation &#8211; The Mechanism<\/h2>\n<p>So what&#8217;s going on here? Since no reaction happens in the absence of base, we should expect that the first step is deprotonation of whatever species is the <strong>strongest acid<\/strong> in solution. That would be the\u00a0<strong>haloform<\/strong>.<\/p>\n<p>Although bases like hydroxide and t-butoxide don&#8217;t normally deprotonate C-H bonds, the presence of three electronegative C-halogen bonds helps to make the C-H bond of CHCl<sub>3<\/sub> and CHBr<sub>3<\/sub><strong>\u00a0<\/strong>considerably more acidic than a normal C-H bond. <em><span style=\"color: #993366;\">The estimated pK<sub>a<\/sub> of chloroform is about 15.7, very similar to that of alcohols and water. [<a style=\"color: #993366;\" href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja00772a008\">Ref<\/a>]<\/span><\/em><\/p>\n<p>Once the haloform is deprotonated to give a carbanion, it can subsequently undergo loss of a leaving group to give the neutral\u00a0<strong>dihalocarbene<\/strong>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35666\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/18-mechanism-for-the-alpha-elimination-of-haloforms-to-give-dihalocarbenes-via-deprotonation-of-haloform.gif\" alt=\"mechanism for the alpha elimination of haloforms to give dihalocarbenes via deprotonation of haloform\" width=\"640\" height=\"567\" \/><\/a><\/p>\n<p>This overall process &#8211; breakage of C-H and loss of a leaving group on the same carbon &#8211; is known as\u00a0<strong>alpha-elimination,\u00a0<\/strong>as distinguished from <strong>beta-elimination\u00a0<\/strong>where the leaving group departs from the carbon\u00a0<strong>adjacent<\/strong> to the carbon being deprotonated <span style=\"color: #993366;\"><em>(e.g. in the E1 and E2 mechanisms).\u00a0<\/em><\/span><\/p>\n<p>Once the dihalocarbene is formed, the next step is cyclopropanation of the alkene, which proceeds similarly to what we&#8217;ve seen earlier:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35667\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/19-mechanism-for-the-dihalocyclopropanation-of-alkenes-with-dihalocarbenes.gif\" alt=\"mechanism for the dihalocyclopropanation of alkenes with dihalocarbenes\" width=\"640\" height=\"265\" \/><\/a><\/p>\n<h2><a id=\"seven\"><\/a>7. Reactions of Cyclopropanes (?)<\/h2>\n<p>Having considerable ring strain (27 kcal\/mol) cyclopropanes are somewhat spring-loaded towards reactions that will result in opening the ring. They are similar to epoxides in this regard (<span style=\"color: #993366;\"><em>See article: <a href=\"https:\/\/www.masterorganicchemistry.com\/2015\/02\/10\/opening-of-epoxide-with-base\/\">Ring Opening of Epoxides<\/a><\/em><\/span>).<\/p>\n<p>However, unlike epoxides\u00a0there aren&#8217;t really any\u00a0<strong>general<\/strong> reactions of cyclopropanes that are typically covered in introductory organic chemistry. The main reason is that the leaving group is carbon instead of oxygen, and carbanions are much stronger bases than alkoxides and therefore worse leaving groups. Opening a cyclopropane with a nucleophile is difficult unless you have a good electron withdrawing group attached to it that can delocalize the charge.<\/p>\n<p>So for the purposes of introductory organic chemistry, cyclopropane formation is one of those reactions that is presented in the chapter on alkenes but doesn&#8217;t really get developed further at a later part in the course. For that reason it&#8217;s often the first reaction to be dropped when instructors are short on time.<\/p>\n<h2><a id=\"eight\"><\/a>8. Summary<\/h2>\n<p>Alkenes combine with carbenes (and carbenoids) to give cyclopropanes. We saw a variety of ways of making carbenes.