The chemistry of acyl- and sulphonyl-thionitroso compounds

Abstract

Thiophene S,N-ylides undergo cycloadditions with nucleophilic alkenes to give [4 + 2] adducts with concomitant extrusion of acylthionitroso compounds. These new and highly reactive species may be trapped by dienes (to give thiazines by [4 + 2]cycloaddition) or by enes (to give acylthiohydroxylamines by ene reaction). With suitable dienes such as isoprene and dimethylbutadiene, the ene reaction competes with the diene addition. In the absence of a trap, ethyl thionitrosoformate in aromatic solvents yields bis(ethoxycarbonyl amino) sulphide, while with cyclopentadiene a 2:1 adduct, a rare example of a 1,3,2,4-dithiadiazine, is formed. Thiophene is shown to yield a transient S,N-ylide on treatment with ethoxycarbonylnitrene.