Visible-Light-Induced Regioselective C–H Sulfenylation of Pyrazolo[1,5-<i>a</i>]pyrimidines via Cross-Dehydrogenative Coupling
Suvam Paul, Sourav Das, Tathagata Choudhuri, Papiya Sikdar, Avik Kumar Bagdi
Abstract
A visible-light-induced cross-dehydrogenative methodology has been developed for the regioselective sulfenylation of pyrazolo[1,5- a ]pyrimidine derivatives. Rose bengal, blue LEDs, KI, K 2 S 2 O 8, and DMSO are all essential for this photocatalytic transformation. The protocol is applicable for the synthesis of a library of 3-(aryl/heteroaryl thio)pyrazolo[1,5- a ]pyrimidine derivatives with broad functionalities. The selectivity and scalability of the methodology have been also demonstrated. Moreover, the efficiency of this strategy for sulfenylation of pyrazoles, indole, imidazoheterocycles, and 4-hydroxy coumarin has been proven. The mechanistic investigation revealed the radical-based mechanism and formation of diaryl disulfide as a key intermediate for this cross-dehydrogenative coupling reaction.