{"id":25633,"date":"2022-09-30T15:40:22","date_gmt":"2022-09-30T14:40:22","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=25633"},"modified":"2022-10-08T08:42:02","modified_gmt":"2022-10-08T07:42:02","slug":"a-new-type-of-bispericyclic-reaction-cyclopropanone-butadiene","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=25633","title":{"rendered":"A new type of bispericyclic reaction: Cyclopropanone + butadiene."},"content":{"rendered":"
\n

The term bispericyclic reaction was famously coined by Caramella et a<\/em>l in 2002[1]<\/a><\/span> to describe the unusual features of the apparently innocuous dimerisation of cyclopentadiene<\/a>. It shows features of two paths for different pericyclic reactions, comprising a 2+4 cycloaddition in the early stages, but evolving into a (degenerate) pair of [3,3] sigmatropic reactions in the latter stages. Houk (who also uses the term ambimodal) has in recent years extended the number of examples of such pericyclic sequences to trispericyclic[2]<\/a><\/span> (see here<\/a>) and even an ambimodel tetrapericyclic reaction, as reported at the recent WATOC event. Here I show an example of a new type of bispericyclic reaction, comprising a 2+4 cycloaddition combined with a electrocyclic ring opening.<\/p>\n

The reaction starts with cyclopropanone. This species is reported to undergo cycloaddition reactions[3]<\/a><\/span> with e.g.<\/em> furan; below is shown the scheme with butadiene.\u00a0<\/p>\n

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

Calculations at the \u03c9B97XD\/Def2-TZVPP\/SCRF=DCM were undertaken (FAIR data DOI 10.14469\/hpc\/11246<\/a>). Because it has been suggested that the “intermediate” ylid might have some biradical character, this was modelled using the option of a spin-unrestricted (UHF) method and a starting guess for the density matrix using the Gaussian keyword guess(mix), which uses a linear combination of the HOMO and LUMO to destroy \u03b1-\u03b2 and spatial symmetries. At the located transition state, the spin expectation operator <S**2>= 0.4003 and it reaches a maximum value of <S**2>= 0.7002, so this system does indeed have some biradical character (the value would be 0.000 for a closed shell system, and 1.000 for a pure biradical). The IRC is shown below.<\/p>\n

\"\"<\/p>\n

<S**2> is non-zero only between the range -2.5 to +4.5, the rest of the path has the value <S**2> =0.0. The central region of the path (IRC ~0 to +4.5) shows very small gradients, and can be characterised as the region corresponding to the ylid above acting as a “hidden intermediate”.<\/p>\n

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

The central region also coincides with an increase in the dipole moment at the start of the reaction and a decrease at the end indicating that the system also has a fair amount of zwitterionic character, as implied in the ylid structure shown above. But the dip in dipole moment at around IRC = 2 corresponds to biradical character partially replacing the charge-separated ionic mode.<\/p>\n

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

The IRC animation shown below shows that in the early stages of the reaction, electrocyclic ring opening (with disrotation) occurs, but no explicit ylid intermediate is formed. Instead the reaction continues without pause to a cycloaddition reaction for completion.<\/p>\n

\"\"<\/p>\n

One interesting question is what impact does the partial biradical character have on this outcome? Shown below are the IRC responses to a potential for which the wavefunction has <S**2> =0.0 across the entire region.<\/p>\n

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

\"\"<\/p>\n

The reaction reveals an entirely different, but still bis-pericyclic reaction involving the same electrocyclic ring opening to the ylid shown above, but then reaction as a 2+2 cycloaddition reaction via<\/em> the oxygen rather than the carbon of the ylid. The dipole moment no longer shows the biradical-induced dip in the middle, but rises to a full maximum instead.<\/p>\n

So here we see a sequential bispericyclic reaction in which the product of an initial electrocyclic pericyclic reaction is so reactive that it immediately reacts with a diene to form the final product, in an overall concerted but asynchronous reaction. Modelling this seems to be very method dependent, and the apparently correct product is only obtained if an open-shell biradical wavefunction is used. Are there more examples?<\/p>\n

