Further improvements of the dibutyl tin oxide-catalyzed regioselective diol tosylation

In this Letter, we report that selective monotosylation of a 1,2-diol is possible using only 0.1 mol % of Bu2SnO. More interestingly, we found that the corresponding tin acetal 3b gave faster conversions and more reproducible reaction times. Moreover, the loading of this catalyst could be as low as 0.05–0.005 mol %.