Visible-Light-Driven Organophotocatalyzed Mono-, Di-, and Tri-C(sp)-H Alkylation of Phosphoramides.

A photocatalytic metal-free, visible-light-driven, highly atom-economic, direct multiple α-C(sp)-H alkylation of phosphoramides and thiophosphoramides is demonstrated under environmentally benign conditions. Economically viable and commercially available Eosin-Y is used as an HAT photocatalyst for mono-α-C(sp)-H alkylation of phosphoramide derivatives. Remarkably, di- and tri-C(sp)-H alkylation of phosphoramides and thiophosphoramides using an acridinium photocatalyst is reported with good yield and selectivity. Mechanistic studies reveal that monoalkylation of phosphoramides by Eosin-Y follows the HAT mechanism, whereas di- and tri-C(sp)-H alkylation by the acridinium photocatalyst follows the SET mechanism.