Oxidation and rearrangement in nitrogen heterocyclic chemistry.
thesisposted on 19.11.2015, 08:47 by Alan A. Sale
This thesis reports a study of the preparation and oxidation of a range of heterocyclic N-amino compounds. A review of N-aminating agents is given in the Introduction. 1,2,4-Triazin-3(2K)-ones gave imidazolin-2-ones when treated with hydroxylamine-o-sulfonic acid or 0-(2,4-dinitrophenyl)hydroxyl- amine , probably via N-amino intermediates. However, chloramine gave 1, 2, 3-triazoles by acting as an oxidising rather than an aminating agent. These reactions were extended to cinnolin-3(2H) - one where the 2-amino derivative could be isolated. Pyrolysis and oxidation of 2-aminocinnolin-3(2K)-one both lead to new rearrangements. l-Aminoquinoxalin-2(IH)-one, prepared by amination of quinoxalin- 2(lK)-one, gave benzo-l,2,4-triazine when oxidised by lead tetraacetate, as well as products derived by interception of the N-nitrene intermediates. Four 3-substituted 1-aminooxindoles were prepared by direct amination and by reduction of cinnolin-3(2H)-ones and their different oxidative decompositions determined. The oxidation of N-amino-acetanilide was investigated for comparison. I-Amino-3-substituted benzimidazolin-2(lH)-ones were similarly studied; the corresponding tetrazenes and deaminated compounds were formed on oxidation and the N-nitrene intermediates could be intercepted with olefins or dimethyl sulfoxide. The unsubstituted l-aminobenzimidazolin-2(lH)-one gave 1-acetylbenzotriazole, however, probably via benzo-l, 2, 4-triazin-3(2H)-one. The decomposition of benzotriazole-l-carboxamide was briefly investigated. This work illustrates the diverse reactions of amino-nitrenes; generated by dehydrogenation of 1,1-disubstituted hydrazines, which include deamination, dimerisation, intramolecular rearrangement and the formation of aziridines with olefins.