Heteroaromatic reactivity. Part VII. The kinetics, products, and mechanism of nitration of some 1-arylpyrazoles and 1-phenylimidazole
- 1 January 1972
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 11,p. 1654-1660
- https://doi.org/10.1039/p29720001654
Abstract
The nitration in sulphuric acid of some 1-arylpyrazoles, and of 1-phenylimidazole, to give substitution in the carbocyclic rings is shown to involve the cations of the bases. Methyl groups at N-2 or C-5 in the 1-arylpyrazoles reduce reactivity in nitration by steric hindrance to the coplanarity of the aryl and heterocyclic group. Nitration of 1-arylpyrazoles in acetic anhydride generally gives poor yields of mononitro-compounds substituted at C-4 of the pyrazole ring. However, 5-methyl-1-phenylpyrazole gives both 5-methyl-3- and 5-methyl-4-nitro-1-phenylpyrazole. The poor yields prevent a definite assignment of mechanism; some possibilities are briefly discussed.Keywords
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