Brønsted Acid-Promoted Cyclizations of Siloxyalkynes with Arenes and Alkenes
作者:Liming Zhang、Sergey A. Kozmin
DOI:10.1021/ja046586x
日期:2004.8.1
We have described the first Brønsted acid-mediated cyclizations of siloxyalkynes with simple arenes and alkenes to afford substituted tetralone and cyclohexenone derivatives. The most notable aspect of the carbocyclizations involving siloxyalkynes is the ability to employ a range of substrates that are not restricted to those containing electron-rich arenes and alkenes. The key mechanistic feature of the reaction is the generation of a highly reactive ketenium ion upon protonation of siloxyalkyne. We believe that the low nucleophilicty of the counteranion is crucial for enabling the formation and effective interception of this highly reactive intermediate.
Reactions of (Trialkylsilyl)vinylketenes with Lithium Ynolates: A New Benzannulation Strategy
作者:Wesley F. Austin、Yongjun Zhang、Rick L. Danheiser
DOI:10.1021/ol051307b
日期:2005.9.1
(Trialkylsilyl)vinylketenes react with lithium ynolates to produce highly substituted phenols in a new benzannulation strategy that proceeds via the 6 pi electrocyclization of an intermediate 3-(oxido)dienylketene.