Generation of thionitrosoarenes (ArNS) from N-(arylaminothio)phthalimides and in situ trapping with alkenes and conjugated dienes

A series of N-(arylaminothio)phthalimide derivatives (7a–h) has been prepared by reaction of phthalimidesulphenyl chloride with the trimethylsilyl derivative of the appropriate arylamine. On treatment with triethylamine at room temperature, compounds (7) fragment to yield transient thionitroso species (8). Derivatives (8a–h) have been trapped in good yield as their Diels–Alder adducts [e.g. N-aryl-1,2-thiazine derivatives (9) and (10)] with the following conjugated dienes: butadiene, 2,3-dimethylbutadiene, 1,4-diphenylbutadiene, (E,E)- and (E,Z)-hexa-2,4-diene, 1,1′-bicyclopentenyl (25) and 1,1′-bicyclohexenyl (26). The stereochemistry of the diene is retained in the adducts (19)–(24). Thionitrosoarene derivatives (8) also afford sulphenamide derivatives, e.g.(11) and (12)–(16), by ene addition to dimethylbutadiene, isobutene, and α-methylstyrene. N-Aryliminosulphur dichlorides (34) react with 2,3-dimethylbutadiene to yield 1,2-thiazine and sulphenamide products, probably by way of thionitrosoarene intermediates.