Montmorillonite clay catalyzed tosylation of alcohols and selective monotosylation of diols with p-toluenesulfonic acid: an enviro-economic route

Abstract

An enviro-economic route for tosylation of alcohols and selective monotosylation of diols in good yield directly using p-toluenesulfonic acid together with metal-exchanged montmorillonite instead of p-toluenesulfonyl chloride or p-toluenesulfonic anhydride is described. The Fe³⁺-montmorillonite clay is the most effective catalyst among metal-exchanged montmorillonites for such tosylation reactions. The activity follows the sequence Fe³⁺>Zn²⁺>Cu²⁺>Al³⁺-montmorillonite >K10 montmorillonite. Regioselective tosylation of diols to monotosylated derivatives is achieved with high purity. In diols having both primary and secondary hydroxy groups, tosylation occurred only at the primary hydroxy group. The solid catalyst displayed consistent activity for several cycles as exemplified in tosylation of cyclohexanol.