Pyrazolo triazole

In the reactions with phosphonio-a-methoxycarbonyl-alkanides, the products of type 261 derived from 1,3-cycloaddition can rearrange to the tautomeric lif-pyrazolo-triazole (87MI2). The reaction of 3-diazopyra-zoles and 3-diazoindazole with acyl-substituted phosphonium ylides led to pyrazolo-triazine and indazolo-triazine derivatives 266 instead of the expected triazole compounds (8IJHC675). In this case, the ylides, which can exist as phosphonium enolates, possess nucleophilic and electrophilic centers in a /8-relationship, giving [7 + 2] or [11 -I- 2]cycloaddition reactions. With dimethylsulfonio-a-aroyl-methanides, very complex, temperature-dependent mixtures were obtained, in some cases with sulfur retention (87MI3). 

Imidazo[4,5-c]pyrazole 4-oxides (762 R = p-N02CeH4) are obtained by base-catalysed cyclisation of the nitro-pyrazoles (761).Cyclisation of the pyrazolylhydrazone (763) gives either the pyrazolo-triazole (764) or the pyrazolo-triazine (765), depending on conditions. ... 

Oxidation of the hydrazone of 2-hydrazinopyrazole (226) with Pb(OAc)4 in CH2CI2 is a two-step reaction. The azine (227) was formed as an intermediate and this underwent ring closure to the 3H-pyrazolo[5,l-c][l,2,4]triazole (228) (79TL1567). A similar reaction applied to the benzal derivative of 2-hydrazinobenzothiazole (229) gave 3-phenyl-[l,2,4]triazolo[3,4-6]benzothiazole (230) together with a by-product (231) (72JCS(P1)1519). 

An interesting application of a phosphorus ylide in heterocyclic synthesis is in a ring annulation. The diazopyrazole (592) when treated with various phosphorus ylides gave the 3//-pyrazolo[5,l-c][l,2,4]triazole derivatives (593) with elimination of triphenylphosphine (79TL1567). 

However, there are differences between o-phenylenediamine and 4,5-diaminopyrazoles in the synthesis of [5.5] systems. For example, the formation of pyrazolo[3,4-d]-[l,2,3]triazole (550) is similar to that of benzotriazole, but all attempts to extend the synthesis of benzimidazoles to the preparation of the imidazo[4,5-c]pyrazole system (551) have failed (78TH40400). 

Pyrazolo[3,2-c][l,2,4]triazole-7-carboxylic acid synthesis, 6, 1018 Pyrazolotriazoles dye releasers... 

Dipole moments and total energies for pyrazolo[l,5-h]-s-triazole tautomeric forms 97a-97c were calculated using CNDO/2 and CNDO/S (76T341) the results predict the stability of tautomers in a 97a > 97b > 97c sequence. So far, no ab initio calculations or synthesis of 97 have been reported. For pyrazolo[3,2-c]-s-triazole 98 (76T341), the calculated dipole moments, electronic absorption, and proton chemical shifts are in a good... 

Pyrazolo[l,2- ][l,2,3]triazole mesomeric betaines are generally available by an electrophilic attack of singlet nitrenes on the pyrazole nitrogen atom. When phthalazone derivative 252 is used and the nitrene is generated by reduction with triethyl phosphite, 59% yield of mesomeric betaine 253 is obtained (Equation 40) <2000T5523>. 

Synthesis of cross-conjugated mesomeric betaines containing l-oxo-l//-pyrazolo[l,2-tf]pyrazol-4-ium-3-olate, 1-oxo-1 //-pyrazolof 11.2,4]triazol-4-ium-3-olate, 7-oxo-7//-pyrazolo[l,2-tf][l,2,4]triazol-4-ium-5-olate, 7-oxo-7.//-pyrazolo[ 1.2-//][ 1.2.3 ]mazol-4-ium-5-olate, 3-oxo-3//-pyrazolo[l,2- ][l,2,3,5]thiatriazol-8-ium-l-olate, and 2-hydroxy-pyrazolof 1.2-//][ 1.2.5]m.izin-5-iumH-olate structures was duly covered in CHEC-II(1996) <1996CHEC-II(8)747> and... 

Two kinds of pyrazolotriazole magenta dyes are used in color photographic materials. One is the I //-pyrazolo[5,1 -r]-[l,2,4]triazole skeleton, and the other is the l//-pyrazolo[ 1,5+][ 1,2,4]triazole skeleton as shown in the representative azomethine dye 1 (Figure 1) <1994J(P2)531>. 

Extensive ab initio modeling of the excited states of pyrazolotriazole dyes such as (X)-/V -(3,6-dirncthyl-7//-pyrazolo[5, l-c][l,2,4]triazol-7-ylidene)-./V4,./V4-dimethylbenzene-l,4-diamine 2 and (Z)-A,l-(2,6-dirnethyl-7//-pyra-zolo[l,5- ][l,2,4]triazol-7-ylidene)-iV4,./V4-dimethylbenzene-l,4-diamine 3 (Figure 1) have been carried out, highlighting the value of the computational models in predicting actual chemical behavior, even in a relatively difficult case such as that of the chemistry of excited states <2001J(P2)953>. 

Aryl-7-(4 -diethylamino-2 -methylphenyl)imino-6-methyl-pyrazolo[5,1-r] [1,2,4]triazoles 57 <2002ARK133> 7-ben-zylidenc-6-mcthyl-3-phenylimino-2//-pyrazolo[5,l-r [ 1,2,4]triazole 58 and 6-benzylidene-6-methyl-2-phenyl-3-phenyli-minopyrazolo[5,l -z][ 1,2,4]triazoIe 59 < 1998PS( 134/135)119> 3-phenyIamino(l//)pyrazolo[5,l -r 1,2,4]triazol-6-oI 60 and l-phenyl-3-phenylamino(l//)pyrazolo[5,l-r][l,2,4]triazol-6-ol 61 <1999EJC175> 6-amino-7-cyano-3-phenylpyra-... 

NN/N 3-Aryl-7-arylidene-6-methyl-pyrazolo[5,l-r][l,2,4] triazole 57 <2002ARK133> (Figure 18) 3-aryl-7-ethoxycarbonyl-6-rncthyl-l //-pyrazolo[5,l -r ][ 1,2,4]triazolcs 55 (Table 36) <2002ARK133>. 

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