Zinc Complexes of β‐Ketoiminato Ligands as Efficient Catalysts for the Synthesis of α‐Amino Nitriles via Strecker Reaction

Abstract

AbstractWe report the synthesis of α‐aminonitriles by one‐pot coupling reaction of aldehyde, amines and trimethylsilyl cyanide (TMSCN) using β‐ketoiminato zinc complexes as a pre‐catalyst in very good yield under mild reaction condition. Homoleptic zinc complex [{κ2‐(2,4,6‐Me3C6H2NC(Me)=CHC(Me)=O)}2Zn] (1 a) was synthesized by the treatment of protic ligand [(2,4,6‐Me3C6H2NHC(Me)=CHC(Me)=O)] (L1H) with potassium hydride and anhydrous zinc diiodide in 2 : 2 : 1 molar ratio in THF. Analogous reactions using [(2,6‐iPr2C6H3NHC(Me)=CHC(Me)=O)] (L2H) and [(Ph2CHNHC(Me)=CHC(Me)=O)] (L3H) as protic ligands, dinuclear zinc complexes [{κ3‐(2,6‐iPr2C6H3NC(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 ligands L1H, L3H, and zinc complexes 1 a, 1 b, and 1 c were established by single‐crystal x‐ray diffraction analysis. Dinuclear zinc complexes 1 b, and 1 c exhibited high transformation, greater selectivity and broad substrate scope for the synthesis of α‐aminonitrile under mild condition. A most plausible mechanism for synthesis α‐aminonitrile is proposed based on several controlled reactions.