The synthesis of dendritic BINOL ligands and their applications in the enantioselective Lewis acid catalyzed addition of diethylzinc to aldehydes

摘要

Novel dendritic chiral BINOL ligands have been synthesized through coupling of MOM-protected 3,3′-dihydroxy-methyl- binaphthol with Fréchet-type polyether benzyl bromide dendrons followed by deprotection of the MOM groups using TsOH. These dendritic chiral BINOL ligands were found to be effective in the enantioselective addition of diethylzinc to benzaldehyde both in the presence and absence of Ti(O-iso-Pr)4. The enantioselectivity decreased with increasing generation in both cases. In the latter case, the dendritic chiral BINOL ligands showed much higher catalytic activity and enantioselectivity than BINOL.