Highly Porous Cross-Linked Polymers for Catalytic Asymmetric Diethylzinc Addition to Aldehydes

Abstract

A series of five chiral cross-linked polymers (CCPs) based on the 1,1′-binaphthyl building blocks have been synthesized via the trimerization reaction of terminal alkyne groups, catalyzed by octacarbonyldicobalt complex (Co2(CO)8). The CCPs were highly porous, with surface areas of 689 to 974 m2/g and pore volumes of 0.87 to 1.23 cm3/g. The CCPs were insoluble in all solvents tested, including concentrated hydrochloric acid. The CCPs containing chiral dihydroxy functionalities were treated with Ti(OiPr)4 to generate chiral Lewis acid catalysts for the asymmetric diethylzinc addition to aldehydes. The enantioselectivity of these reactions is modest to good (55 to 81 e.e.%), but the CCPs could be readily recycled and reused for the asymmetric diethylzinc addition reactions for up to 10 times without loss of conversion or enantioselectivity.