Hydrostannation of Terminal Alkynes Catalyzed by Organozinc Compounds

Abstract: The use of two economically viable and environmentally benign nonprecious-metal organozinc complexes as catalysts for the hydrostannation of terminal alkynes has been reported. Commercially available ZnEt₂ and a laboratory-prepared β-diketiminate ethylzinc complex LZnEt [L = HC(CMeNAr)₂, Ar = 2,6-(i-Pr)₂C₆H₃] exhibit excellent catalytic efficiency in the hydrostannation of terminal alkynes with Bu₃SnH, showing a broad substrate scope across aromatic, aliphatic, and alicyclic derivatives. Notably, ZnEt₂ demonstrates slightly higher catalytic activity than LZnEt, whereas the sterically demanding complex LZnEt provides enhanced stereoselectivity, which is attributed to its greater steric hindrance. A plausible mechanism for the ZnEt₂-catalyzed stannylation of terminal alkynes is proposed based on key reaction intermediates characterized by NMR spectroscopy.