Benzotriazinium-4-olates

4-olates (261) have been reported. Oxidation of o-nitrobenzaldehyde 

Betaines 261 are stable crystalline compounds. Knowledge of their chemical reactions is still limited. Alkaline hydrolysis of aryl derivatives (261 R = Ar) gives the 2-azobenzoic acids 266 but the mechanism of this rearrangement is unknown. Reduction by tin and hydrochloric acid gives the hydrazides 267. Thermolysis of the /)-tolyl compound (261 R = p-MeC6H4) (120 C at 0.1 mm Hg) gives the isomeric triazine (268 R = -MeC6H4). Phosphorus pentasulfide converts the 2-methyl derivative (261 R = Me) into 2-methyl l,2,3-benzotriazinium-4-thiolate (272 R = Me) (Section III,B,15). 

Wagner and H. Gentzsch, y4rcA. Pharm. lVeinheim,Ger.)3fil,923 (196S)[CA 70,106825 

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Moderate yields of thiones are obtained by treatment of 3,4-dihydro-l,2,3-benzotriazin-4-ones with P4S10 in refluxing pyridine or toluene. The same conditions have been applied to 2-alkyl-l,2,3-benzotriazinium-4-olates, generating the corresponding 4-thiolates <1984CHEC(3)369>. 

For reductive ring contraction of 1,2,3-benzotriazine 3-oxides to 3-aminoindazoles, see Section 9.01.5.6. Reduction of 2-methyl- or 2-aryl-l,2,3-benzotriazinium-4-olate 1-oxides 237 with stannous chloride in concentrated hydrochloric acid/acetic acid at 0-5°C gave benzotriazinium-4-olates 46 (Equation 99) (<1974JOC2710> (A), <1972JOC1587> (B)). 

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