Pyrazolo triazole, 2-phenyl

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). 

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-... 

Triplet energy transfer measurements from porphyrin and phthalocyanine sensitizers give the triplet energies of six (Z)-A4,A4-diethyl-2-(alkyl, aryl)-A1-(3-phenyl-77/-pyrazolo[5,l-r-][l,2,4]triazol-7-ylidene)benzene-l,4-diamine azomethine dyes 154 with adsorption maxima in ethanol at 546-633 nm to lie in the range of 115-88 kJmoF1 <2003PPS563> (Figure 24). 

The reaction of 6-methyl-3-phenyl-(l//)pyrazolo[5,l-c][l,2,4]triazole 56 with phenyldiazonium chloride affords 177-6-methyl-3-phenyl-7-phenylazo-pyrazolo[3,2-f][l,2,4]triazole 183 the structure of this compound was unequivocally assigned when compared with an identical product prepared in the reaction of compound 56 with acetic anhydride followed by azo coupling and basic hydrolysis (Scheme 5) <2003RRC533>. 

The reaction of iV-amino-2-chloro-5-phenyl[l,2,4]triazole 364 with malonodinitrile, in the presence of triethylamine, in refluxing ethanol gives intermediate 365 that spontaneously cyclized to give 6-amino-7-cyano-3-phenyl-pyrazolo[5,l-c][l,2,4]triazole 62 in 70% yield (Equation 69) <1996SC3827>. 

The reaction of 2-anilino-l,4-naphthoquinone 374 with benzoylacetic acid hydrazide gives 3-hydrazino-pyrazolyl derivative 375, that is acetylated to produce 5-[[l,4-dihydro-l,4-dioxo-3-(phenylamino)-2-naphthalenyl]sulfonyl]-3-methyl-6-phenyl-5/7-pyrazolo[5,l-c][l,2,4]triazole 51. This latter derivative is also obtained in 51% yield from reaction of 374 with benzoylacetic acid hydrazide in the presence of a mixture of acetic acid-sodium acetate <2004PS(179)1907> (Scheme 39). 

Alkenylidene cyclopropanes react readily with 246 to yield 1,4-diazo-bicyclo[3,3,0]oxtanes, whereas methylidene cyclopropane reacts only very slowly with 246 to yield a 2 + 2 cycloadduct (73AJ1553). Compound 246 also reacts with 5-methylfuran-2(3//)-one in an acyl-ene reaction to yield 7-acetyl-6,7-dihydro-2-phenyl-2.ff-pyrazolo[I,2-a]-l,2,4,-triazol-l,3, 5-trione [80JCS(P1)843]. 

Methyl 7-Methyl-l,3-dioxo-2-phenyl-2,3,6,7 tetrahydro-5,6-methano-l//,5//-pyrazolo l,2- ] l,2,4 triazole-5-carboxylate (310 Typical Procedure, Thermal Synthesis 45... 

The diazopyrazole (93) with various phosphorus ylides afforded 3/7-pyrazolo[5,l-c]-1,2,4-triazoles (94) by elimination of triphenylphosphine (79TL1567). Reaction of 1-chloroisoquinoline with 5-phenyltetrazole gives 3-phenyl-1,2,4-triazolo[3,4-a]isoquinoline (96) via intermediate (95) (70CB1918) (cf conversion 86 — 87). 

Unexpected results lead to the discovery of pyrazolo[4,3-r/][2,3]benzodiazepine 87 preparation from l -(/V,Ar-diaroyl)-amino-4-phenyl-[l,2,3]triazol-5-yl-methyltriphenylphosphonium ylide 85. Ylide formation was followed by a Dimroth-type rearrangement to 86 and to product 87 <1995TL5637> (Scheme 17). 

Benzoylamido-4-diazo-l-methyl-3-phenylpyrazole (62a), which exists in the zwitterionic form, reacted under alkaline conditions to furnish 4-methyl-6-phenyl-3,4-dihydropyrazolo[3,4-reaction product (Scheme 12). This reaction, which is believed to proceed via a 5-amino-4-diazo intermediate (63), needs to be carried out in the dark since compound (62a) itself is very sensitive to irradiation <84H(22)2309>. The urea derivatives (62b,c) react analogously, affording compound (64b) after a short reflux in KOH solution. Treatment of the same substrate with triethylamine yielded the carboxyamides (65b,c), hydrolysis of which gave the unsubstituted pyrazolo[3,4-. 

When the 1 -aroyamino-4-phenyl-l, 2,3-triazol-5-yl-aroylmethylphospho-rus ylide was boiled under reflux in xylene or chlorobenzene, it rearranged to the pyrazolo[4.3-rf][2,3]benzodiazepines (95TL5637) (Scheme 93a). The mechanism involved a ring opening of the triazole and a recyclization to a pyrazole (Scheme 93A). 

Aryl-6-phenyl-2-methylthio/secondary amino substituted-4(3//)-pyrimidinones were derived from a reaction of N-arylamino substituted 1,3-diaza-1,3-butadienes with substituted ketenes that was analyzed by computational methods <97T13829>. 1,3-Diazines related to 6-amino-4-chloro-5-cyano-2-(dimethylamino)pyrimidine were prepared in one-pot fashion from 1,1-diamino-2,2-dicyanoethylene and phosgeniminium chloride <97SC1223>. Pyrazolo[3,4- /]pyrimidines were derived from 4-substituted 5-aminopyrazole-l-carbothioamides <97JCR(S)352>. Amino-5-(trifluoromethyl)-l,2,4-triazole gave polysubstituted 2-... 

By reacting 3-thiol-5-phenyl-4-pyrrolyl-1,3,4-triazole (160) with chloroacetic acid or phenacyl bromide, the 3-carboxymethylthio- (161) and 3-phenacylthiotriazole (162) were obtained, and underwent intramolecular cyclization reactions via electrophilic substitutions. The cyclization of the former in boiling ppa produced thiadiazepinone (163) (38% yield), while the latter was cyclized to the phenyl derivative (164) (50% yield), 3,9-diphenyl-l,2,4-triazolo[3,4-t]pyrazolo[l,2-d]-l,3,4-thiadiazepine, by heating with phosphorus oxychloride (Scheme 28) <82G345>. 

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