Novel synthesis of 4,4-difluoropyrido[4,3-b]indoles via intramolecular Heck reaction

Various difluoropyridoindoles were synthesized via a palladium-catalyzed intramolecular Heck reaction as a key step. Thus, ortho-bromoanilines and difluoropiperidinone were treated with (PPh3)2PdCl2 and base in pyridine to give the regioselective cyclized heterocycles in modest to satisfactory yields.