Hydroxyl group substitution, effect method

Monoacylation of diols.1 Monoacylation of unsymmetrical 1,2-, 1,3-, and 1,4-diols can be effected by acylation of the dibutylstannylene derivatives, followed by quenching with oxalic acid or ClSi(CH3)2C6H5. This process effects monoacylation of the more-substituted hydroxyl group, even a tertiary one. This method also is... 

Corey s double activation procedure (Method 2) does not use an external reagent to activate the functional group, but effects cyclization by heating a solution of the 2-pyridinethiol ester of a hydroxy acid for a prolonged period. Several pieces of evidence point to the intermediacy of 2 in this lactonization.10 If one accepts this intermediate, it follows that a hydroxy(2-pyridinethiolJ ester, heavily substituted near the reaction centers (i.e., near the hydroxyl and acyl groups), would encounter a high... 

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