<\/p>\n<p>Cyclopropanation of alkenes is similar to dihydroxylation, epoxidation, and hydrogenation of alkenes in that<\/p>\n<ul>\n<li>The reaction proceeds through a concerted transition state<\/li>\n<li>The reaction gives the products of\u00a0<em>syn<\/em> addition<\/li>\n<li>The reaction is stereospecific<\/li>\n<\/ul>\n<p>For studying purposes, I generally suggest grouping these reactions together with hydroboration to give a family of reactions some may reasonably call &#8220;The Concerted Pathway&#8221; (<span style=\"color: #993366;\"><em>See article: <a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/02\/epoxidation-hydroxylation-cyclopropanation-alkene-mechanism\/\">Alkene Addition Pattern #3, The &#8220;Concerted Pathway<\/a><\/em><\/span>&#8220;).<\/p>\n<hr \/>\n<h2><strong><a id=\"notes\"><\/a>Notes<\/strong><\/h2>\n<div class=\"related-articles\"><p><strong>Related Articles<\/strong><\/p><ul><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/06\/17\/reagent-friday-m-cpba-meta-chloroperoxybenzoic-acid\/\" class=\"\"><span>m-CPBA (meta-chloroperoxybenzoic acid)<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/02\/epoxidation-hydroxylation-cyclopropanation-alkene-mechanism\/\" class=\"\"><span>Alkene Addition Pattern #3: The \u201cConcerted\u201d Pathway<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/07\/01\/reagent-friday-oso4-osmium-tetroxide\/\" class=\"\"><span>OsO4 (Osmium Tetroxide) for Dihydroxylation of Alkenes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/04\/03\/cycloalkanes-ring-strain-in-cyclopropane-and-cyclobutane\/\" class=\"\"><span>Cycloalkanes \u2013 Ring Strain In Cyclopropane And Cyclobutane<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/05\/23\/whats-a-racemic-mixture\/\" class=\"\"><span>What\u2019s a Racemic Mixture?<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2018\/09\/10\/types-of-isomers\/\" class=\"\"><span>Types of Isomers: Constitutional Isomers, Stereoisomers, Enantiomers, and Diastereomers<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/03\/28\/hydroboration-of-alkenes-the-mechanism\/\" class=\"\"><span>Hydroboration Oxidation of Alkenes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/03\/15\/alkene-bromination-mechanism\/\" class=\"\"><span>Halogenation of Alkenes and Halohydrin Formation<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/11\/05\/reagent-friday-diazomethane-ch2n2\/\" class=\"\"><span>Diazomethane (CH2N2)<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2015\/11\/09\/synthesis-of-grignard-and-organolithium-reagents\/\" class=\"\"><span>Formation of Grignard and Organolithium Reagents<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/11\/25\/hydrogenation-alkenes-palladium-on-carbon-pdc\/\" class=\"\"><span>Palladium on Carbon (Pd\/C) for Catalytic Hydrogenation of Alkenes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/07\/02\/stereoselective-stereospecific\/\" class=\"\"><span>Stereoselective and Stereospecific Reactions<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/01\/22\/alkene-addition-regioselectivity-syn-anti\/\" class=\"\"><span>Alkene Addition Reactions: \u201cRegioselectivity\u201d and \u201cStereoselectivity\u201d (Syn\/Anti)<\/span><\/a><\/li><\/ul><\/div>\n<p><strong><a id=\"noteone\"><\/a>Note 1<\/strong>. Methylene carbene will do things that few other reactive intermediates will do, such as participating in reactions with relatively inert compounds like benzene and alkanes. The problem is that it is impossible to control.<\/p>\n<p>For example, it will make cyclopropanes from benzene.<\/p>\n<p>The other amazing reaction methylene carbene will do is to <strong>insert<\/strong> itself into C-H bonds, resulting in the lengthening of alkanes (and alkenes) by a single CH<sub>2<\/sub> unit.<\/p>\n<p>Two of the side products in this cyclopropanation study were cis-2-pentene and 2-methyl-2-butene.<\/p>\n<p>Methylene will react with ordinary alkanes as well. In heptane, it gives a mixture of <em>n<\/em>-octane and octane isomers. The reaction is not very selective, however.