Pyrazolo benzotriazoles

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). 

Photoisomerization of pyrazolo[l,2- ]benzotriazoles 28 was studied in argon matrices at 12 K and in solution at 190 K. On irradiation at 365 nm, 28a and its dimethyl derivative 28b undergo ring closure to yield the triazasemibullvalenes 29a and 29b, respectively, which were identified by NMR and IR spectroscopy. The cyclization is reversed on warming or by irradiation at 313 nm (Equation 2) <2002PPS38>. 

Variation of the ring portion of acyclovir has been achieved. Compounds include monocyclic (isocytosine, triazole, imidazole), bicyclic (adenine, 8-azapurine, pyrrolo[2,3-c/]-pyrimidine, pyrazolo[3,4-[Pg.131]

Indazolo[2,l-a]indazole (dibenzo[6,/]-3a,6a-diazapentalene) IV,B,2 Pyrazolo[l,2-a]benzotriazole (benzo[6]-l,3a,6a-triazapentalene) ... 

A -(Cycloalken-l-yl)pyrazoles 438 were synthesized via elimination of benzotriazole from the corresponding 1-[1-(pyrazolo)cycloalkyl]benzotriazoles 437, prepared from l-(benzotriazolylmethyl)pyrazole 436 (Scheme 49) <2002JOC8230>. The reaction of l-(3,5-dimethylpyrazol-l-yl)acetone 439 with phenyldiazonium chloride afforded the corresponding phenylhydrazone 440, which was converted into pyridazines 441 and 442 by condensation with active methylene nitriles and DMEDMA, respectively (Scheme 50) <2001JHC685>. 

Gilchrist et al. used the reaction of inverse azadiene synthesis to obtain 1 -phthaloylaminopyrazoles (14) from tetrazole (13) and activated acetylene compounds [73CC8I9 75JCS(P1)1747]. Heating l-c>-nitrophenylpyrazoles with triethylphosphite leads to pyrazolo[l,2-a]benzotriazoles [Eq. (2)]... 

Irradiation of l-(2-azidophenyl)-3,5-dimethylpyrazole affords the corresponding nitrene which cyclizes into the corresponding pyrazolo[l,2-u] benzotriazole <91JA6928> (compare with <84CHEC-I(5)167> formulae (341) and (342)). 

Aryl-3,5-dihydroxypyrazoles (543) condense with acetylacetone to afford the novel paraionic 87r-betaines (544). The isomerization (545) -> (546) has been observed. The urazole (547) adds the thioketen NCPhC=C=S to form the heterocycle (548). Dye-sensitized photo-oxygenation of the pyrazolo[l,2-a]benzotriazole (549) yields mainly the epoxide (550). ° ... 

Singlet nitrene, formed by direct irradiation of the pyrazole (125), undergoes cyclization in high yield to give the 5i/-pyrazolo[l,2-a]benzotriazol-4-ium inner salt (126). An alternative reaction pathway is preferred on triplet-sensitized... 

ClgHieNgOs, 6-Acety1-8-(acetyloxyimino)-2-phenyl-4-0X0-4,8-dihydro-2H,6H-pyrazolo[3,4-f]-1,2,3-benzotriazole - dioxane (2 1), 43B, 366 C1gH19CIN2O2S, 1,2,3,4-Tetrahydro-10-methyl-4a-(p-chlorophenylsul-phonylamino)pyrido[1,2-a]indole, 45B, 301 C19H2iN, 3a,4,9,9a-Tetrahydro-2-methyl-4/3-phenylbenz[f]isoindoline, 46B, 280... 

Pyrazole and imidazole are alkylated in high yields on nitrogen with phase-transfer catalysis their A-alkyl derivatives, along with those of 1,2,4-triazole and benzotriazole, have been prepared by treatment of the TV-tributyltin compounds with alkyl halides.A range of A-alkyl-benzothiazolium salts has been synthesized from appropriate alkyl halides and benzothiazole, A-alkyl-phenothiazines (24) are similarly prepared,and some pyrazolo[l,5-a]pyri-midines (25) have been alkylated.In the alkylation of 2,5-dimethyl-3-... 

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