Chiral Metal–Organic Framework as a Platform for Cooperative Catalysis in Asymmetric Cyanosilylation of Aldehydes

In this work, we demonstrate cooperative asymmetric catalysis by a metal–organic framework (MOF) as exemplified in the context of catalyzing cyanation of aldehydes with a VO(salen)-MOF, which after oxidation affords remarkably increased stereoselectivity (up to >99% ee) compared to the homogeneous VO(salen) counterpart as a result of the pairs of VO(salen) units in close proximity within its open channels. The cooperative asymmetric catalysis has been evidenced by the significantly decreased stereoselectivity and activity when one VO(salen) in such pairs of VO(salen) units is replaced with one Cu(salen), which results in blocking the VO–VO synergistic pathway while prompting unimolecular activation of substrates. The heterogeneous nature of VO(salen)-MOF has been verified by the fact that it can be easily recycled and reused without significant loss of catalytic activity and enantioselectivity, and its practical utility as asymmetric cyanation catalysist has been illustrated in the gram-scale synthesis of the antiviral natural products (R)- and (S)-enantiomers of tembamide. Our work therefore advances chiral MOF as an attractive platform for cooperative asymmetric catalysis in a variety of syntheses.