CATALYTIC ENANTIOSELECTIVE ADDITION OF DIETHYLZINC TO (HETERO)AROMATIC ALDEHYDES

The asymmetric alkylation with diethylzinc of five heterocyclic aldehy des and benzaldehyde (for comparison) has been studied in the presence of two optically active amino alcohols: (S)-2-amino-1-butanol (AB) an d (1S,2R)-N,N-dibutylnorephedrine (DBNE), A number of chiral (hetero)a romatic secondary alcohols were synthesized in high yields (95-98%) wi th enantioselectivity up to 92% enantiomeric excess (ee) in the presen ce of DBNE catalyst, Optically active thienyl and 4-pyridyl derivative s were prepared for the first time by catalytic asymmetric alkylation, The influence of the amount of DBNE on the enantioselectivity was inv estigated, In contrast to benzaldehyde, 2-furan- and 2-thiophene-carba ldehydes, in the case of 3- and 4-pyridinecarbaldehydes the se values depend directly on the catalyst concentration. (C) 1998 John Wiley & S ons, Ltd.