3-Hydroxy-1,2,3-benzotriazin-4-one, 1, was prepared by diazotization of o-aminob-enz-hydroxamic acid, 2. 3-Methoxy-1,2,3-benzotriazin-4-one, 5a, was obtained by reaction of 1 with dimethyl sulphate and was found to be stable to thermolysis. Acetylation and benzoylation of 1 yielded the N-acetoxy-5b and benzoyloxy-5c derivatives respectively. The N-benzoyloxy derivative 5c is converted into the acetate 5b by a novel 'acyl-exchange' reaction in acetic anhydride. Acid hydrolysis of 1 gives anthranilic acid, and thermolyses of 1 in amyl alcohol and aniline afford amyl anthranilate and N-phenylanthranilamide, respectively. The ketenimine 11 is postulated as an intermediate in the thermal breakdown of 1, and this is confirmed by the isolation of the Diels–Alder adduct 12 from reaction of 1 with phenyl isocyanate. Thermolysis of 1 in inert solvents affords a novel compound, 3-(o-aminobenzoyloxy)-1,2,3-benzotriazin-4-one, 6, which polymerizes when 1 is subjected to prolonged thermolysis in diglyme. 6 resisted methylation and acid hydrolysis, but underwent acyl-oxygen cleavage when diazotization of 6 was attempted and suffered 'acyl-exchange' when acylation was attempted. The formation of 6 from 1 also involves the ketenimine 11. The importance of these observations to an understanding of previously reported reactions of benzotriazinones is discussed. The o-aminobenzoyloxy derivative 6 shows potential as an o-aminobenzoylating agent.

Treatment of the diazonium salts, X•C6H4N2+, with aqueous methylamine affords good yields of the monomethyltriazenes, X•C6H4•N=N•NHMe, when the substituent is a strongly electron-withdrawing group (X = o-, m-, and p-NO2; o-, m-, and p-CO2R; p-CN and p-COCH3). Preparation of the triazene from the p-bromobenzene diazonium salt was accompanied by formation of a pentaazadiene. Monomethyltriazenes were not obtained when diazonium salts containing other substituents (X = H, p-CH3, o-CF3, p-Cl, p-F, p-NMe2, p-OH, p-OCH3, p-Ph, p-NHCOCH3) were treated with methylamine. In these cases the products were either pentaazadiene, or 1,3-diaryltriazenes or unstable materials. The monomethyltriazenes vary considerably in stability and give rise to a number of different degradation products, which were either diaryltriazenes or 3-alkyl-1,3-diaryltriazenes or simply arylamines. 1(3)-(p-Nitrophenyl)-3(1)-methyltriazene was found to be a moderately effective methylating agent.

The formation of isolable l-aryl-3-methyltriazenes in the coupling reaction of arenediazonium salts with methylamine is favoured by the presence of electronwithdrawing substituents in the aryl group. TRIAZENE synthesis by diazo-coupling to nitrogen is often cited in organic chemistry text-books1 as being generally applicable to primary and secondary, aliphatic or aromatic, amines. However, reviews of diazo-chemistry2 suggest that coupling with a primary aliphatic amine [reaction (l)] leads to formation of a penta-azadiene (2) and that the ArNa + RNH, + ArN=N-NHR The meta-and para-substituted triazenes (4, b-e, g),

Mercaptide/alkoxide competition in substitution and addition reactions is discussed as it applies to the preparation of disulfides. Oxidation of an asymmetric disulfide with H2O2 is shown to exhibit high regioselectivity which may be rationalized in the same terms employed for other sulfide oxidations, viz. substituent electron withdrawing ability (Xp) and steric effects.

Application of mercaptide anions to the dechlorination of an α-polychlorosulfonyl substrate has provided the key step in a successful synthesis of the title compound. 5-Phenyl-2,4,5-trithiapentane-2,2-dioxide undergoes chlorinolysis in an aqueous medium to yield products consistent with the view that α-sulfonyl oxodichlorosulfonium chlorides and α-sulfonyl dichlorosulfonium chlorides may undergo unusually facile Pummerer rearrangements.