3
Scheme 2. Reaction of N-phenylbenzamidine with pentafluoropyridine 29
Scheme 3. Proposed explanation for the formation of 7b
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Conclusion
In conclusion, we have demonstrated the efficient syntheses
of substituted imidazopyridines from the reaction of 4-
phenylsulfonyl tetrafluoropyridine with N-aryl amidines. In
contrast with 4-phenylsulfonyl tetrafluoropyridine, the reaction
of pentafluoropyridine with N-phenyl benzamidine gave N'-
(perfluoropyridin-4-yl)-N-phenylbenzimidamide and 2,3,5,6-
tetrafluoro-N-phenylpyridin-4-amine by a competing elimination
reaction.
Acknowledgment
The authors wish to thank Vali-e-Asr University of Rafsanjan
for partially funding this work.
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tetrafluoropyridine (1 mmol) and N-aryl amidine (2 mmol) in the
presence of NaHCO3 (4 mmol) in CH3CN (10 mL) was stirred at room
temperature for 7 days. The reaction mixture was poured into water (10
mL) and extracted with CHCl3 (3⨯10 mL), dried (MgSO4), and the
solvent evaporated. The crude product was purified by preparative TLC
(n-hexane/EtOAc). Procedure for the reaction of N-phenyl
benzamidine with pentafluoropyridine: Pentafluoropyridine (1 mmol),
N-phenyl benzamidine (2 mmol), NaHCO3 (4 mmol), and CH3CN (10
mL) were heated at reflux for 5 days. The reaction mixture was poured
into water (10 mL) and extracted with CHCl3 (3⨯10 mL), dried
(MgSO4), and the solvent evaporated. Purification by preparative TLC
(n-hexane/EtOAc, 2:1) gave products 7a and 7b.
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Highlights
Reaction of pentafluoropyridine with N-
phenylbenzamidine
Reaction of 4-phenylsulphonyl
tetrafluoropyridine with various N-arylamidines.
Synthesis of fluoro imidazopyridine systems.