Annelated Triazoles

BBA(342)155>. While this is not a general synthesis of annelated triazoles, it appears to be specific for quinoline-3-diazonium salts. 

In annelated triazoles the Wolfi-rearrangement leads to ring contraction. Thus gas-phase pyrolysis of benzotriazole (9) in a stream of argon gives a 99% yield of... 

Heteropentalenes with annelated imidazole or 1,2,4-triazole ring and one bridge nitrogen atom 98AHC(69)271. 

This chapter describes the chemistry of the simple, nonfused 1,2,4-triazoles including those triazoles annelated by a saturated ring. A resume of the most important points discussed by Polya in the corresponding chapter in the first edition of Comprehensive Heterocyclic Chemistry (CHEC-I) <84CHEC-1(5)733> has been made and a substantial number of the earlier references have been retained, but this account will concentrate on those advances that have been made in this area since the early 1980s. A comprehensive review of 1,2,4-triazole was published in 1981 <8lHC(37)l>. 

Albert, A., 4-Amino-1,2,3-triazoles, 40, 129 The Chemistry of 8-Azapurines( 1,2,3-Triazolo[4,5-d]pyrimidines), 39, 117 Annelation of a Pyrimidine Ring to an Existing Ring, 32, 1 Covalent Hydration in Nitrogen Heterocycles, 20, 117. 

Triazole-based annelations have also been used to prepare 2-phenyl-2/7-[l,2,3]triazolo[4,5-e]py-ridin-4-one (233) from 2-(2-phenyl-l,2,3-triazole)acrylic acid via a thermal Curtius reaction of the a,/J-unsaturated acyl azide (232) (Scheme 43). Further functionalization of the nucleus was accomplished using the intermediate 2//-4-chlorotriazolo[4,5-c]pyridine (234) <85 LA 1922). 

Numerous structures containing the thiocarbonyl ylide dipole are conceivable. Incorporation of the thiocarbonyl ylide dipole into a bicyclic heterocyclic system is possible by the conversion of the cyclic thione (203) into the ring-fused mesoionic system (204). The thiocarbonyl ylide dipole (205) undergoes cycloaddition with both alkenic and alkynic electron-poor dipolarophiles in refluxing benzene or xylene so that, after extrusion of hydrogen sulfide or sulfur, respectively, from the initial 1 1 cycloadducts (206) and (207), a ring-fused pyridinone is formed. The method has been used for the annelation of pyridinones to the imidazole, 1,2,4-triazole, thiazole and 1,3,4-thiadiazole systems... 

We consider azoles as five-membered heteroaromatic compounds and their annelated derivatives containing at least two endocyclic heteroatoms, one of which is nitrogen (pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, oxazole, thiazole, selenazoles, tetrazole, indazole, benzimidazole, benzoxazole, benzothiazole, ben-zoselenazoles, benzotriazole, etc.). 

Aminochromes, 5, 205 Aminomethylenemalonates and their use in heterocyclic synthesis, 54 4-Amino-1,2,3-triazoles, 40, 129 Anils, olefin synthesis with, 23, 171 Anionic cr-adducts of heterocycles, 34, 305 Anions, ring-opening of five-membered heteroaromatic, 41, 41 Annelation of a pyrimidine ring to an existing ring, 32, 1... 

A. Annelation of a Triazole Ring on to an Existing Pyrimidine Ring. 156... 

B. Annelation of a Pyrimidine Ring on to an Existing Triazole Ring. 160... 

As shown in Eq. (93), aryl cyanides can also play a role as bifunctional synthons in similar conversions that lead to annelation of the 1,2,4-triazole ring (83S415 85BCJ735, 85H2613). 

Reaction of thio- and alkylthio derivatives of A -aminoazoles with aryl isothiocyanates leads to annelation of a 1,3,4-thiadiazole or a 1,2,4-triazole ring. Thus, 4-amino-3-methyl-l,2,4-triazoline-5-thione, on reaction with aryl isothiocyanates under mild conditions, gives products of addition (388), which on heating are transformed to 2-arylaminotriazolo[3,4-/>]thia-diazoles (389) (83S411 87JHC1173). 

The use of diarylcarbodiimides as bifunctional amphoteric synthons also leads to annelation of the 1,2,4-triazoles ring. A typical example is the conversion of 2V-aminoimidazole 392 to imidazo[l, 2-b]triazoles 393 (88H161). Similarly, triazolo[4,3-Z>]triazoles 394 have been synthesized from 4-amino-i-triazoline-5-thiones [68JCS(C)2099 88H161]. 

Almost all such cyclizations were carried out with a-thio derivatives of 4-amino- -triazole and 1-aminoimidazole. As cyclizing agents, two groups of compounds were mainly used (1) carboxylic acids and their derivatives, and (2) a-halogenocarbonyl compounds. In the former case, annelation... 

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