Highly efficient and stereoselective access to (Z)-α,β-difluoroallyl alcohols and (Z)-α-fluoro-α,β-unsaturated aldehydes based on the reaction of 2,3,3-trifluoro-1-propenyl p-chlorobenzenesulfonate with Grignard reagents

2,3,3-Trifluoro-1-propenyl p-chlorobenzenesulfonate (1), readily available from 2,2,3,3-tetrafluoropropanol, reacted smoothly with various Grignard reagents at 50 degrees C to afford the corresponding (Z)-alpha,beta-difluoroallyl alcohols 2 in moderate to excellent yields. These alcohols were smoothly hydrolyzed in the presence of a catalytic amount of mentmorillonite K10 (Clay) to provide (Z)-alpha-fluoro-alpha,beta-unsaturated aldehydes 3 in good yields. (C) 1998 Elsevier Science Ltd. All rights reserved.