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F1-greatest-hits-of-methylene-carbene-cyclopropanation-of-benzene-and-C-H-insertion-reactions.gif\" alt=\"greatest hits of methylene carbene - cyclopropanation of benzene and C-H insertion reactions\" width=\"640\" height=\"674\" \/><\/a><\/p>\n<p><strong><a id=\"notetwo\"><\/a>Note 2<\/strong>. There is actually another way to draw the electron configuration of a carbene.<br \/>\n<div class=\"wq-quiz-wrapper\" data-id=\"35721\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"35721\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"35721\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"35721\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-35721\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-35721 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"35721\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-g0kkv\" data-id=\"g0kkv\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2621-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2621-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper --><\/p>\n<p>One of the important conclusions of the 1959 Snell study [<a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01522a058\">Ref<\/a>] was that the stereospecificity of the reaction showed that the reaction essentially went through a singlet carbene. Had cyclopropanation gone through addition of a triplet carbene, there would be an intermediate carbon radical capable of undergoing bond rotation, which would have led to a mixture of stereoisomers.<\/p>\n<p><strong><a id=\"notethree\"><\/a>Note 3<\/strong>. Scope of the Simmons Smith cyclopropanation process\u00a0 [<a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01525a036\">Ref<\/a>] (<span style=\"color: #993366;\"><em>from 1959 &#8211; many modifications have been made since then!<\/em><\/span>)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35715\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F3-Substrate-Table-for-Simmons-Smith-J-Am-Chem-Soc-1959.png\" alt=\"Substrate Table for Simmons Smith J Am Chem Soc 1959\" width=\"640\" height=\"888\" srcset=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F3-Substrate-Table-for-Simmons-Smith-J-Am-Chem-Soc-1959.png 865w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F3-Substrate-Table-for-Simmons-Smith-J-Am-Chem-Soc-1959-216x300.png 216w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F3-Substrate-Table-for-Simmons-Smith-J-Am-Chem-Soc-1959-738x1024.png 738w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F3-Substrate-Table-for-Simmons-Smith-J-Am-Chem-Soc-1959-768x1065.png 768w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F3-Substrate-Table-for-Simmons-Smith-J-Am-Chem-Soc-1959-548x760.png 548w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><\/a><\/p>\n<p>Generally, the more electron rich the alkene, the more reactive it is with the Simmons-Smith reagent, although steric hindrance can play a role.<\/p>\n<p><span style=\"color: #993366;\"><em>(This is from <a style=\"color: #993366;\" href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01061a017\">JACS 1964, 1347<\/a>)\u00a0<\/em><\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35716\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons.png\" alt=\"Relative Reactivity Table JACS 1963 Simmons\" width=\"640\" height=\"301\" srcset=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons.png 1954w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons-300x141.png 300w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons-1024x482.png 1024w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons-768x362.png 768w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons-1536x723.png 1536w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F4-Relative-Reactivity-Table-JACS-1963-Simmons-760x358.png 760w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><\/a><\/p>\n<p><strong><a id=\"notefour\"><\/a>Note 4.