sigma-adduct formation and oxidative substitution in the reactions of 4-nitrobenzofurazan and some derivatives with hydroxide ions in water

Crampton, M.R.; Lunn, R.E.A.; Lucas, D.

Abstract

The reactions of hydroxide ions with 4-nitrobenzofurazan, 1a, 4-nitrobenzofuroxan, 1b, and with three 4-nitro-7-substituted benzofurazans have been examined using H-1 NMR and UV-visible spectroscopies. In each case initial reaction is at the 5-position to give an anionic sigma-adduct. Kinetic and equilibrium results are reported. NMR spectra show that in the case of 1a oxidation of the anionic adduct yields 4-nitro-5-hydroxybenzofurazan. In the case of 1b rearrangement of the 5-hydroxy adduct to the thermodynamically more stable 7-hydroxy adduct, possibly by a Boulton-Katritzky mechanism, precedes oxidation. When the 7-substituent in the 4-nitrobenzofurazan is Cl, OMe or OPh the eventual product is 7-hydroxy-4-nitrobenzofurazan produced by nucleophilic displacement of the substituent.

Citation

Crampton, M., Lunn, R., & Lucas, D. (2003). sigma-adduct formation and oxidative substitution in the reactions of 4-nitrobenzofurazan and some derivatives with hydroxide ions in water. Organic and Biomolecular Chemistry, 1(19), 3438-3443. https://doi.org/10.1039/b307648m

• Journal Article Type: Article
• Publication Date: Aug 1, 2003
• Deposit Date: May 10, 2007
• Journal: Organic and Biomolecular Chemistry
• Print ISSN: 1477-0520
• Electronic ISSN: 1477-0539
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 1
• Issue: 19
• Pages: 3438-3443
• DOI: https://doi.org/10.1039/b307648m
• Public URL: https://durham-repository.worktribe.com/output/1603002