Oil-soluble N,N-diarylammonium pyrosulfates as nonsurfactant-type catalysts for the dehydrative ester condensation under aqueous conditions are described. Preheat treatment of dibasic sulfuric acid with bulky N,N-diarylamines generates water-tolerant salts of pyrosulfuric acid as active catalyst species. The present catalysts in water can also widely be applied to unusual selective esterifications and dehydrative glycosylation.
Reverse micelle-type N,N-diarylammonium pyrosulfate (3-5 mol %) efficiently catalyzes the hydrolysis of esters (up to 100 mmol scale) under organic solvent-free conditions. The present method is successfully applied to the hydrolysis of various esters without the decomposition of the base-sensitive moieties and without any loss of optical purity for α-heterosubstituted carboxylic acids.
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