Benzoxazoles, Benzisoxazoles, and Benzofurazans

The proton spectra of a number of other benzoxazole nitro derivatives are presented in [737, 738], The proton chemical shifts and coupling constants are reported for 2-methyl-5-nitro-, 2-methyl-6-nitrobenzoxazole, and 2-methyl-5-nitrobenzothiazole 

The chemical shifts of their 2-methyl protons satisfactorily correlate with the Hammett substituent constants [737], 

The chemical shifts and coupling constants of the products of nitration of 3-alkyl- and 3,6-disubstituted 1,2-benzisoxazoles point to the formation of 5-nitro- and 5,7-dinitro derivatives, respectively [739], With 3,5-disubstituted 1,2-benzisoxazoles only 4-nitro compound is formed, the 3,7-disubstituted derivatives being nitrated to the corresponding 5-nitrobenzisoxazoles [739], In studying the kinetics of 3-methyl-l,2-benzisoxazole nitration the proton spectra of both nitrated benzisox-azole and its salt, 2,3-dimethyl-5-nitro-l,2-benzisoxazolium tetrafluoroborate, have been recorded [740], 

The structures of 5-nitro- [741] and 6-nitro-l,2-benzisoxazole-3-acetic acid, 6-nitro-l,2-benzisoxazole-3-yl acetonitrile [742], 6-nitro-l,2-benzisoxazole-3-carboxylates [742, 743] and 6-nitro-4-(R-sulfonyl)benzisoxazoles [744], 3-dini-tromethyl-5-nitro-l,2-benzisoxazoleandbis(5-nitro-l,2-benzisoxazol-3-yl)furoxan [741] were established with the use of proton spectra. 

The oxidation of anionic a-complexes of 1,3,5-trinitrobenzene with an oxidative CuBr/CCl4 system led to the formation of 3-organyl-4,6-dinitroanthranyls (2,1-ben-zisoxazoles) the structure of which was proved by PMR, IR spectroscopy, and mass spectrometry [745], 

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