{"id":13174,"date":"2014-12-14T08:07:50","date_gmt":"2014-12-14T08:07:50","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=13174"},"modified":"2014-12-14T08:48:06","modified_gmt":"2014-12-14T08:48:06","slug":"cyclopropanation-the-mechanism-of-the-simmons-smith-reaction","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13174","title":{"rendered":"Cyclopropanation: the mechanism of the Simmons\u2013Smith reaction."},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"13174\">\n<p>These posts contain the computed potential energy surfaces for a fair few &#8220;text-book&#8221; reactions. Here I chart the course of the cyclopropanation of alkenes using the Simmons-Smith reagent,<span id=\"cite_ITEM-13174-0\" name=\"citation\"><a href=\"#ITEM-13174-0\">[1]<\/a><\/span> as\u00a0prepared from di-iodomethane using zinc metal insertion into a C-I bond.<br \/>\n<a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/simmonds-smith.svg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-13175\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/simmonds-smith.svg\" alt=\"simmonds-smith\" width=\"300\" \/><\/a><\/p>\n<p>Two reactions it can be compared with are the <a title=\"Experimental evidence for \u201chidden intermediates\u201d? Epoxidation of ethene by peracid.\" href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=11065\" target=\"_blank\">epoxidation of ethene <\/a>using a peracid and <a title=\"The direct approach is not always the best: ethene + dichlorocarbene\" href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=6977\" target=\"_blank\">dichlorocyclopropanation<\/a>. The latter is a four-electron pericyclic process, which is thermally forbidden. The outcome there is that the two new bonds form very asynchronously to <a title=\"(anti)aromaticity avoided: a tutorial example\" href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=2973\" target=\"_blank\">avoid transition state antiaromaticity<\/a>. The former is a more complex reaction, best described as a six-electron process\u00a0which allows both C&#8230;O bonds to form at the same rate. So which of these two does the\u00a0Simmons\u2013Smith mechanism correspond to?<\/p>\n<p>The calculation as undertaken at a \u03c9B97XD\/Def2-TZVPD-PP (solvent=dichloromethane) level<span id=\"cite_ITEM-13174-1\" name=\"citation\"><a href=\"#ITEM-13174-1\">[2]<\/a><\/span> shows the two C&#8230;C bonds forming at more or less the same rate. The reaction therefore resembles epoxidation rather than dichlorocyclopropanation.<\/p>\n<p><a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS.jpg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-13182\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS.jpg\" alt=\"SS\" width=\"300\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS.jpg 432w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-289x300.jpg 289w\" sizes=\"(max-width: 432px) 100vw, 432px\" \/><\/a><\/p>\n<p>The\u00a0intrinsic reaction coordinate (IRC)<span id=\"cite_ITEM-13174-2\" name=\"citation\"><a href=\"#ITEM-13174-2\">[3]<\/a><\/span> is shown below, revealing a concerted and almost synchronous reaction. The synchronicity is all the more surprising given the diversity of bonds forming\/breaking.<br \/>\n<a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SSa1.gif\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-13189\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SSa1.gif\" alt=\"SSa\" width=\"400\" \/><\/a><br \/>\n<a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SSE1.svg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-13190\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SSE1.svg\" alt=\"SSE\" width=\"400\" \/><\/a><\/p>\n<p><a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SSG1.svg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-13191\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SSG1.svg\" alt=\"SSG\" width=\"400\" \/><\/a><\/p>\n<p>There are slight and tantalizing hints that the alkene and the I-Zn-CH<sub>2<\/sub>-I components initially form a weak \u03c0-complex, which then rearranges into the TS, and then again a weak complex at the end. The NCI surfaces for both are shown below, and show clear signs of dispersion-like stabilisations for both of them!\u00a0The strange torus around the Zn-I bond is due to the need for a lower density threshold to filter out the covalent interactions.<\/p>\n<div id=\"attachment_13196\" style=\"width: 290px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-13196\" class=\"size-full wp-image-13196\" onclick=\"jmolInitialize('..