Zinc Complexes of beta-Ketoiminato Ligands as Efficient Catalysts for the Synthesis of alpha-Amino Nitriles via Strecker Reaction

We report the synthesis of alpha-aminonitriles by one-pot coupling reaction of aldehyde, amines and trimethylsilyl cyanide (TMSCN) using beta-ketoiminato zinc complexes as a pre-catalyst in very good yield under mild reaction condition. Homoleptic zinc complex [{kappa(2)-(2,4,6-Me3C6H2NC(Me)=CHC(Me)=O)}(2)Zn] (1 a) was synthesized by the treatment of protic ligand [(2,4,6-Me3C6H2NHC(Me)=CHC(Me)=O)] ((LH)-H-1) with potassium hydride and anhydrous zinc diiodide in 2 : 2 : 1 molar ratio in THF. Analogous reactions using [(2,6-(Pr2C6H3NHC)-Pr-i(Me)=CHC(Me)=O)] ((LH)-H-2) and [(Ph2CHNHC(Me)=CHC(Me)=O)] ((LH)-H-3) as protic ligands, dinuclear zinc complexes [{kappa(3)-(2,6-(Pr2C6H3NC)-Pr-i(Me)=CHC(Me)=O)}ZnI](2)(1 b) and [Zn(Ph2CHNHC-(Me)=CHC(Me)=O)ZnI2] (1 c) were obtained in good yield. Molecular structures of ligandsL(1)H,(LH)-H-3, and zinc complexes1 a,1 b, and1 cwere established by single-crystal x-ray diffraction analysis. Dinuclear zinc complexes1 b, and1 cexhibited high transformation, greater selectivity and broad substrate scope for the synthesis of alpha-aminonitrile under mild condition. A most plausible mechanism for synthesis alpha-aminonitrile is proposed based on several controlled reactions.