{"id":5716,"date":"2011-11-29T07:16:14","date_gmt":"2011-11-29T07:16:14","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=5716"},"modified":"2011-11-30T09:54:33","modified_gmt":"2011-11-30T09:54:33","slug":"a-modern-take-on-pericyclic-sigmatropic-migrations","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5716","title":{"rendered":"A modern take on pericyclic sigmatropic migrations."},"content":{"rendered":"
\n

Another common type of pericyclic reaction is the migration of hydrogen or carbon along a conjugated chain, as in the [1,3] migration of a carbon as shown below. As before<\/a>, I explore the stereochemistry of the thermal and photochemical reactions.<\/p>\n

\"\"<\/a><\/p>\n

The reaction is known to proceed <\/a>thermally\u00a0with inversion of configuration<\/em> at the migrating carbon, and constitutes a 4n-electron reaction involving one antarafacial<\/em> component (at that carbon). As usual, the thermal reaction can be rationalised by its transition state and an accompanying IRC<\/a>.<\/p>\n

\"\"

IRC for the thermal migration of a carbon. Click for 3D.<\/p><\/div>The photochemical reaction (not hitherto studied as far as I know) has a conical intersection<\/a> between the S1<\/sub> and S0<\/sub> states which clearly displays migration of the carbon with retention<\/em> (suprafacially<\/em>).<\/p>\n

\"\"

Photochemically induced 1,3 migration with retention of configuration. Click for 3D<\/p><\/div>I conclude this trio of pericyclic reactions with a re-affirmation of the general rules for such reactions, which state that changing the reaction conditions from heat to light is likely invert one suprafacial or antarafacial stereochemical component, \u00a0located either on the transition state (for the thermal reaction) or the conical intersection (for the photochemical equivalent). A caveat is necessary, in that the pathways for photochemical reactions are generally more complex than thermal ones, and so exceptions to this broad statement may well be easy to find.<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

Another common type of pericyclic reaction is the migration of hydrogen or carbon along a conjugated chain, as in the [1,3] migration of a carbon as shown below. As before, I explore the stereochemistry of the thermal and photochemical reactions. The reaction is known to proceed thermally\u00a0with inversion of configuration at the migrating carbon, and […]<\/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":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[],"tags":[2650,373],"ppma_author":[2661],"class_list":["post-5716","post","type-post","status-publish","format-standard","hentry","tag-pericyclic","tag-tutorial-material"],"yoast_head":"\nA modern take on pericyclic sigmatropic migrations. - Henry Rzepa'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=5716\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"A modern take on pericyclic sigmatropic migrations. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"Another common type of pericyclic reaction is the migration of hydrogen or carbon along a conjugated chain, as in the [1,3] migration of a carbon as shown below. As before, I explore the stereochemistry of the thermal and photochemical reactions. The reaction is known to proceed thermally\u00a0with inversion of configuration at the migrating carbon, and […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5716\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2011-11-29T07:16:14+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2011-11-30T09:54:33+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/11\/sigma.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":"A modern take on pericyclic sigmatropic migrations. - Henry Rzepa'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=5716","og_locale":"en_GB","og_type":"article","og_title":"A modern take on pericyclic sigmatropic migrations. - Henry Rzepa's Blog","og_description":"Another common type of pericyclic reaction is the migration of hydrogen or carbon along a conjugated chain, as in the [1,3] migration of a carbon as shown below. As before, I explore the stereochemistry of the thermal and photochemical reactions. 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It all boils down to\u2026","rel":"","context":"In \"pericyclic\"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=pericyclic"},"img":{"alt_text":"","src":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/01\/pericyclic-tutorial_s.svg","width":350,"height":200},"classes":[]},{"id":9090,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=9090","url_meta":{"origin":5716,"position":4},"title":"A conflation of concepts: Conformation and pericyclic.","author":"Henry Rzepa","date":"January 10, 2013","format":false,"excerpt":"This is an interesting result I got when studying the [1,4] sigmatropic rearrangement of\u00a0heptamethylbicyclo-[3.1.0]hexenyl cations. It fits into the last lecture of a series on pericyclic mechanisms, and just before the first lecture on conformational analysis. This is how they join. 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He had constructed a model of the reaction he wanted to undertake, perhaps with\u2026","rel":"","context":"In "Historical"","block_context":{"text":"Historical","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=565"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/01\/sden.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"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\/5716","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=5716"}],"version-history":[{"count":27,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5716\/revisions"}],"predecessor-version":[{"id":5761,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5716\/revisions\/5761"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5716"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5716"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5716"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=5716"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}