Visible-Light-Mediated Regioselective C3-H Selenylation of Pyrazolo[1,5- a ]pyrimidines Using Erythrosine B as Photocatalyst.

A visible-light-induced efficient methodology has been developed for the C-H selenylation of pyrazolo[1,5- a ]pyrimidine derivatives employing erythrosine B as the photocatalyst. This is the first report on the regioselective selenylation of pyrazolo[1,5- a ]pyrimidines. The efficiency of this methodology for the selenylation of different electron-rich heterocycles like pyrazole, indole, imidazo[1,2- a ]pyridine, imidazo[2,1- b ]thiazole, and 4-(phenylamino)-2 H -chromen-2-one has been also demonstrated. The exploration of erythrosine B as a photocatalyst with a simple and mild procedure, wide substrate scope, and practical applicability and the employment of eco-friendly energy, oxidant, and solvent are the attractive characteristics of this methodology.