Enantioselective addition of diethylzinc to benzaldehyde catalyzed by an organometallic Ti(IV) compound and a xylose derivative

a derivative of d-xylose, 1,2-o-isopropylidene-α-d-xylofuranose (1), with ti(oipr)4 was used as a chiral catalyst in the asymmetric alkylation of benzaldehyde with diethylzinc (et2zn) for the high-yield production (90% conversion) and moderate enantioselectivity (45% ee (s)) of 1-phenyl-1-propanol. optimum conditions (conversion and enantioselectivity) for the catalytic system formed by 1 and ti(iv) were 10.0 mol % of 1 and 1 equivalent of ti(iv) with respect to benzaldehyde in ch2cl2 as a solvent, at room temperature. in the asymmetric alkylation of benzaldehyde with et2zn compound 1 in substoichiometric amount with ti(oipr)4 forms a chiral catalyst of the ti(iv)-sugar type that ensures the good-yield conversion and the enantioselectivity of the reaction.