Thioketenes and Iminopropadienethiones RN=C=C=C=S from Isoxazolones

Abstract

Isoxazolones 6 undergo thermal elimination of propene and isopropylthiol to produce thioketenes 7 at 500–600°C under flash vacuum thermolysis conditions. At 700–900°C further fragmentation occurs to produce iminopropadienethiones, RNCCCS 8. In addition, 3-alkylisoxazolones 6d–e rearrange to cyanothioketenes 10d–e. Compounds 7, 8, and 10 were characterized by Ar matrix IR spectroscopy and comparison with density functional theory-calculated spectra. Thioketenes 7 reacted with amines to afford thioamides 11. Reaction of aryliminopropadienethiones 8 with amines caused cyclization to 2-aminoquinoline-4(1H)-thiones 16.