Aromatic-triazine ring structures

Electronic structures of 1,2,3,5-thiatriazepine-l, 1-dioxide 1 and 1,2,3,5-benzothiatriazepine-l,1-dioxide 2 were studied <1995NJC325>. The dioxide 1 (Figure 4) is formally a homoaromatic analog of 1,2,4-triazine, which is known to be aromatic however, electronic structure calculations, conducted at the HF/6-31G and MP2/6-31G levels, indicated that 1,2,3,5-thiatriazepin-l,1-dioxide is neither planar nor aromatic. The lack of aromaticity in 1,2,3,5-thiatriazepin-1,1-dioxide is reflected in bond lengths and covalent bond orders that exhibit a large degree of alternation. Similar conclusions were reached for the 1,2,3,5-benzothiatriazepine-l,1-dioxide 2, in which only the benzene ring is found to be aromatic. 

Nitroquinoline 209 enters into a direct cyclocondensation with aromatic hydra-zones in NaOH/DMF giving pyrazolo[3,4-/]quinolines 210 and (or) triazino[6,5-/ quinolines 211 in low to moderate yield (Scheme 62) (OOOL413). Their ratio mainly depends on the structure of the starting hydrazone. For example, electron-donating substituents in its aryl moiety assist triazine ring closure. Evidently, pyrazoles 210 are products of two consecutive SNH and SN ipso reactions, whereas conversion of 209 into 211 looks rather complicated and better corresponds with cascade hetero-cyclizations considered in Section III.D.l. 

In Table 19.3, the total gas evolved for different species was obtained by integrating the instantaneous values in time. In nitrogen, the amount of H20 evolved increases with the inclusion of the NC when PA6 is compared with PA6 + NC and PA6 + FR with PA6 + FR + NC. This is likely caused by the liberation of water from clay. The same trend is observed for NH3 while the opposite trend is apparent for C02. In the case of PA6 + FR + NC, the increase in NH3 might be partly caused by the evolution of water and consequent hydrolysis of the triazine ring, which in subsequent steps produces cyanuric acid and finally ammonia and carbon dioxide. The decreased levels of C02 might be related to a difference in the degradation pathways and possibly trapping of hydrocarbons and production of an aromatic char structure [12]. In the air, the fractions will depend on oxidation... 

New aromatic poly(monosulfide)s (10) (34) containing a 1,3,5-triazine ring were readily prepared with moderate yields by the aromatic nucleophilic substitution polymerization of 2,4-dichloro-l,3,5-triazine derivatives with bis(4-mercaptophenyl) sulfide (4,4 -thiodibenzenethiol) [19362-77-7] under mild conditions in the presence of a base in tetrahydrofuran (THF) [109-99-9] solution or in the o-dichlorobenzene/water two-phase system by using phase-transfer catalyst. The resulting polymers showed highly crystalline structures and high thermal stability (Td 330-410). 

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