\/Jmol\/');jmolSetAppletColor('white');jmolApplet([450,450],'load wp-content\/uploads\/2014\/12\/SS-react_den.cub.xyz;isosurface colour red blue wp-content\/uploads\/2014\/12\/SS-react_den.cub.jvxl translucent;');\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-react1.jpg\" alt=\"Click for  3D\" width=\"280\" height=\"328\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-react1.jpg 280w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-react1-256x300.jpg 256w\" sizes=\"auto, (max-width: 280px) 100vw, 280px\" \/><p id=\"caption-attachment-13196\" class=\"wp-caption-text\">Click for 3D<\/p><\/div>\n<div id=\"attachment_13195\" style=\"width: 337px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-13195\" class=\"size-full wp-image-13195\" onclick=\"jmolInitialize('..\/Jmol\/');jmolSetAppletColor('white');jmolApplet([450,450],'load wp-content\/uploads\/2014\/12\/SS-prod_den.cub.xyz;isosurface colour red blue wp-content\/uploads\/2014\/12\/SS-prod_den.cub.jvxl translucent;');\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-prod1.jpg\" alt=\"Click for  3D\" width=\"327\" height=\"272\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-prod1.jpg 327w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/SS-prod1-300x249.jpg 300w\" sizes=\"auto, (max-width: 327px) 100vw, 327px\" \/><p id=\"caption-attachment-13195\" class=\"wp-caption-text\">Click for 3D<\/p><\/div>\n<h2>References<\/h2>\n    <ol class=\"kcite-bibliography csl-bib-body\"><li id=\"ITEM-13174-0\">H.E. Simmons, and R.D. Smith, \"A NEW SYNTHESIS OF CYCLOPROPANES FROM OLEFINS\", <i>Journal of the American Chemical Society<\/i>, vol. 80, pp. 5323-5324, 1958. <a href=\"https:\/\/doi.org\/10.1021\/ja01552a080\">https:\/\/doi.org\/10.1021\/ja01552a080<\/a>\n\n<\/li>\n<li id=\"ITEM-13174-1\">H.S. Rzepa, \"C 3 H 6 I 2 Zn 1\", 2014. <a href=\"https:\/\/doi.org\/10.14469\/ch\/147617\">https:\/\/doi.org\/10.14469\/ch\/147617<\/a>\n\n<\/li>\n<li id=\"ITEM-13174-2\">H.S. Rzepa, \"Gaussian Job Archive for C3H6I2Zn\", 2014. <a href=\"https:\/\/doi.org\/10.6084\/m9.figshare.1270441\">https:\/\/doi.org\/10.6084\/m9.figshare.1270441<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> <!-- kcite-section 13174 -->","protected":false},"excerpt":{"rendered":"<p>These posts contain the computed potential energy surfaces for a fair few &#8220;text-book&#8221; reactions. Here I chart the course of the cyclopropanation of alkenes using the Simmons-Smith reagent, as\u00a0prepared from di-iodomethane using zinc metal insertion into a C-I bond. Two reactions it can be compared with are the epoxidation of ethene using a peracid and [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1086],"tags":[1302,1303,1304],"ppma_author":[2661],"class_list":["post-13174","post","type-post","status-publish","format-standard","hentry","category-reaction-mechanism-2","tag-computed-potential-energy-surfaces","tag-di-iodomethane-using-zinc-metal-insertion","tag-simmons"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Cyclopropanation: the mechanism of the Simmons\u2013Smith reaction. - Henry Rzepa&#039;s Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13174\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Cyclopropanation: the mechanism of the Simmons\u2013Smith reaction. - Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"og:description\" content=\"These posts contain the computed potential energy surfaces for a fair few &#8220;text-book&#8221; reactions. Here I chart the course of the cyclopropanation of alkenes using the Simmons-Smith reagent, as\u00a0prepared from di-iodomethane using zinc metal insertion into a C-I bond. Two reactions it can be compared with are the epoxidation of ethene using a peracid and [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13174\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"article:published_time\" content=\"2014-12-14T08:07:50+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2014-12-14T08:48:06+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/12\/simmonds-smith.svg\" \/>\n<meta name=\"author\" content=\"Henry Rzepa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Henry Rzepa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Cyclopropanation: the mechanism of the Simmons\u2013Smith reaction. - Henry Rzepa&#039;s Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13174","og_locale":"en_GB","og_type":"article","og_title":"Cyclopropanation: the mechanism of the Simmons\u2013Smith reaction. - Henry Rzepa&#039;s Blog","og_description":"These posts contain the computed potential energy surfaces for a fair few &#8220;text-book&#8221; reactions. 