Catalytic asymmetric cyanation reactions of aldehydes and ketones provide efficient routes for the synthesis of optically active cyanohydrins, which are versatile synthons for the preparation of natural products and chemical pharmaceuticals. This review aims to provide a summary of recent achievements concerning catalytic enantioselective cyanation reactions of aldehydes and ketones employed in the total syntheses of various natural products, drugs, and pharmaceutically active compounds.magnified image

The first highly enantioselective construction of chiral cyclopropa[c]coumarins was described. Using commercially available (bis)cinchona alkaloid (DHQ) 2 PYR as the chiral Lewis base catalyst, together with Cs 2 CO 3 as the achiral base, the reaction of a series of coumarin-3-carboxylate and 3-benzoyl coumarins with tert-butyl 2-bromoacetate could give rise to the corresponding cyclopropa[c]coumarins bearing three continuous chiral stereocenters in 83−93% ee and 90−97% ee, respectively. The reaction is proposed to proceed via an in situ generated ammonium ylide intermediate.

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Coumarins and 2H-pyran derivatives are among the most commonly found structural units in natural products. Therefore, the introduction of 2H-pyran moiety into the coumarin structural unit, i.e., dihydrocoumarin-fused dihydropyranones, is a potentially successful route for the identification of novel bioactive structures, and the synthesis of these structures has attracted continuing research interest. Herein, a chiral tertiary amine catalyzed [4 + 2] cyclization of 3-aroylcoumarines with benzyl 2,3-butadienoate was reported. In the presence of Kumar’s 6’-(4-biphenyl)-β-iso-cinchonine, the desired dihydrocoumarin-fused dihydropyranone products could be obtained in up to 97% yield and 90% ee values.

Category Organo-and BiocatalysisKey words asymmetric hydrosilylation chiral amines chiral sulfinamides ketimines trichlorosilane D . P E I , Z .