\u00a0<\/strong>Cyclopropanation of alkynes is also possible. This naturally occurring cyclopropene was formed from the cyclopropanation of an alkyne, a mere 2 years after the original Simmons-Smith report <span style=\"color: #993366;\"><em>(albeit in 4% yield)\u00a0<\/em><\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35717\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F5-Synthesis-of-sterculic-acid-via-cyclopropanation-of-an-alkyne-J-Am-Chem-Soc-1960.gif\" alt=\"Synthesis of sterculic acid via cyclopropanation of an alkyne J Am Chem Soc 1960\" width=\"640\" height=\"220\" \/><\/a><\/p>\n<p><strong><a id=\"notefive\"><\/a>Note 5.\u00a0<\/strong>Many natural products contain cyclopropanes. The current record is 6, contained in this molecule known as U-106305, isolated in 1990 from fermentation of a\u00a0<em>Streptomyces\u00a0<\/em>variant.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-35718\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/10\/F6-Strange-natural-product-with-six-cyclopropanes-named-U-106305.gif\" alt=\"-Strange natural product with six cyclopropanes named U-106305\" width=\"640\" height=\"160\" \/><\/a><\/p>\n<p>It has been synthesized (<a href=\"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/ja9619420\">Ref<\/a>) by the research group of Prof. Andre Charette (U. Montreal)\u00a0 through application of successive Simmons-Smith cyclopropanation reactions. Charette&#8217;s research group has made many advances in the synthesis of enantiomerically enriched cyclopropanes.<\/p>\n<hr \/>\n<h2><strong><a id=\"quiz\"><\/a>Quiz Yourself!<\/strong><\/h2>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3279-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3280-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/1638-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/1639-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/1640-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2607-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n<hr \/>\n<h2><strong><a id=\"references\"><\/a>(Advanced) References and Further Reading<\/strong><\/h2>\n<p>Simmons-Smith Reaction:<\/p>\n<ol>\n<li><strong>A New Synthesis of Cyclopropanes<\/strong><br \/>\nHoward E. Simmons and Ronald D. Smith<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1959<\/strong> 81 (16), 4256-4264<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01525a036\">10.1021\/ja01525a036<\/a><br \/>\nThis full paper, expanded from the original report (JACS 1958 5323) explains the development of the reaction and provides a lot of experimental detail on its scope (broad), its stereospecificity, and proposes a mechanism.<\/li>\n<li><strong>Cyclopropanes from Unsaturated Compounds, Methylene Iodide, and Zinc-Copper Couple<\/strong><br \/>\nSimmons, H. E.; Cairns, T. L.; Vladuchick, S. A.; Hoiness, S. A. <em>Org. Reactions<\/em> <strong>1973, <\/strong>20, 1-133<br \/>\n<strong>DOI:<\/strong> <a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/0471264180.or020.01\">10.1002\/0471264180.or020.01<\/a><br \/>\nThis chapter in <em>Organic Reactions<\/em> has everything you need to know about the Simmons-Smith reaction, including mechanistic studies, experimental procedures, and substrate scope.<\/li>\n<li><strong>NORCARANE<br \/>\n<\/strong> D. Smith and H. E. Simmons<br \/>\n<em>Org. Synth.<\/em> <strong>1961<\/strong>, <em>41<\/em>, 72<br \/>\n<strong>DOI<\/strong>: <a href=\"http:\/\/www.orgsyn.org\/demo.aspx?prep=CV5P0855\">10.15227\/orgsyn.041.0072<\/a><br \/>\nA detailed procedure for the Simmons-Smith reaction in <em>Organic Syntheses<\/em>, including the preparation of the Zn-Cu couple.<\/li>\n<li><strong>The Addition of Dichlorocarbene to Olefins<\/strong><br \/>\nWilliam von E. Doering and A. Kentaro Hoffmann<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1954<\/strong> <em>76<\/em> (23), 6162-6165<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01652a087\">10.1021\/ja01652a087<\/a><br \/>\nThe original paper describing the synthesis of dichlorocyclopropanes from alkenes with chloroform and KOtBu, by William von Eggers Doering.