In situ phosphonium-containing Lewis base-catalyzed 1,6-cyanation reaction: facile way to α-diaryl and α-triaryl acetonitriles

Herein, we presente a phosphonium-containing catalyst generated in situ from phosphine and tert-butyl acrylate serves as an unusual Lewis base catalyst, and its successful application in promoting remote 1,6-cyanation reaction of p-QMs and fushones by employing TMSCN as cyanide source. A diverse range of α-diaryl and α-triaryl acetonitriles were obtained in high yields under mild reaction conditions with low catalyst loading (5 mol%). The practicality and utility of this protocol were demonstrated by the gram-scale preparation and facile elaborations of product. Mechanistic investigation including in situ NMR analysis and ESI-MS techniques have sucessfully characterized the real active zwitterionic phosphonium intermediate, which was the real active catalyst.