Synthesis of monofluorinated indolizines and their derivatives by the 1,3-dipolar reaction of N-ylides with fluorinated vinyl tosylates

Monofluorinated indolizines , benzo[d]indolizines and 4H-pyrrolo[1,2-a]benzimidazoles were synthesized in moderate yields by 1,3-dipolar reaction between fluorinated vinyl tosylates and N-ylides of pyridinium, isoquinolinium and benzimidazolinium, generated in situ from their halides salts. When the same N-ylides were allowed to react with 2,3,3-trifluoro-1-propenyl tosylate , the unexpected product formylated indolizines and their derivatives were obtained. The reaction mechanism is also proposed.