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Diarylprolinol Silyl Ether Catalyzed Asymmetric Friedel–Crafts Alkylation of Indoles with α,β‐Unsaturated Aldehydes: Enhanced Enantioselectivity and Mechanistic Investigations
Author(s) -
Shi ZiHui,
Sheng Hao,
Yang KeFang,
Jiang JianXiong,
Lai GuoQiao,
Lu Yixin,
Xu LiWen
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001404
Subject(s) - chemistry , friedel–crafts reaction , enantioselective synthesis , lewis acids and bases , silylation , steric effects , stereoselectivity , aldehyde , organocatalysis , alkylation , substrate (aquarium) , organic chemistry , catalysis , amine gas treating , silyl ether , brønsted–lowry acid–base theory , oceanography , geology
Abstract A highly enantioselective Friedel–Crafts alkylation of indoles with α,β‐unsaturated aldehydes with excellent enantioselectivities (up to >99 % ee ) has been developed, and this improved method offers substantial advantages over traditional approaches, not only by avoiding the use of acids or bases, but also in terms of the higher level of stereoselectivity. In addition, we have demonstrated through a plausible mechanism that the role of silicon in the diarylprolinol silyl ethers (Jørgensen–Hayashi organocatalyst) not only serves as a bulky group to induce steric repulsion but also serves as a Lewis acidic promoter to accelerate the reaction between the secondary amine and the substrate (α , β‐unsaturated aldehyde).