<\/li>\n<li><strong>1,6-Methano[10]Annulene<br \/>\n<\/strong>E. Vogel, W. Klug, and A. Bruer<br \/>\n<em>Org. Synth.<\/em> <strong>1974<\/strong> <em>54<\/em>, 11<br \/>\n<strong>DOI: <\/strong><a href=\"http:\/\/www.orgsyn.org\/demo.aspx?prep=CV6P0731\">10.15227\/orgsyn.054.0011<\/a><br \/>\nThe second step in this procedure is the synthesis of a dichlorocyclopropane, by addition of dichlorocarbene to an alkene.<\/li>\n<li><strong><a id=\"reffive\"><\/a>Methylene, CH2. Stereospecific Reaction with cis- and trans-2-Butene<\/strong><br \/>\nRobert C. Woodworth and Philip S. Skell<br \/>\nJournal of the American Chemical Society <strong>1959<\/strong> 81 (13), 3383-3386<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01522a058\">10.1021\/ja01522a058<\/a><br \/>\nIn this study the authors find that photolysis of diazomethane in the presence of\u00a0<em>cis<\/em>&#8211; and\u00a0<em>trans<\/em>&#8211; 2-butene results in stereospecific cyclopropanation, indicating that it goes through a single carbene intermediate.<\/li>\n<li><strong><a id=\"refsix\"><\/a>A DFT Study of the Simmons\u2212Smith Cyclopropanation Reaction<\/strong><br \/>\nFernando Bernardi, Andrea Bottoni, and Gian Pietro Miscione<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1997<\/strong> 119 (50), 12300-12305<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja971995x\">10.1021\/ja971995x<\/a><br \/>\nCalculations of the transition state for cyclopropanation of alkenes.<\/li>\n<li><strong>Stereoselective Cyclopropanation Reactions<\/strong><br \/>\nH\u00e9l\u00e8ne Lebel, Jean-Fran\u00e7ois Marcoux, Carmela Molinaro, and Andr\u00e9 B. Charette<br \/>\n<em>Chemical Reviews<\/em> <strong>2003<\/strong> 103 (4), 977-1050<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/cr010007e\">10.1021\/cr010007e<\/a><br \/>\nSince the development of the Simmons-Smith reaction a tremendous amount of work has gone into developing enantioselective variants. This review is quite comprehensive.<\/li>\n<li><strong>SYNTHESIS OF STERCULIC ACID<\/strong>\n<div>Nicholas T. Castellucci and Claibourne E. Griffin<\/div>\n<div><cite>Journal of the American Chemical Society<\/cite>\u00a0<strong>1960<\/strong>\u00a0<em>82<\/em> (15), 4107-4107<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01500a070\">10.1021\/ja01500a070<\/a><br \/>\nSynthesis of a naturally occurring cyclopropene through cyclopropanation of an alkyne.<\/div>\n<\/li>\n<li><strong>Cyclopropane Synthesis from Methylene Iodide, Zinc-Copper Couple, and Olefins. III. The Methylene-Transfer Reaction<br \/>\n<\/strong>Howard E. Simmons, Elwood P. Blanchard, and Ronald D. Smith<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1964<\/strong> 86 (7), 1347-1356<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01061a017\">10.1021\/ja01061a017<\/a><br \/>\nFurther study on the Simmons-Smith reaction, studying the mechanism and properties of the active reagent.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Cyclopropanation of Alkenes Alkenes can undergo\u00a0addition\u00a0reactions from carbenes to give cyclopropanes. There are three main pathways for this reaction that are generally covered in introductory <\/p>\n","protected":false},"author":1,"featured_media":35711,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1418],"tags":[14866,169,14867,14868,639,971,296,14869,910,14870],"post_folder":[],"class_list":["post-35586","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-alkene-reactions","tag-addition-reaction","tag-alkenes","tag-carbene","tag-carbenoid","tag-cycloaddition","tag-cyclopropane","tag-diazomethane","tag-halocyclopropane","tag-simmons-smith","tag-zncu"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Cyclopropanation of Alkenes &#8211; Master Organic Chemistry<\/title>\n<meta name=\"description\" content=\"Cyclopropanation of alkenes can be performed with CH2N2 and light (hv), CH2I2 and Zn(Cu) or from haloforms (e.g. CHBr3) with base. 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