Arylselenylations of methylbenzenes, methoxybenzenes and thiophene were smoothly achieved with selenenium ions generated by comproportionation of 1: 1 mixtures of p- toluenesulfonic acid salts of seleninic acids and the corresponding diselenides. A series of p- toluenesulfonic salts of seleninic acids were prepared by hydrogen peroxide oxidation of the corresponding diselenides in the presence of p-toluenesulfonic acid. Novel 2-( ...