Stereoselective titanium-mediated syn-aldol reaction from a lactate-derived chiral ethyl ketone

摘要

Stereoselectivity of the titanium-mediated aldol process based on (S)-2-benzyloxy-3-pentanone,1,is dramatically modified by the presence of a Lewis acid.Among the Lewis acids surveyed,TiCl_4 has given access to the corresponding 2A-anti-4,5-syn aldol adducts with the highest diastereomeric ratios.The excellent stereocontrol exerted by the aforementioned ketone has been demonstrated in double asymmetric reactions involving chiral alpha-methyl-beta-OTBDPS aldehydes.