Chiral alkylzinc halide

The enantioselective addition of organometallics to aldehydes is a useful approach to optically active secondary alcohols. Diorganozinc reagents add with excellent enantioselectivity to aldehydes in the presence of a chiral catalyst such as 1,2- or 1,3-amino alcohols (see equation 14 and Table 2). In most cases, diethylzinc has been used, but the reaction could be extended to some other dialkylzinc reagents and to divinylzinc. Alkylzinc halides afford secondary alcohols with a substantially lower enantiomeric excess. Many aldehydes are good substrates, "- but the best results are usually obtained with aromatic aldehydes. ... 

Benzylic acetates are unreactive toward organozinc compounds. However, various ferrocenyl acetates, such as 236 react with alkylzinc halides in the presence of BF3 OEtj with retention of configuration leading to the chiral ferrocenyl derivatives like 237 (Scheme 7.68) [159]. 

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