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Phase‐Transfer‐Catalyzed Asymmetric Synthesis of Chiral N ‐Substituted Pyrazoles by Aza‐Michael Reaction
Author(s) -
Lee SuJeong,
Bae JuYeon,
Cho ChangWoo
Publication year - 2015
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.201500940
Subject(s) - chemistry , pyrazole , catalysis , michael reaction , enantioselective synthesis , cinchona , organic chemistry , combinatorial chemistry , medicinal chemistry
An efficient cinchona‐based phase‐transfer‐catalyzed asymmetric aza‐Michael reaction of pyrazole with various α,β‐unsaturated ketones has been developed for the preparation of chiral N ‐substituted pyrazoles. This reaction provided the desired products in good yields (up to 99 %) with excellent enantioselectivities (87–94 % ee ). In addition, the reaction of 3‐methyl‐1 H ‐pyrazole, an unsymmetrically substituted pyrazole, was treated with α,β‐unsaturated ketones to afford the corresponding chiral N ‐substituted pyrazoles in good yields (up to 99 %) with excellent enantioselectivities (90–92 % ee ) and regioisomeric ratios of up to 9:1.