Asymmetric Aldol Additions: Use of titanium tetrachloride and (-)-sparteine for the soft enolization of N-acyl oxazolidinones, oxazolidinethiones, and …

…, BW King, EA Tabet, K Chaudhary

Index: Crimmins; King; Tabet; Chaudhary Journal of Organic Chemistry, 2001 , vol. 66, # 3 p. 894 - 902

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Citation Number: 391

Abstract

Asymmetric aldol additions using chlorotitanium enolates of N-acyloxazolidinone, oxazolidinethione, and thiazolidinethione propionates proceed with high diastereoselectivity for the Evans or non-Evans syn product depending on the nature and amount of the base used. With 1 equiv of titanium tetrachloride and 2 equiv of (-)-sparteine as the base or 1 equiv of (-)-sparteine and 1 equiv of N-methyl-2-pyrrolidinone, selectivities of 97: 3 to> 99: ...