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Here I take a look at the NMR spectra of the resulting cyclopropane products, with an evaluation of the original stereochemical assignments. Three products were identified, 4a-c\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":14601,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=14601","url_meta":{"origin":13174,"position":1},"title":"Yes, no, yes. Computational mechanistic exploration of (nickel-catalysed) cyclopropanation using tetramethylammonium triflate.","author":"Henry Rzepa","date":"October 1, 2015","format":false,"excerpt":"A fascinating re-examination has appeared of a reaction first published in 1960 by Wittig and then repudiated by him in 1964 since it could not be replicated by a later student. According to the new work, the secret to a successful replication\u00a0seems to be\u00a0the presence of traces of a nickel\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":11966,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=11966","url_meta":{"origin":13174,"position":2},"title":"Intersecting paths in molecular energy surfaces.","author":"Henry Rzepa","date":"February 16, 2014","format":false,"excerpt":"The potential energy surface for a molecule tells us about how it might react. These surfaces have been charted for thousands of reactions using quantum mechanics, and their basic features are thought to be well understood. Coming across an entirely new feature is rare. So what do you make of\u2026","rel":"","context":"In &quot;pericyclic&quot;","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"ylid","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2014\/02\/ylid.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":8174,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8174","url_meta":{"origin":13174,"position":3},"title":"Mechanisms of carbon monoxide insertion reactions: A reality check on carbonylation of methyl manganese pentacarbonyl","author":"Henry Rzepa","date":"November 4, 2012","format":false,"excerpt":"When methyl manganese pentacarbonyl is treated with carbon monoxide in e.g. di-n-butyl ether, acetyl manganese pentacarbonyl is formed. This classic experiment conducted by Cotton (of quadruple bond fame) and Calderazzo in 1962 dates from an era when chemists conducted extensive kinetic analyses to back up any mechanistic speculations. Their suggested\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/11\/CO%2Bethene.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":8246,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8246","url_meta":{"origin":13174,"position":4},"title":"Thalidomide. The role of water in the mechanism of its aqueous racemisation.","author":"Henry Rzepa","date":"November 10, 2012","format":false,"excerpt":"Thalidomide is a chiral molecule, which was sold in the 1960s as a sedative in its (S,R)-racemic form. The tragedy was that the (S)-isomer was tetragenic, and only the (R) enantiomer acts as a sedative. What was not appreciated at the time is that interconversion of the (S)- and (R)\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/11\/thal1.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":13047,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13047","url_meta":{"origin":13174,"position":5},"title":"A computed mechanistic pathway for the formation of an amide from an acid and an amine in non-polar solution.","author":"Henry Rzepa","date":"November 12, 2014","format":false,"excerpt":"In London, one has the pleasures of attending occasional one day meetings at the Burlington House, home of the Royal Society of Chemistry. On November 5th this year, there was an excellent\u00a0meeting on the topic of Challenges in Catalysis,\u00a0and you can see the speakers and (some of) their slides here.\u2026","rel":"","context":"In &quot;reaction mechanism&quot;","block_context":{"text":"reaction mechanism","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1086"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13174","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=13174"}],"version-history":[{"count":21,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13174\/revisions"}],"predecessor-version":[{"id":13202,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/13174\/revisions\/13202"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13174"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13174"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13174"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=13174"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}