Kinetically controlled regiospecific silylation of polyols via dibutylstannanediyl acetals

A general procedure is described whereby the tert-butyldimethylsilylation of unsymmetrical 1,2- and 1,3-diols via their dibutylstannanediyl derivatives occurs regiospecifically at the primary hydroxy group under neutral conditions; six-membered ring acetals (derived from 1,3-diols) are found to react in preference to five-membered ring acetals (derived from 1,2-diols), the reverse of stannanediyl-mediated acylation, tosylation and alkylation procedures, leading to kinetically controlled discrimination between the different primary hydroxy groups of polyol systems such as butane-1,2,4-triol and lactose.