1.2.3- Triazine hydrolytic ring cleavage

Polyaza rings suffer complete hydrolytic ring cleavage. Monocyclic 1,2,3-triazines are hydrolyzed by acid to yield 1,3-dicarbonyl compounds (Scheme 15). 1,2,3-Benzotriazines are easily converted into derivatives of 2-aminobenzaldehyde. 1,2,4,5-Tetrazines (180) are hydrolyzed with a base to give aldehyde hydrazones, RCH = NNHCOR. 

Attempts to prepare this substance by reduction of dioxotetrahydro-1,3,5-triazine with sodium amalgam,hydroiodic acid, or tin in acetic acid, were accompanied by hydrolytic cleavage of the ring. Only... 

Highly substituted pyrrolo[l,2- ][l,2,4]triazines were synthesized from pyrrole derivatives, by closure of the triazine ring. Thus, hydrolytic cleavage of some 1,2-diaminopyrroles having a 1-NH-BOC-protected amino function 43 followed by reaction with 1,2-dicarbonyl compounds afforded a one-pot access to the corresponding bicyclic heterocycles 44 (BOC = f-butoxycarbonyl Equation 6) < 1997J(P 1)1829>. 

Nucleophilic attack at substituted ring carbon is probably the most common reaction of 1,3,4-oxadiazoles. However, few examples have been reported of nucleophilic attack at unsubstituted carbon since such compounds (19a) are relatively uncommon. The mechanism of the well-known conversion of 2-amino-oxadiazoles (in aqueous alkali) into triazoles has been studied in the case of the reaction where (19a R = NHPh) is converted to (20). This proceeds via the anion of semi-carbazide PhNHCONHNHCHO and is initiated by hydroxide attack at C-5 <84JCS(P2)537>. A similar nucleophilic attack by hydroxide on oxadiazole (19a R = 5-pyrazolyl) was followed by cyclization to the pyrazolo-triazine (21). Hydrolytic cleavage of 2-ary 1-1,3,4-oxadiazoles to aroyl-hydrazides allows use of the former as protected hydrazides. Oxadiazole (19a R = 4-... 

Treatment of 2.4,6-tris(difluoromethyl)-l,3,5-triazine with aqueous sodium hydroxide or mineral acids gives three molecules of sodium difluoroacetate (10) by hydrolytic cleavage of the ring system. " ... 

Derivatives of 1,3,5-triazine are important herbicides so that attention has been directed to their persistence particularly in the terrestrial environment. Some examples have been given in Section 5.2.3 of the utilization of amino and thiol substituents of 1,3,5-triazines as sources of nitrogen and sulfur subsequent degradation of these hydroxylated metabolites is mediated by hydrolytic reactions which result in the cleavage of the ring with the formation of C02 and NH4+ (Jutzi et al. 1982). 

New fused tetrazoloazines that have been reported include tetrazolo[5,l-a]isoquinolines,665 tetrazolo[5, l-6]benzothiazoles,666 and tetrazolopyridines.667 Reactions of fused tetrazoloazines, or the azido isomers, that have been reported include hydrolytic cleavage of the pyrimidine ring of tetrazolopyrimidines,66 pyrolysis of 3-azido-pyridazine 2-oxides,66 and photolysis of azido-l,3,5-triazine.670 Dipole moments of 3-azido-1,2,4-triazole derivatives have also been reported.671... 

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