Development of Bronsted Acid-Metal Bifunctional Catalyst Based on Bisamidine Framework

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The rational design and development of a highly efficient catalyst for asymmetric catalytic reaction is of ongoing considerable interest in organic chemistry. Focusing on the steric and electronic properties of the bisamidine framework, two types of chiral catalysts were developed. The cationic zinc bisamidine complex acts as a Bronsted-Lewis combined acid to promote asymmetric Mukaiyama aldol reaction of α-ketoesters. The aldol products were obtained in good yields but with low enantioselectivities. Addition of the fluoroalcohol having suitable acidity and bulkiness led to dramatic increase in enatioselectivity. The multinuclear zinc bisamidinate catalyzed asymmetric alkylation of α-ketoesters to afford the products in high yields and enantioselectivities.