3-Chloro-4-fluorothiophene-1,1-dioxide. A new synthetically useful fluorodiene

Article abstract of DOI:10.1016/S0022-1139(98)00109-2

Simple, three step synthesis of a new fluorine containing diene, 3-chloro-4-fluorothiophene-1,1 -dioxide (4), from commercially available 3-sulpholene (1) has been developed. The synthetic value of compound 4 as a Diels - Alder diene has been demonstrated by its reactions with various type of dienophiles: acetylenes, alkenes, furans, quinone and anthracene. The reactions proceed with high regioselectivity to give good yields of 3-fluoro-4-chloro substituted aromatics or cyclic chlorofluorodienes. In reactions with alkenes, immediate aromatisation often occurs. In some instances, when reacted with a diene, compound 4 behaves as a dienophile.