C-Centered optically active organosilanes. 2. Application to enantioselective allylation of carbonyl compounds

The title allylsilanes, e.g., I, react with carbonyl compds. in the presence of Lewis acids to give the corresponding homoallyl alcs. with ee varying from 21 to 56%. E.g., I reacted with butanal in the presence of TiCl4 to give CH3CH2CH2CHOHCH2CH:CH2 in 58% yield with 46% ee. The role of the Lewis acid is crucial for a correct development of the reactions; different procedures are tested and the results compared.