{"id":7434,"date":"2012-08-06T14:01:21","date_gmt":"2012-08-06T13:01:21","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=7434"},"modified":"2012-12-29T17:18:31","modified_gmt":"2012-12-29T17:18:31","slug":"the-curtius-rearrangement-one-step-or-two","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7434","title":{"rendered":"The Curtius rearrangement. One step or two?"},"content":{"rendered":"
\n

The Curtius reaction is represented in most chemistry texts and notes as following path (a) below. It is one of a general class of thermally induced rearrangement which might be described as elimination\/migration (in a sense similar to this ring contraction migration\/elimination<\/a>), in this case implicating a nitrene intermediate if the two steps occur consecutively. Wikipedia is normally very much on the ball with this sort of thing, and a comment about the reaction mechanism<\/a> there notes that current evidence prefers route (b), avoiding nitrene intermediacy (and hence formally removing this from examples of nitrene reactions).<\/p>\n

\"\"<\/p>\n

So time for a reality check (which in this case takes the form of a \u03c9B97XD\/6-311G(d,p)\/SCRF=dichloromethane calculation).\u00a0<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

This is pretty clear-cut; no nitrene intermediate. Now for the standard text-books to catch up!<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

The Curtius reaction is represented in most chemistry texts and notes as following path (a) below. It is one of a general class of thermally induced rearrangement which might be described as elimination\/migration (in a sense similar to this ring contraction migration\/elimination), in this case implicating a nitrene intermediate if the two steps occur consecutively. […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_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},"jetpack_post_was_ever_published":false},"categories":[],"tags":[902,901,2650,843,373],"ppma_author":[2661],"class_list":["post-7434","post","type-post","status-publish","format-standard","hentry","tag-elimination","tag-migration","tag-pericyclic","tag-reaction-mechanism","tag-tutorial-material"],"yoast_head":"\nThe Curtius rearrangement. One step or two? - 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=7434\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The Curtius rearrangement. One step or two? - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"The Curtius reaction is represented in most chemistry texts and notes as following path (a) below. It is one of a general class of thermally induced rearrangement which might be described as elimination\/migration (in a sense similar to this ring contraction migration\/elimination), in this case implicating a nitrene intermediate if the two steps occur consecutively. […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7434\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2012-08-06T13:01:21+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2012-12-29T17:18:31+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/08\/curtius.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":"The Curtius rearrangement. One step or two? - 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=7434","og_locale":"en_GB","og_type":"article","og_title":"The Curtius rearrangement. One step or two? - Henry Rzepa's Blog","og_description":"The Curtius reaction is represented in most chemistry texts and notes as following path (a) below. It is one of a general class of thermally induced rearrangement which might be described as elimination\/migration (in a sense similar to this ring contraction migration\/elimination), in this case implicating a nitrene intermediate if the two steps occur consecutively. […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7434","og_site_name":"Henry Rzepa's Blog","article_published_time":"2012-08-06T13:01:21+00:00","article_modified_time":"2012-12-29T17:18:31+00:00","og_image":[{"url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/08\/curtius.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7434#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7434"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"The Curtius rearrangement. 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Both stereochemical modes are known to occur, depending on the leaving group, solvent and\u2026","rel":"","context":"In "reaction mechanism"","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":[]},{"id":6279,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=6279","url_meta":{"origin":7434,"position":2},"title":"E2 elimination vs ring contraction: anti-periplanarity in action.","author":"Henry Rzepa","date":"February 20, 2012","format":false,"excerpt":"The anti-periplanar principle permeates organic reactivity. Here I pick up on an example of the antiperiplanar E2 elimination (below, blue) by comparing it to a competing reaction involving a [1,2] antiperiplanar migration (red). The relative rates of these two processes will depend on several factors such as the ability of\u2026","rel":"","context":"In \"conformational analysis\"","block_context":{"text":"conformational analysis","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=conformational-analysis"},"img":{"alt_text":"","src":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/02\/Ring.svg","width":350,"height":200},"classes":[]},{"id":8961,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8961","url_meta":{"origin":7434,"position":3},"title":"The mechanism of the Benzidine rearrangement.","author":"Henry Rzepa","date":"January 6, 2013","format":false,"excerpt":"The benzidine rearrangement is claimed to be an example of the quite rare\u00a0[5,5] sigmatropic migration, which is a ten-electron homologation of the very common [3,3] sigmatropic reaction (e.g. the Cope or Claisen). Some benzidine rearrangements are indeed thought to go through the [3,3] route. The topic has been reviewed here.\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"NCI surface. Click for 3D.","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/01\/benzidinenci.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":14944,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=14944","url_meta":{"origin":7434,"position":4},"title":"A tutorial problem in stereoelectronic control. A Grob alternative to the Tiffeneau-Demjanov rearrangement?","author":"Henry Rzepa","date":"November 28, 2015","format":false,"excerpt":"In answering tutorial problems, students often need skills in deciding how much time to spend on explaining what does not happen, as well as what does. Here I explore alternatives to the mechanism outlined in the previous post to see what computation\u00a0has to say about what does (or might) not\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"Alt1","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2015\/11\/Alt1.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":6618,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=6618","url_meta":{"origin":7434,"position":5},"title":"The mechanism of the Baeyer-Villiger rearrangement.","author":"Henry Rzepa","date":"May 7, 2012","format":false,"excerpt":"The Baeyer-Villiger rearrangement was named after its discoverers, who in\u00a01899\u00a0described the transformation of menthone into the corresponding lactone using Caro's acid (peroxysulfuric acid). The mechanism is described in all text books of organic chemistry as involving an alkyl migration. Here I take a look at the scheme described by\u00a0Alvarez-Idaboy, Reyes\u2026","rel":"","context":"In "reaction mechanism"","block_context":{"text":"reaction mechanism","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1086"},"img":{"alt_text":"","src":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/05\/bv1.svg","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\/7434","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=7434"}],"version-history":[{"count":9,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/7434\/revisions"}],"predecessor-version":[{"id":7443,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/7434\/revisions\/7443"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7434"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7434"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7434"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=7434"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}