Development of a Method for the Reductive Cyclization of Enones by a Titanium Catalyst

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• 作者：Natasha M. Kablaoui and and Stephen L. Buchwald
• 刊名：Journal of the American Chemical Society
• 出版年：1996
• 出版时间：April 3, 1996
• 年：1996
• 卷：118
• 期：13
• 页码：3182 - 3191
• 全文大小：582K
• 年卷期：v.118,no.13(April 3, 1996)
• ISSN：1520-5126

文摘

An effective protocol in whichbis(trimethylphosphine)titanocene is used to catalyze thereductive cyclizationof enones to cyclopentanols via a metallacyclic intermediate has beendeveloped. The key step in the process is thecleavage of the titanium-oxygen bond in the metallacycle by a silaneto regenerate the catalyst. Mechanistic aspectsof the reaction are discussed and the diastereoselectivity of thetransformation is studied using both achiral andchiral substrates. The scope and limitations of the procedure aredescribed. An in situ protocol for thegenerationof the air- and moisture-sensitive catalyst has also been developed.This work demonstrates, for the first time, theviability of using an early transition metal complex to catalyze thereductive cyclization of an alkene with a heteroatom-containing functional group.