Practical and Safe Sulfonylation of 2-Alkynyl and 2-Alkenyl Alcohols Using the Combined Bases of a Catalytic Amount of Tertiary Amine and Potassium Carbonate

Several 2-alkynyl and 2-alkenyl alcohols were effectively sulfonylated with methanesulfonyl chloride or p-toluenesulfonyl chloride using the combined bases of a catalytic amount of tertiary amine and potassium carbonate. The reaction was conducted with reliable safety and while avoiding the disposal of wasted amines. The mesylation of 2-propyn-1-ol proceeded on a large scale (more than 20 kg) without a substantial production of explosive 3-chloro-1-propyne. The choice of the catalysts was important, and sterically unhindered tertiary amines, such as trimethylamine, N,N-dimethylbenzylamine, and triethylamine, were effective. Without these catalysts the reactions were significantly retarded. The reaction was so mild that it could be applied to complex and optically active 4-hydroxy-3-methyl-2-(2-propynyl)-2-cyclopenten-1-one, which is an important alcohol moiety of synthetic pyrethroids.