Regiochemistry of nucleophilic substitution of 4-phenylsulfonyl tetrafluoropyridine with unequal bidentate nucleophiles

The regiochemistry of nucleophilic substitution of 4-phenylsulfonyl tetrafluoropyridine with unequal bidentate nucleophiles was investigated. The first nucleophilic substitution occurs at the 2-position of the pyridine ring by nitrogen nucleophile site (secondary or primary amine) followed by intermolecular ring closure at the geometrically accessible 3-position of the pyridine ring (by S, O and N nucleophiles). From this investigation, difluorinated tetrahydropyrido[3,4-b][1,4]oxazine, thiazine and pyrazine scaffolds were synthesized very readily by a one-pot annelation reaction of 4-phenylsulfonyl tetrafluoropyridine with appropriate unequal bidentate nucleophiles.