Oxazole phenyl-, nitration

Oxazole, 2-dimethylamino-4-phenyl-nitration, 6, 190 Oxazole, 2,5-diphenyl-irradiation, 6, 189 nitration, 6, 190 oxidation, 6, 187 reduction, 6, 194 synthesis, 6, 222 Oxazole, 4,5-diphenyl-mercuration, 6, 190 2-substituted... 

Methyl-3-phenylisoxazole is nitrated as a conjugate acid at the meta position but as the free base at the para position of the phenyl group (79AHC(25)147). Phenyl groups attached to oxazole rings are nitrated or sulfonated in the para position, with relative reactivities of the phenyl groups in the order... 

Sec. II.B] NITRATION OF PHENYL-SUBSTITUTED HETEROCYCLES 239 5. Oxazoles and Isoxazoles... 

Attempts to carry out substitution reactions on oxazoles in acid media, such as nitration with nitric and sulfuric acids or chlorosulfonation, fail because the highly electron-deficient oxazolium cation is involved. Phenyloxazoles are nitrated at the para positions of the phenyl groups 2,5-diphenyloxazole affords 5-(4-nitrophenyl)-2-phenyloxazole, as expected. Nitrooxazoles are now available by the action of dinitrogen tetroxide on the corresponding iodo compounds (81JHC885). Benzoxazoles are nitrated at the benzene ring thus 2-methyl-benzoxazole gives a mixture of 5- and 6-nitro derivatives. 

Nitration of 2-methylbenzoxazole yields a 4 1 mixture of 6- and 5-nitro derivatives (cf. 2). Phenyl groups attached to oxazole at C(2), C(4), or C(5) are nitrated in the para-positions and the resulting (nitrophenyl)oxazoles can be reduced chemically to the corresponding amino compounds. 

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