Reaction of prop-2-ene-1-sulphonyl chloride with enamines: vinylthietan 1,1-dioxides and allylsulphonyl enamines as precursors of thiopyran 1,1-dioxides

Abstract

The reaction of prop-2-ene-1-sulphonyl chloride with enamines afforded 3-amino-2-vinylthietan 1,1-dioxides and/or allyl aminovinyl sulphones: no 1,4-cycloadducts were detected. Both the products were converted in the presence of base into 3-amino-3,4-dihydro-2H-thiopyran 1,1-dioxides, whose hydrochlorides underwent deamination to the corresponding thiopyran 1,1-dioxides. The intermediacy of the sulphones in the rearrangement of the vinylthietans to the thiopyrans is suggested; also it is suggested that the cyclisation of the sulphones proceeds through an allylsulphonyl carbanion.