Table of Contents
Organic Chemistry International
Volume 2014, Article ID 836126, 9 pages
http://dx.doi.org/10.1155/2014/836126
Research Article

Proline Based Chiral Ionic Liquids for Enantioselective Michael Reaction

1Department of Applied Chemistry, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192, Japan
2Department of Biotechnology and Chemistry, Faculty of Engineering, Kinki University, 1 Takaya Umenobe, Higashihiroshima 739-2116, Japan

Received 29 August 2014; Revised 9 November 2014; Accepted 9 November 2014; Published 20 November 2014

Academic Editor: Kazuaki Ishihara

Copyright © 2014 Kaoru Nobuoka et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Chiral ionic liquids, starting from (S)-proline, have been prepared and evaluated the ability of a chiral catalyst. In Michael reaction of trans-β-nitrostyrene and cyclohexanone, all the reactions were carried out under homogeneous conditions without any solvent except for excess cyclohexanone. The chiral ionic liquid catalyst with the positive charge delocalized bulky pyrrolidinium cation shows excellent yields (up to 92%), diastereoselectivities (syn/anti = 96/4), and enantioselectivities (up to 95% ee) and could be reused at least three times without any loss of its catalytic activity. Such results demonstrated a promising new approach for green and economic chiral synthesis by using the chiral ionic liquids as a chiral catalyst and a chiral medium.