text: The Curtin–Hammett principle has been invoked to explain regioselectivity in the acylation of 1,2-diols. Ordinarily, the less-hindered site of an asymmetric 1,2-diol would experience more rapid esterification due to reduced steric hindrance between the diol and the acylating reagent. Developing a selective esterification of the most substituted hydroxyl group is a useful transformation in synthetic organic chemistry, particularly in the synthesis of carbohydrates and other polyhydroxylated compounds. Stannylene acetals have been used to efficiently achieve this transformation.
  The asymmetric diol is first treated with a tin reagent to produce the dibutylstannylene acetal. This compound is then treated with one equivalent of acyl chloride to produce the stannyl monoester. Two isomers of the stannyl ester are accessible, and can undergo rapid interconversion through a tetrahedral intermediate. Initially, the less stable isomer predominates, as it is formed more quickly from the stannyl acetal. However, allowing the two isomers to equilibrate results in an excess of the more stable primary alkoxy stannane in solution. The reaction is then quenched irreversibly, with the less hindered primary alkoxy stannane reacting more rapidly. This results in selective production of the more-substituted monoester. This is a Curtin–Hammett scenario in which the more stable isomer also reacts more rapidly.