(Trialkylsilyl)vinylketenes: Synthesis and Application as Diene Components in Diels−Alder Cycloadditions
摘要:
New strategies for the synthesis of (trialkylsilyl)vinylketenes ("TAS-vinylketenes") are described based on the photochemical Wolff rearrangement of alpha-silyl-alpha'-diazo-alpha,beta-unsaturated ketones and the 4 pi electrocyclic ring opening of cyclobutenones. These remarkably robust vinylketenes undergo highly regioselective [4 + 2] cycloadditions with reactive olefinic and acetylenic dienophiles to produce highly substituted cyclohexenones and phenols in which the ketene carbonyl dominates in controlling the regiochemical course of the reaction. The stereochemical course of these cycloadditions follows the Alder endo rule, as illustrated in the reaction of nitropropene with TBS-vinylketene 22.
Rearrangement of an Intermediate Cyclopropyl Ketene in a Rh<sup>II</sup>-Catalyzed Formal [4 + 1]-Cycloaddition Employing Vinyl Ketenes as 1,4-Dipoles and Donor–Acceptor Metallocarbenes
作者:Kevin X. Rodriguez、Nicolai Kaltwasser、Tiffany A. Toni、Brandon L. Ashfeld
DOI:10.1021/acs.orglett.7b00618
日期:2017.5.19
formal [4 + 1]-cycloaddition approach toward spirooxindole cyclopentenones is described. The diastereoselective cyclopropanation of vinyl ketenes with diazooxindoles as C1 synthons initiated a relatively mild formal [1,3]-migration of an intermediate cyclopropyl ketene to provide spirooxindoles in good to excellent yields (36–99%).
An unusual stereoretentive 1,3-quaternary carbon shift resulting in an enantioselective Rh<sup>II</sup>-catalyzed formal [4+1]-cycloaddition between diazo compounds and vinyl ketenes
作者:Kevin X. Rodriguez、Tara C. Pilato、Brandon L. Ashfeld
DOI:10.1039/c8sc00020d
日期:——
Enantioselective quaternary carbon construction in the assembly of cyclopentenones employing a RhII-catalyzed, formal [4+1]-cycloaddition is described. A Rh2(S-TCPTTL)4-catalyzed cyclopropanation of a vinyl ketene with a disubstituted diazo compound initiates a stereoretentive, accelerated ring expansion to provide the cycloadduct in good to excellent yields and enantioselectivity.
描述了采用 Rh II催化的正式 [4+1]-环加成反应组装环戊烯酮时的对映选择性季碳结构。Rh 2 ( S -TCPTTL) 4催化的乙烯基烯酮与二取代的重氮化合物的环丙烷化引发立构保留、加速环扩张,从而以良好至优异的产率和对映选择性提供环加合物。