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Catalytic enantioselective Strecker-type reactions of aldimines with tributyltin cyanide (Bu3SnCN) proceeded smoothly in the presence of a novel chiral zirconium catalyst. High levels of enantioselectivities in the synthesis of α-amino nitrile derivatives with wide substrate generality were obtained via these reactions. In addition, hydrogen cyanide (HCN) was successfully used instead of Bu3SnCN as the cyanide source. Catalytic asymmetric Strecker amino acid synthesis starting from achiral aldehydes, amines, and HCN using a chiral zirconium catalyst has also been achieved. The three-component asymmetric process reported here significantly improves upon the original Strecker reaction, and has advantages over previous reactions using unstable imines (Schiff bases) as starting materials. Moreover, high yields and enantioselectivities have been obtained even in the reactions using aliphatic aldehydes, and both enantiomers of various types of α-amino acid derivatives can be prepared. As demonstrations to show the utility of this reaction, efficient syntheses of homophenylalanine, leucine amide, and pipecolic acid derivatives have been performed. Finally, two novel binuclear zirconium complexes (3 and 4) are postulated to be active chiral catalysts in the reactions of aldimines with Bu3SnCN and the three-component reactions, respectively, and low loading levels of the chiral catalysts (1−2.5 mol %) have been accomplished in both cases.

Chiral dihydropyridone derivatives 3 are obtained in high yields and with good enantioselectivities by the title reaction of aldimines such as 1 with Danishefsky's diene 2. 6,6'-Dibromo-1,1'-binaphthol complexes with Group 4 metals serve as catalysts; zirconium proved to be especially effective.

Strecker reactions of aldimines with Bu SnCN in the presence of the novel chiral zirconium binuclear catalyst 1 provide α-aminonitriles in good yields and with high enantioselectivities. The reaction can be applied to a wide range of substrates. Since both enantiomers of the chiral sources are readily avaibable, both enantiomers of the α-aminonitriles are easily prepared according to this method. L=N-methylimidazole.

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