1-Phenyl-1,2,3-triazole-4-carboxylic acid

Most 1,2,3-triazolecarboxylic acids lose carbon dioxide when heated above the melting point. These reactions are often useful for the preparation of simpler triazoles, for example, in the synthesis of 1-vinyl-triazoles by decarboxylation of the corresponding 4-carboxylic acids. 4,5-Dicarboxylic acids normally lose 2 moles of carbon dioxide on heating above the melting point this is so, for example, with the u-triazole and with the 1-benzyltriazole but l-phenyltriazole-4,5-dicarboxylic acid preferentially decarboxylates at the 5-position, giving the 4-carboxylic acid. 6-Methyl-l-phenyl-4-carboxylic acid is reported to be de-carboxylated slowly in boiling benzene. ... 

Triazole-l-carboxylic acid, 4-phenyl-, ethyl ester... 

Triazole-4-carboxylic acid, 5-chloro-1-phenyl-UV, 5, 685 (55JA6532)... 

Triazole-4-carboxylic acid, 2-phenyl-cleavage reactions, 5, 697... 

NNN/ 4-methyl-3-phenyl-2-phenylcarbamoyloxy-3//,4//-imidazo[l,Z-b [1,2,4]triazole-3a-carboxylic acid ethyl ester 125 and 4,3a-dimethyl-3-phenyl-2-phenylcarbamoyloxy-3//,4//-imidazo[l,2-A [l,2,4]triazole-6-carboxylic acid methyl ester 126 (Table 27) <2001JOC8528>. 

H-1,2,3- and 1//-1,2,4-Triazoles are resistant to base-induced ringopening, but 2-phenyl-l,2,3-triazole-4-carboxylic acid (49) has been decarboxylated and cleaved by heating with barium hydroxide (69AJC1915). 

Hydrolysis of 2-phenyl-[l. 2.3]triazolo[4,5-d]pyrimidine-5,7-dione N-oxides 463 in basic solution gives rise to 4-amino- and 4-ureido-2-phenyl-l,2,3-triazole-5-carboxylic acid 1-oxides 464, as well as their hydrazides and methylamide (2005JGU636) (Scheme 134). 

Treatment of dehydro-L-ascorbic acid (72) with phenyl hydrazine followed by hydroxylamine yielded the hydrazone oxime (73a), cyclization of which in refluxing acetic anhydride gave 4-[l-//u< o-2,3-diacetoxy-(l-hydroxypropyl)]-2-phenyl-l,2,3-triazole-5-carboxylic acid lactone (74a) <77CAR(59)141>. Analogous reactions of the derivatives (72) with substituted aryl hydrazines yielded the triazoles (74b-d). Alternatively, the hydrazone oximes (73a-d) may be treated with HBr in... 

Oxidation of the [4,3-/ ]pyridazine ring system with potassium permanganate occurs by cleavage of the C(7)—C(8) bond. Thus, 3-phenyl-[l,2,4]triazoIo[4,3-f)]pyridazine was oxidized to 3-phenyl-l,2,4-triazole-5-carboxylic acid (74MI41501). 

Oxidation of 2-phenyl-[l,2,4]triazolo[l,5-6]pyridazine with potassium permanganate yielded 3-phenyl-l,2,4-triazole-5-carboxylic acid (74MI41501). 

---