Various alcohols and phenols, amines, thiols and thiophenols can be transformed easily to the corresponding acetate derivatives, on treating with two equivalent amount of acetic anhydride in the presence of 5 mol% bromodimethylsulfonium bromide pre-catalyst at room temperature in good yields. In addition, various aldehydes can also be converted to the corresponding gem-diacetates in good yields by employing 10 mol% of the same pre-catalyst using four equivalent amount of acetic anhydride. Some of the important features are: good yields, mild reaction conditions, no-aqueous work-up and chromatographic separation for a large-scale reaction, compatible with the substrates having other protecting groups and applicable to the carbohydrates and nucleosides. Interestingly, neither alkyl bromide formation from the corresponding alcohol nor bromination of the substrates took place under the experimental conditions. (c) 2005 Published by Elsevier B.V.