New method for the synthesis of pyrromethanes

Coupling reaction of 2-mercaptobenzothiazolylmethylpyrrole with α-free pyrrole in the presence of silver(I) triflate proceeds smoothly at room temperature to give a pyrromethane in excellent yield. The azafulvenium ion, an active form that reacts with α-free pyrrole, also reacts with pyrromethane rapidly under similar neutral conditions to afford an equilibrated mixture of pyrromethanes in good yield.