ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic and Theoretical Studies of Ring Closure of Unstabilized Bisketenes to CyclobutenedionesAnnette D. Allen, Jim D. Colomvakos, Ian Egle, Janusz Lusztyk, Michael A. McAllister, Thomas T. Tidwell, Brian D. Wagner, and Da-chuan ZhaoCite this: J. Am. Chem. Soc. 1995, 117, 28, 7552–7553Publication Date (Print):July 1, 1995Publication History Published online1 May 2002Published inissue 1 July 1995https://pubs.acs.org/doi/10.1021/ja00133a032https://doi.org/10.1021/ja00133a032research-articleACS PublicationsRequest reuse permissionsArticle Views147Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Silyl substituents stabilize ketenes, and permit the preparation of persistent bisketenes, which show characteristic 13 C, 17 O, and 29 Si NMR chemical shifts. The structures and conformations of bisketenes have been examined, as well as their interconversion with cyclobutenediones. A tetraketene has been prepared, and the hydration reactivity of carbon suboxide has been measured. Key words: bisketenes, structures and conformations; cyclobutenedione interconversion.
The interconversion of cyclobutene-1,2-diones (1) and 1,2-bisketenes (RCCO)2 (2) has been surveyed for different combinations of substituents R = H, Me, t-Bu, Ph, Me3Si, CN, Cl, Br, R1O, alkynyl, and PhS. The bisketenes 2 have been generated by flash photolysis, and the kinetics of their conversion to 1 have been studied by time-resolved infrared and ultraviolet spectroscopy. The rate constants of the ring closure of 2 are correlated by the ketene stabilization parameters (SE) and with calculated barriers. The rate constant of ring closure of the di-tert-butyl bisketene 2g to cyclobutenedione 1g is only 40 times smaller than for the dimethyl analogue, showing a rather modest steric barrier. The quinoketene 2s has a fast rate of ring closure, but not as fast as anticipated on the basis of calculated geometric and thermodynamic factors. A lag in the attainment of aromatic stabilization in the transition structure for ring closure is a possible cause of this diminished reactivity.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT9-(Trifluoromethyl)fluorenyl Cation: A New Doubly Destabilized CarbocationAnnette D. Allen, Jim D. Colomvakos, Oswald S. Tee, and Thomas T. TidwellCite this: J. Org. Chem. 1994, 59, 24, 7185–7187Publication Date (Print):December 1, 1994Publication History Published online1 May 2002Published inissue 1 December 1994https://pubs.acs.org/doi/10.1021/jo00103a001https://doi.org/10.1021/jo00103a001research-articleACS PublicationsRequest reuse permissionsArticle Views224Altmetric-Citations36LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Cycloaddition reactions of the bisketenes OCC(SiMe3)CRCO (15, R = SiMe3; 16, R = Ph) include BF3-catalyzed [2+2] cycloaddition of 15 with CH3CHO to form an isolable β-lactone 18 adduct which undergoes thermal decarboxylation to the vinylketene 19. Reactions of 15 and 16 with CH2N2 proceed by [4+1] cycloaddition to give mixtures of cyclopentene-1,3-diones 20 and methylenefuranones 21, while Me3SiCHN2 and PhCHN2 give only 20. The reactions are interpreted in terms of a steric preference for nucleophilic attack by the substituted diazomethanes from the side of the ketene bearing the Me3SiCCO substituent, leading to formation of 20. With the less bulky CH2N2, attack occurs from both sides and approach from the side of the R group leads to formation of lactones 21. Reaction of tetramethoxyethylene with 15 yields both a cyclopentene-1,3-dione 24 from net addition of dimethoxycarbene and a spirocyclopropylbutenolide 25. Free dimethoxycarbene generated by heating an oxadiazoline precursor also reacted with 15 to give dione 24. Various electrophilic dienophiles do not react with 15, but nucleophilic alkynes react with 16 in thermal reactions to give spirocyclopropenylfuranones 33−36, and Me3SiC⋮COEt and 16 react by net [4 + 2] cycloaddition to give the quinone 37 as the major product.
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