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Pyrrolidinyl-camphor derivatives as a new class of organocatalyst for direct asymmetric Michael addition of aldehydes and ketones to beta-nitroalkenes.

Chemistry (Weinheim an der Bergstrasse, Germany) (2010-05-11)
Ying-Fang Ting, Chihliang Chang, Raju Jannapu Reddy, Dhananjay R Magar, Kwunmin Chen
ABSTRACT

Practical and convenient synthetic routes have been developed for the synthesis of a new class of pyrrolidinyl-camphor derivatives (7 a-h). These novel compounds were screened as catalysts for the direct Michael addition of symmetrical alpha,alpha-disubstituted aldehydes to beta-nitroalkenes. When this asymmetric transformation was catalyzed by organocatalyst 7 f, the desired Michael adducts were obtained in high chemical yields, with high to excellent stereoselectivities (up to 98:2 diastereomeric ratio (d.r.) and 99 % enantiomeric excess (ee)). The scope of the catalytic system was expanded to encompass various aldehydes and ketones as the donor sources. The synthetic application was demonstrated by the synthesis of a tetrasubstituted-cyclohexane derivative from (S)-citronellal, with high stereoselectivity.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
(±)-Citronellal, ≥95.0% (GC)
Sigma-Aldrich
(S)-(−)-Citronellal, 96%
Supelco
(±)-Citronellal, analytical standard
Sigma-Aldrich
(±)-Citronellal, natural, ≥85%, FCC, FG
Sigma-Aldrich
(R)-(+)-Citronellal, technical grade