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

• Published in: Asian journal of organic chemistry 2020-08, Vol.9 (8), p.1217-1224
• Main Authors: Das, Suman, Kumar, Ravi, Devadkar, Ajitrao, Panda, Tarun K.
• Format: Article
• Language: English
• Subjects: Aldehydes; Amines; carbonyl compounds; Catalysts; Chemical synthesis; Coordination compounds; Coupling (molecular); Ligands; Molecular structure; Nitriles; Organic chemistry; Potassium hydrides; Selectivity; Strecker reaction; Substrates; Zinc; Zinc compounds; α-amino nitrile; β-ketoiminato
• ISSN: 2193-5807; 2193-5815
• DOI: 10.1002/ajoc.202000278

We 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. ‘Zinc’ into it: Catalytic one‐pot reaction of aldehyde, amine, and TMSCN to synthesize α‐amino nitrile by using a new dinuclear zinc complex has been reported. The reaction demonstrated wide substrate scope and high yield of products.