Direct synthesis of 1,3-dithiolanes from terminal alkynes via visible light photoredox catalysis

A visible light-mediated, metal-free, regioselective dihydrothionation of terminal aromatic as well as heteroaromatic alkynes has been achieved using Eosin Y as a photoredox catalyst at room temperature. The protocol gives direct access to different 1,3-dithiolanes under neutral and mild reaction conditions without the use of any base or additives. The electron-donating, electron-withdrawing and electron-deactivating groups tolerated the photocatalytic reaction conditions. The control experiments, cyclic voltammetry, and Stern-Volmer experiment were carried out to gain an insight into the mechanistic pathway. The protocol proved to be scalable at the gram level and also for practicality the deprotection of 1,3-dithiolanes has been demonstrated. The method uses clean energy under sustainable conditions.

Automated summary

This study successfully achieved the metal-free, regioselective dihydrothionation of terminal aromatic and heteroaromatic alkynes using Eosin Y as a photoredox catalyst. The reaction provides a direct and mild approach to different 1,3-dithiolanes without the need for bases or additives. The reaction conditions tolerate various electron-donating, electron-withdrawing, and electron-deactivating groups. The mechanism was investigated using control experiments and cyclic voltammetry, and the scalability of the method was demonstrated. The use of clean energy under sustainable conditions is a highlight of this protocol.