Heteropoly Acids as Heterogeneous Catalysts for Thioacetalization and Transthioacetalization Reactions

Abstract

Heteropoly acids are effective solid catalysts for the thioacetalization of carbonyl compounds. Tungstophosphoric acid (H₃PW₁₂O₄₀), was found to be an effective and a highly selective catalyst for the thioacetalization of aldehydes, ketones and for the transthioacetalization of acetals, acylals and O,S-acetals which proceeded in excellent yields in the absence of solvent. The catalyst has also been successfully applied to the chemoselective conversion of α- or β-diketones and a β-keto ester into the corresponding dithioacetals. Sterically hindered carbonyl compounds such as camphor and benzophenone were also converted to their corresponding thioacetals in refluxing petroleum ether in 89-94% yields. Surprisingly, anthrone was reduced to anthracene in 91% yield.

Key words

carbonyl compounds - tungstophosphoric acid - heteropoly acids - thioacetalizations - transthioacetalizations

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