Oxazole 5- nitro-2-phenyl

Oxazol 5-(4-Nitro-phenyl)-2-oxo-2.3-dihydro- E15/2, 1258 (2-N3CO-oxiran/A)... 

Oxazol (5R)-5-Nitro-3-(4-nitro-phenyl)-4,5-dihydro- E16d, 243 (En —N02 + R-CNO)... 

Oxazol 2-Chlormethyl-5-methoxy-4-(4-nitro-phenyl)- E8a, 907 (ROOC—CN2 —Ar +... 

Oxazol-2-Aniou 5-(2-Acetoxy-5-nitro-phenyl)-4-methoxycarbonyl- E19d, 689 (R-NC + Ar —CO —Cl)... 

Nitro-benzophenon wird an Blei (geteilte Zelle, Athanol/Wasser/Natriumacetat) zu 3-Phenyl-(benzo-[c]-l,2-oxazol) (86% d.Th.) cyclisiert4 ... 

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. 

Oxazol 5-(3,4-Dimethoxy-phenyl)-4,5-dihydro- E7a, 651 (R-NCO + R-Li/Ar-CHO) Pentan 4-Nitro-l-oxo-l-phenyl- X/l,... 

The dipole moments of the oxazole molecule determined by dielectric218 and Stark-effect measurements in the microwave spectrum233 are 1.4 and 1.5 0.1 D, respectively. On the basis of small inertial defects in oxazole, Mackrodt et al.m have concluded that the molecule is planar. There is a complete lack of data on the dipole moment of simple alkyl-substituted oxazoles. On the other hand, the values of the dipole moments of a number of aryl-substituted oxazoles have been reported (see Table V). As might be expected, a nitro substituent into the para position of a phenyl ring attached to oxazole increases the value of dipole moment by 2.0-3.5 D. 

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