K. Ishihara et al., CATALYTIC ASYMMETRIC ALLYLATION USING A CHIRAL (ACYLOXY)BORANE COMPLEX AS A VERSATILE LEWIS-ACID CATALYST, Journal of the American Chemical Society, 115(24), 1993, pp. 11490-11495
In the presence of 20 mol % of a chiral (acyloxy)borane (CAB) complex
prepared from (2R,3R)-2-O-(2,6-diisopropoxybenzoyl)tartaric acid and b
orane-tetrahydrofuran, various allyltrimethylsilanes react with achira
l aldehydes to afford the corresponding homoallylic alcohols in good y
ields with high diastereo- and enantioselectivities. Furthermore, the
reactivity of allylation can be improved without reducing the enantios
elelctivity by using 10-20 mol % of the CAB complex prepared from 3,5-
bis(trifluoromethyl)phenylboronic acid and chiral tartaric acid deriva
tive. The observed selectivities and re-face attack of nucleophiles on
the carbonyl carbons of aldehydes imply that the extended transition-
state model is applicable.