An efficient two-step method for the differential functionalization of 1, 2-and 1, 3-diols, involving regioselective cleavage of five-and six-membered cyclic formals with acetyl chloride followed by conversion of the resulting chloromethyl ether acetate 1 to an alkoxymethyl ether acetate (21, has been developed. When applied to unsymmetrically substituted cyclic formals, the differential functionalization sequence is highly selective ...