Stereoselective titanium-mediated aldol reactions of (S)-2-tert-butyldimethylsilyloxy-3-pentanone
摘要:
Titanium-mediated aldol reactions based on (S)-2-tert-butyldimethylsilyloxy-3-pentanone, a lactate-derived chiral ketone, provide the corresponding 2,4-syn-4,5-syn adducts in high yields and diastereomeric ratios with a wide array of achiral and chiral aldehydes. Furthermore, spectroscopic studies of intermediates involved in the process have permitted to propose a mechanism that accounts for the experimental results. (c) 2006 Elsevier Ltd. All rights reserved.
[reaction: see text]Comprehensive analysis of the enolization of alpha-silyloxyketones by Chx2BCl/R3N has allowed us to design stereoselective Chx2BCl-mediated aldol processes that afford syn or anti aldol products and to disclose a hypothesis that accounts for the subtle effects that determine their enolization.