A Two-Step Conversion of Carbonyl Compounds into Functionalized Five-and Six-Membered Ring Thioethers via Intramolecular Cycloaddition

Reaction of aldehydes or ketones with nitromethane in the presence of unsaturated thiols led directly to unsaturated nitro sulfides 7,12,14, or 19. These compounds were converted by intramolecular nitrile oxide—olefin cycloaddition to tetrahydrothiopheno[3,4-c]isoxazoles 9, 10, 13, and 20 or to homologous thiopyrans 15 and 16 in some cases with a fair degree of stereoselectivity. Reduction of 9 or 13 led to tetrahydrothiophenes possessing stereoselectively placed amino alcohol functions, while desulfurization provided open-chain keto alcohol 24.