Chloroform → 5-Methyl-2H-thiopyran-1,1-dioxide

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Reaction Steps

5-Methyl-2H-thiopyran-1,1-dioxide is prepared in three steps from 3-methyl-3-sulfolene using the method of Gaoni, J. Org. Chem., 46 (1981) 4502. Thus, 3-methyl-3-sulfolene is first reacted with chloroform and aqueous sodium hydroxide in the presence of a quaternary ammonium salt to give the dichlorocarbene adduct. Partial dehalogenation with lithium aluminum hydride in tetrahydrofuran gives the chlorocyclopropane. Finally, base-catalyzed ring expansion with lithium diisopropylamide gives the desired thiopyran dioxide compound (see Scheme 1, above).

Provenance & Evidence