Structure influence of chiral 1,1′-biscarboline-N,N′-dioxide on the enantioselective allylation of aldehydes with allyltrichlorosilanes

A series of new axially chiral 1,1′-biscarboline-N,N′-dioxide Lewis base organocatalysts were examined in the asymmetric allylation of aldehydes with allyltrichlorosilane. The chiral catalysts (R)-1a-e bearing ester groups in 3,3′ position provided good yields of the homoallyl alcohols with excellent enantioselectivities up to 99% for a broad substrate scope that covers aliphatic, aromatic, heteroaromatic, and α,β-unsaturated aldehydes. Solvent effects on the conversion and enantioselectivity were elucidated, and CH2Cl2 proved to be the optimal solvent for the reactions. In addition, the allylation with crotyltrichlorosilane was explored and the result showed that anti-isomer was favored from (E)-crotyltrichlorosilane with complete diastereoselectivity.