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Asymmetric Synthesis of Chiral Pyrrolizine‐Based Triheterocycles by Organocatalytic Cascade Aza‐Michael–Aldol Reactions
Author(s) -
Lee HyoJun,
Cho ChangWoo
Publication year - 2014
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.201301260
Subject(s) - stereocenter , aldol reaction , chemistry , cascade , enantioselective synthesis , michael reaction , cascade reaction , organocatalysis , combinatorial chemistry , trifluoromethyl , organic chemistry , stereochemistry , catalysis , alkyl , chromatography
New, chiral pyrrolizine‐based triheterocycles were obtained by the organocatalytic asymmetric cascade aza‐Michael–aldol reaction of α‐branched α,β‐unsaturated aldehydes with 2‐(trifluoroacetyl)pyrroles. High enantioselectivities (90–95 % ee ) and excellent diastereoselectivities ( dr up to >20:1) were achieved by employing this synthetic strategy. The highly functionalized, trifluoromethyl‐substituted cascade products have three consecutive stereogenic centers that include two chiral quaternary centers. The chemoselective stepwise Suzuki cross‐coupling reaction of the cascade products with two different arylboronic acids provided chiral pyrrolizine‐based triheterocycles that contain two distinct aryl substituents in good yields.