Selective monosulfonylation of internal 1,2-diols catalyzed by di-n-butyltin oxide

The reaction of internal 1,2-diols with catalytic n-Bu2SnO, p-TsCl (1.05 equiv.) and Et3N (1.1 equiv.) led to selective monotosylation. In the case of cyclic substrates, the cis-1,2-diol moiety appeared best suited for optimal results, supporting the intermediacy of a five-membered chelate.