Synthesis 2008(21): 3361-3376  
DOI: 10.1055/s-0028-1083171
REVIEW
© Georg Thieme Verlag Stuttgart ˙ New York

New Approach for Complete Reversal of Enantioselectivity Using a Single Chiral Source

Takanori Tanaka, Masahiko Hayashi*
Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501, Japan
Fax: +81(78)8035688; e-Mail: mhayashi@kobe-u.ac.jp;
Further Information

Publication History

Received 7 April 2008
Publication Date:
16 October 2008 (online)

Abstract

Obtaining both enantiomers of a given compound in high enantiomeric excess is an attractive and important challenge, because it is often the case that each enantiomer exhibits different bioactivity. This review summarizes some approaches to realize complete reversal of enantioselectivity by changing various reaction conditions. Our new approach to achieve reversal of enantioselection in the enantioselective addition of diketene to aldehydes, affording optically active 5-hydroxy-3-keto esters in high optical yield using Schiff bases that contain an oxazoline moiety derived from l-serine, is also described.

1 Introduction

2 Reversal Based on the Nature of the Substituent

2.1 Control with Catalyst Substituent

2.2 Control with Substrate Substituent

3 Control with Central Metal

4 Reversal of Enantioselectivity by Changing Reaction Conditions

4.1 Control with Solvent

4.2 Control with Temperature

4.3 Control with Additives

4.4 Control with Other Factors

5 Recent Concepts for Reversal of Enantioselectivity

5.1 Asymmetric Addition of Readily Available Nucleophiles with Aldehydes

5.2 Enantioselectivity Reversal in Asymmetric Addition of Diketene with Aldehydes

6 Conclusions and Outlook

26

Recently, many cases of ligand acceleration effect have been reported in which chiral ligands accelerate reactivity.