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Chiral N , N ′‐Dioxide–Scandium(III) Complex‐Catalyzed Asymmetric Friedel–Crafts Alkylation Reaction of ortho ‐Hydroxybenzyl Alcohols with C3‐Substituted N‐Protected Indoles
Author(s) -
Zheng Jianfeng,
Lin Lili,
Dai Li,
Yuan Xiao,
Liu Xiaohua,
Feng Xiaoming
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201604088
Subject(s) - friedel–crafts reaction , chemistry , catalysis , alkylation , yield (engineering) , indole test , enantioselective synthesis , medicinal chemistry , lewis acids and bases , brønsted–lowry acid–base theory , organic chemistry , scandium , materials science , metallurgy
The first Lewis acid catalyzed asymmetric Friedel–Crafts alkylation reaction of ortho ‐hydroxybenzyl alcohols with C3‐substituted indoles is described. A chiral N , N ′‐dioxide Sc(OTf) 3 complex served not only to promote formation of ortho ‐quinone methides ( o ‐QMs) in situ but also induced the asymmetry of the reaction. This methodology enables a novel activation of ortho ‐hydroxybenzyl alcohols, thus affording the desired chiral diarylindol‐2‐ylmethanes in up to 99 % yield and 99 % ee . A range of functional groups were also tolerated under the mild reaction conditions. Moreover, this strategy gives concise access to enantioenriched indole‐fused benzoxocines.