Nucleophilic Halogenation of Cyclic Nitronates: A General Access to 3-Halo-1,2-Oxazines
作者:Roman S. Malykhin、Aleksandr O. Kokuev、Valentin S. Dorokhov、Yulia V. Nelyubina、Vladimir A. Tartakovsky、Andrey A. Tabolin、Sema L. Ioffe、Alexey Yu. Sukhorukov
DOI:10.1021/acs.joc.9b02010
日期:2019.11.1
In this article, comprehensive studies on the nucleophilic chlorination and bromination of readily available six-membered cyclic nitronates (1,2-oxazine-N-oxides) are reported. Under optimized conditions (POCl3 or (COBr)2 with Hünig's base), 3-halo-substituted 1,2-oxazines, which are difficult to access by other routes, were obtained in good to high yields. The latter were shown to be convenient precursors
Catalytic Enantioselective Synthesis of Quaternary Stereocenters via Intermolecular C-Acylation of Silyl Ketene Acetals: Dual Activation of the Electrophile and the Nucleophile
作者:Ara H. Mermerian、Gregory C. Fu
DOI:10.1021/ja028554k
日期:2003.4.1
A nucleophile-catalyzed asymmetric intermolecular C-acylation of silylketeneacetals by anhydrides has been developed, furnishing quaternary stereocenters with high enantioselectivity. Mechanistic studies support the hypothesis that the reaction involves activation both of the silylketeneacetal (generation of an enolate) and of the anhydride (formation of an acylpyridinium ion).