Metal-free photocleavage of the C(non-acyl)-S bond of thioesters for regioselective pyridylthioesterification of styrenes

Transformation of thioesters via transition-metal-mediated C(acyl)-S bond cleavage is an emerging method to forge C-C and C-S bonds. Herein, we report the first activation of a stronger C(non-acyl)-S bond of thioesters for metal- and photoredox catalyst-free visible-light-mediated pyridylthioesterification of styrenes with excellent chemo- and regio-selectivity. This atom-economic protocol exhibits high functional group tolerance, is applicable to follow-up transformation of drug molecules, and is easy to set up for gram-scale reaction. Mechanistic studies revealed that this process is initiated by blue light irradiation of ternary electron donor-acceptor (EDA) complexes, formed by the aggregation of two substrates with HNEt2 as a traceless electron-donor.