Singlet Oxygen Driven Stereoselective Iodothiocyanation and Iodoselenocyanation of Alkynes

Abstract

We present here a low-energy visible light-induced metal-free C-I, C-S, and C-Se cross coupling reactions for the formation of iodo-vinyl-thiocyanates (IVTs) and iodo-vinyl-selenocyanates (IVSs) using alkynes, iodine and ammonium thiocyanate (NH4SCN)/ potassium selenocyanate (KSeCN) in the presence of oxygen at room temperature. Herein, iodine, molecular oxygen, and NH4SCN on photo-irradiation synergistically generate iodine radical, singlet oxygen (1O2), and •SCN /•SeCN radicals and selectively react with alkyne to form stereoselective E-configured IVTs and IVSs. Significantly, iodine plays an important role as I2 acts as a photocatalyst, and upon photo-irradiation, generate iodine radicals via homolytic cleavage of I2, singlet oxygen via energy transfer (ET), and thiocyanate/selenocyanate radicals via single electron transfer (SET) process. Moreover, Green chemistry metrics and Eco-scale evaluations highlight that the current stereoselective oxidative C-I, C-S, and C-Se coupling protocol aligns well with sustainable principles, establishing it as a viable and environmentally benign approach to organic synthesis.