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 %.