Synthesis of 2-Fluorinated Pyrazolo[1,5-a]pyridines via Base- Mediated [3+2] Cycloaddition of N-Aminopyridinium Salts with gem-Difluorostyrenes

A method for the construction of 2-fluoropyrazolo[1,5- a ]pyridines through base-promoted [3+2] cycloaddition of N -aminopyridinium salts with gem -difluorostyrenes has been established.