NHC-Catalyzed Enantioselective Dearomatizing Hydroacylation of Benzofurans and Benzothiophenes for the Synthesis of Spirocycles

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• 作者：Daniel Janssen-Müller ; Mirco Fleige ; Danny Schlüns ; Marco Wollenburg ; Constantin G. Daniliuc ; Johannes Neugebauer ; Frank Glorius
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：September 2, 2016
• 年：2016
• 卷：6
• 期：9
• 页码：5735-5739
• 全文大小：412K
• 年卷期：0
• ISSN：2155-5435

文摘

Benzofurans and benzothiophenes have been efficiently employed as substrates in an enantioselective intramolecular hydroacylation. Breaking aromaticity in a 5-exo-trig cyclization of easily accessible heteroarenes by NHC-catalyzed hydroacylation gives access to a simple class of mainly unexplored spirocycles with up to 99% enantiomeric excess (ee). The formed product class bears interesting three-dimensional pseudoaxial chirality and shows typical ketone reactivity. Density functional theory (DFT) calculations reveal erosion of the ee via a stepwise mechanism bearing a hetero Wheland intermediate. Theoretical data are in agreement with deuterium-labeling studies and a linear correlation between electronics (σ) and the ee.