Reaction of Aromatic N-Oxides with Dipolarophiles. IV. Factors affecting the 1,3-Cycloaddition of Pyridine 1-Oxide with Phenyl Isocyanates

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Pyridine 1-oxide was subjected to 1,3-dipolar cycloaddition with phenyl isocyanates having an ortho, meta or para substituent group. The reaction conducted at 90℃ in dimethylformamide gave the 2,3-dihydropyridine-form cycloadduct, although the reaction of pyridine 1-oxide with phenyl isocyanate directly affords 2-anilinopyridine. An increase of the reaction time led to increases in the yields of 2-anilinopyridine and 1-phenyl-carbamoyl-2-phenylimino-1,2-dihydropyridine, while the yield of the cycloadduct tended to decrease. The reaction at 150℃ resulted in an increased yield of 2-anilinopyridine. The reactions of 2-anilinopyridine and 5-methyl-2-anilinopyridine with phenyl isocyanate at room temperature afforded the corresponding 1-phenylcarbamoyl-2-phenylimino-1,2-dihydropyridines, whereas the reactions of 3-methyl- and 3,5-dimethyl-2-anilinopyridines with phenyl isocyanate at 90℃ afforded 2-(N-phenylcarbamoylanilino) pyridine derivatives.
社団法人日本薬学会の論文
1981-12-25