3,5-Dialkyltetrahydro-4H-thiopyran-4-ones under the conditions of Mannich reaction

Thiomethylation of pentan-3-one, 5-methylhexan-3-one, and heptan-4-one with a mixture of formaldehyde and sodium sulfide gave the respective 3,5-dialkyltetrahydro-4H-thiopyran-4-ones, while 3,5-dihydroxymethyl- or 3,5-dialkyl-5-hydroxymethyltetrahydro-4Hthiopyran-4-ols were formed in the presence of primary amines. The oxidation of 3,5-dimethyltetrahydro-4H-thiopyran-4-one with an equivalent amount of hydrogen peroxide in tetrahydrofuran and chloroform led to the sulfoxide and sulfone, respectively, while aminomethylation with a mixture of formaldehyde and methylamine, hexylamine, monoethanolamine, or hydrochlorides of methyl, ethyl, and 2-propyl esters of aminoacetic acid at рH 7–8 produced the respective 1,5-dimethyl-3-thia-7-azabicyclo[3.3.1]nonanes. An equilibrium between the chair and boat conformations in the thiopyranone ring was found in CDCl3 solutions of 7-(2-hydroxyethyl)-1,5-dimethyl-3-thia-7-azabicyclo[3.3.1]nonan-9-one at 50°С and DMSO-d 6 solutions of 1,5,7-trimethyl-3-thia-7-azabicyclo[3.3.1]nonan-9-one monoperchlorate at 20°С.