\n

This post has DOI: 10.14469\/hpc\/11247<\/p>\n

\n

References<\/h2>\n
  1. P. Caramella, P. Quadrelli, and L. Toma, \"An Unexpected Bispericyclic Transition Structure Leading to 4+2 and 2+4 Cycloadducts in the <i>E<\/i><i>ndo<\/i> Dimerization of Cyclopentadiene\", Journal of the American Chemical Society<\/i>, vol. 124, pp. 1130-1131, 2002. https:\/\/doi.org\/10.1021\/ja016622h<\/a>\n\n<\/li>\n
  2. X. Xue, C.S. Jamieson, M. Garcia-Borr\u00e0s, X. Dong, Z. Yang, and K.N. Houk, \"Ambimodal Trispericyclic Transition State and Dynamic Control of Periselectivity\", Journal of the American Chemical Society<\/i>, vol. 141, pp. 1217-1221, 2019. https:\/\/doi.org\/10.1021\/jacs.8b12674<\/a>\n\n<\/li>\n
  3. H.H. Wasserman, D.R. Berdahl, and T. Lu, \"The Chemistry of Cyclopropanones\", Cyclopropyl Group Volume 1 and Volume 2 (1987)<\/i>, pp. 1455-1532, . https:\/\/doi.org\/10.1002\/0470023449.ch23<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    The term bispericyclic reaction was famously coined by Caramella et al in 2002 to describe the unusual features of the apparently innocuous dimerisation of cyclopentadiene. It shows features of two paths for different pericyclic reactions, comprising a 2+4 cycloaddition in the early stages, but evolving into a (degenerate) pair of [3,3] sigmatropic reactions in the […]<\/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":[],"ppma_author":[2661],"class_list":["post-25633","post","type-post","status-publish","format-standard","hentry","category-reaction-mechanism-2"],"yoast_head":"\nA new type of bispericyclic reaction: Cyclopropanone + butadiene. - 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=25633\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"A new type of bispericyclic reaction: Cyclopropanone + butadiene. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"The term bispericyclic reaction was famously coined by Caramella et al in 2002 to describe the unusual features of the apparently innocuous dimerisation of cyclopentadiene. It shows features of two paths for different pericyclic reactions, comprising a 2+4 cycloaddition in the early stages, but evolving into a (degenerate) pair of [3,3] sigmatropic reactions in the […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=25633\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2022-09-30T14:40:22+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2022-10-08T07:42:02+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2022\/09\/bispericyclic.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=\"3 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"A new type of bispericyclic reaction: Cyclopropanone + butadiene. - 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=25633","og_locale":"en_GB","og_type":"article","og_title":"A new type of bispericyclic reaction: Cyclopropanone + butadiene. - Henry Rzepa's Blog","og_description":"The term bispericyclic reaction was famously coined by Caramella et al in 2002 to describe the unusual features of the apparently innocuous dimerisation of cyclopentadiene. 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Soc. Special Publications (Aromaticity), 1967, 21, 217-249), where all might not be what it seems. Woodward notes that the reaction between the (highly reactive) 1 does not occur. This is attributed to it being a disallowed \u03c06 +\u2026","rel":"","context":"In \"free energy barrier\"","block_context":{"text":"free energy barrier","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=free-energy-barrier"},"img":{"alt_text":"w2+2+2","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/05\/w2%2B2%2B2.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":7389,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7389","url_meta":{"origin":25633,"position":1},"title":"Cyclopentadiene: a hydrocarbon at the crossroads of …","author":"Henry Rzepa","date":"July 29, 2012","format":false,"excerpt":"organic chemistry. It does not look like much, but this small little molecule brought us ferrocene, fluxional NMR, aromatic anions and valley-ridge inflexion points. You might not have heard of this last one, but in fact I mentioned the phenomenon in my post on nitrosobenzene. As for being at a\u2026","rel":"","context":"In \"dimer product\"","block_context":{"text":"dimer product","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=dimer-product"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/07\/cpd2.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":22774,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=22774","url_meta":{"origin":25633,"position":2},"title":"Trimerous pericyclic reactions.","author":"Henry Rzepa","date":"October 8, 2020","format":false,"excerpt":"I occasionally spot an old blog that emerges, if only briefly, as \"trending\". In this instance, only the second blog I ever wrote here, way back in 2009 as a follow up to this article. With something of that age, its always worth revisiting to see if any aspect needs\u2026","rel":"","context":"In "Curly arrows"","block_context":{"text":"Curly arrows","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2327"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2020\/10\/10-1024x671.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":5763,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5763","url_meta":{"origin":25633,"position":3},"title":"So near and yet so far. The story of the electrocyclic ring opening of a cyclohexadiene.","author":"Henry Rzepa","date":"December 6, 2011","format":false,"excerpt":"My previous three posts set out my take on three principle categories of pericyclic reaction. Here I tell a prequel to the understanding of these reactions. In 1965, Woodward and Hoffmann in their theoretical analysis (submitted Nov 30, 1964) for which the Nobel prize (to Hoffmann only of the pair,\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":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/ht.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":9,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=9","url_meta":{"origin":25633,"position":4},"title":"A Disrotatory 4n+2 electron anti-aromatic M\u00f6bius transition state for a thermal electrocyclic reaction.","author":"Henry Rzepa","date":"April 2, 2009","format":false,"excerpt":"Mauksch and Tsogoeva have recently published an article illustrating how a thermal electrocyclic reaction can proceed with distoratory ring closure, whilst simultaneously also exhibiting 4n electron M\u00f6bius-aromatic character. Why is this remarkable? Because the simple Woodward-Hoffmann rules state that a disrotatory thermal electrocyclic reaction should proceed via a H\u00fcckel-aromatic 4n+2\u2026","rel":"","context":"In "pericyclic"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"Electrocylization of [14] annulene","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/04\/p322.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":11642,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=11642","url_meta":{"origin":25633,"position":5},"title":"Avoided (pericyclic) anti-aromaticity: Reactions of t-butyl-hydroxycarbene.","author":"Henry Rzepa","date":"November 13, 2013","format":false,"excerpt":"Not long ago, I described a cyclic carbene in which elevating the carbene lone pair into a \u03c0-system transformed it from a formally 4n-antiaromatic \u03c0-cycle into a 4n+2 aromatic \u03c0-cycle. From an entirely different area of chemistry, another example of this behaviour emerges; Schreiner's trapping and reactions of t-butyl-hydroxycarbene, as\u2026","rel":"","context":"In "pericyclic"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"H-mig","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/11\/H-mig.gif?resize=350%2C200","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\/25633","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=25633"}],"version-history":[{"count":18,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/25633\/revisions"}],"predecessor-version":[{"id":25661,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/25633\/revisions\/25661"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=25633"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25633"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25633"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=25633"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}