Condensation of 3,5-Dialkyltetrahydro-4H-thiopyran-4-ones with Formaldehyde

Abstract— The reaction of 3,5-dimethyl- and 5-methyl-3-(2-propyl)tetrahydro-4H-thiopyran-4-ones with formaldehyde without or in the presence of 0.1–0.5 equiv. sodium hydroxide produces 3,5-dialkyl-3-(hydroxymethyl)tetrahydro-4H-thiopyran-4-ones. 3,5-Dimethyltetrahydro-4H-thiopyran-4-one converted into 3,5-bis(hydroxymethyl)tetrahydro-2H-thiopyran-4-ol when the amount of base to 1 equiv increase. Under similar conditions 5-methyl-3-(2-propyl)tetrahydro-4H-thiopyran-4-one form 3-hydroxymethyltetrahydro-2H-thiopyran-4-ol, which cyclization to 7-oxa-3-thiabicyclo[4.2.0]octane.