1.2.3- Benzotriazines decomposition

Alternative procedures for the preparation of 4-alkyl- and 4-aryl-1,2,3-benzotriazines have also been investigated by Rees. Thus, the diazoazide (11) undergoes smooth decomposition in refluxing benzene to give 4-methyl-1,2,3-benzotriazine (8, R = Me) in 70% )deld. Oxidation of the o-aminohydrazones (12, R = Me, Ph,p-MeOCsH4) with lead tetraacetate also gives the corresponding triazines (8) in moderate yield. 

Results available from studies of the photochemical decomposition of benzotriazinones indicate that formation of the reactive species 146 during thermolysis of 10 is a reasonable postulate. Simple 3-alkyl-1,2,3-benzotriazin-4(3/f)-ones (10, R = alkyl) are apparently inert to photo-... 

Thermal decomposition of 3-arylidenamino- (91) and 3-imidoyl-l,2,3-benzotriazin-4-ones (93) in solution gives 2-aryl- (92) and 2,3-diaryl-quinazolin-4( 177)-ones (94) respectively (80JCS(Pl)633,75S187,75S709). In the latter decomposition phenanthridinones (95) are also formed in minor yields. Mechanisms to account for the isolated products were discussed. 3 -Amino-l,2,3-benzotriazin-4-ones (96) in boiling 1-methylnaphthalene yield in all cases... 

Most known 1,2,4-triazines and 1,2,4-benzotriazines are yellow, orange or white compounds, usually crystalline at room temperature. They are mostly stable at room temperature and can be distilled under reduced pressure or recrystallized without decomposition. 

Arylideneamino)-l,2,3-benzotriazin-4-ones 1 undergo thermal decomposition on heating in an inert medium (e.g., paraffin oil) to give the isomeric 2-arylquinazolin-4(3//)-ones 2 in preparative yields. 

When 8-[(4-Cyanophenyl)imino]-87f-quinazolino[3,2-c][l,2,3]benzotriazine (13) is subjected to decomposition in ethanol, acetic acid, mineral acids, or acetic acid containing iodide, bromide, or azide ions, and 2-naphthol, 4-(4-cyanoanilino)-2-[2-(substituted)phenyl]quinazolines 14 are obtained. ... 

Smalley and co-workers obtained the pyrido[2,l- i]quinazolin-l l-one 286 through the thermal decomposition of 3-(2-pyridyl)-1,2,3-benzotriazin-4-one (284) in 1-methylnaphthalene. The pyrido[2,l-i]quinazolinone 286 probably arises from the benzazetinone-iminoketene intermediate 285. Photodecomposition of the benzotriazinone 284 in tetrahydrofuran was very slow. Irradiation for 72 hr furnished the pyridoquinazolinone 286 in less than 5% yield along with the unchanged benzotriazinone 284. 

Thermal decomposition of 3-alkenyl-l,2,3-benzotriazin-4(3/f)-ones leads to 3-substituted quinolin-4(3/f)-ones in reasonable yields.314... 

The thermal decomposition of solid l-methyl-l,4-dihydro-l,2,3-benzotriazin-4-one 59 at >120°C in a stream of argon results in ready loss of N2 with ring contraction to the benzazetinone 60 (Equation 6), which was identified by matrix isolation at 15 K (IR C=0 at 1843 cm ). Irradiation of 60 results in photoreversible ring opening to the iminoketene 61, characterized by an IR band at 2125 cm and a UV absorption centered at 420 nm <1989CC1777>. 

No benzocyclopropenone has been isolated but they appear to be formed as intermediates in the decomposition of benzotriazin-4-ones, in photolysis of 3-p-tolylsulphaminobenzotriazinone [160] or by oxidation of 3-aminobenzotriazinone by lead tetracetate [161]. It is likely that a nitrene is formed initially and collapses, with loss of nitrogen, to form the benzocyclopropenone. Isolated... 

An interesting interconversion is observed between the isomeric triazolo-benzotriazines 268 and 269 under FVP conditions below 550 °C (Scheme 53 2005T7489). At higher temperatures decomposition is observed. Pyrolysis of the 1,2,3-triazole N-oxide 270 unexpectedly affords the di(triazolyl) ethane 271 (2010ARK(x)34). 

---