1.2.4- Triazolo indazoles

Saito et ai, this principle was then applied by Molina and his group to a broad range of molecules (94S1197). Thus, diazide 340 was transformed via a Staudinger reaction to bisiminophosphorane 341 with partial cyclization to l//-l,2,4-triazolo indazole (Scheme 124). Treatment with ethyl isocyanate leads to a pentacyclic 1,3,5-benzotriazepine (343) in 52% yield. With other isothiocyanates the yield can be improved to 82% (91TL2979 92T3091 94S1197). 

An efficient solid-phase synthesis of [l,2,4]triazolo[l,5-7]indazoles has been described starting from bis(azide) 367. The coupling of this compound with polymer-bound triphenylphosphine gives compound 368. This unprecedented bis(iminophosphorane) reacts with various isothiacyanates to give the corresponding iminophosphoranes 215 (unreported yields) attached to the resin (Scheme 37) <2000SL1411>. 

Anodic oxidation of substituted hydrazones may induce ring closure. Oxidation of /7flrfl-substituted phenylhydrazones of 2-oxophenylacetonitrile yields derivatives of 1-phenyl-3-cyano-l/7-indazoles [73] p-nitrobenzylidene-o-phenylenediamine is oxidized in MeCN-LiC104 to 2-(pnitrophenyl)benzimidazole [74], chalchone phenylhydrazone in MeCN-C5H5N-LiC104 to 1,3,5-triphenylpyrazol [74], and benzylidene 2-pyridylhydra-zone (XXIV) to 3-phenyl-j -triazolo[4,3-a]pyridine (XXV) oxazoles and imidazoles may be prepared similarly [74] ... 

The most attractive application of the 3//-indazole route is the synthesis of the first cyclo-propapyridine In contrast, the biradicals formed upon irradiation of 9,9-dimethyl-9//-l,2,4-triazolo[h]pyrazolo[4,3-<7]pyridazines 5 did not cyclize to a cyclopropa[<7]pyridazine-type Structure. ... 

Die Staudinger-Reaktion von 3-Anilino-2-(triphenylphosphoranyliden-amino)-2H-indazol mit Arylisocyanaten fiihrt unter intermediarer Carbodiimid-Bildung zu 2-(4-Methyl-anilino)-1-phenyl-lH-(l,2,4-triazolo[2,3-b]indazoiy [56% Schmp. 218-219 (Toluol)]730 ... 

Diazo-3H-indazol reagiert mit Diaryl-diazo-methanen in einer [11+1 ]-Cycloreaktion zu kon-densierten 1,2,4-Triazolen. So erhalt man mit Diazo-diphenyl-methan 3,3-Di.phenyl-3H-(l,2,4-triazolo[4,3-b]indazoiy472 [87% Schmp. 204 205° (Ethanol/Benzol)] ... 

Dialkyl-diazo-methane reagieren nicht durch Cycloaddition, so daB hier eine andere Synthe-seroute eingeschlagen werden muB. 3-Hydrazino-lH-indazole werden mit Dialkylketonen zu den entsprechenden Hydrazonen kondensiert und dann durch Dehydrierung mit Blei(I V)-acetat zu Triazoloindazolen cyclisiert472. Aus Aceton und 3-Hydrazino-lH-indazol erhalt man so 3,3-Dimclhyl-3H-(l,2,4-triazolo[4.3-b indazoiy (R = CH3)472 [55% Schmp. 66—67 (Petrol-ether/Diethylether)]. 

Die aus 3-Hydroxy-lH-indazolen und Carbonsaure-chlorid-hydraziden zuganglichen 2-(l-Arylhydrazono-alkyl)-3-oxo-2H-indazole cyclisieren beim Erhitzen in Mineralsauren zu 3-Acy 1-1-aryT1 H-< 1,2,4-triazolo[4,3-b]indazolen>574 z. B.574 ... 

Acetyl-1-phenyl- II-(1,2,4-triazolo[43-b] indazol> 80% Schmp. 210° (Buianoi)... 

A reported example of these compounds, namely l,2,4-triazolo[4,3-6]indazole (59), was synthesized (76H1655) by the cycloaddition of C-acetyl-N-phenylnitrilimine (58) to l-methylindazole (57). 

The 3-(A -acyl-JV-benzylamino-2-(triphenylphosphoranylidene)-amino-2/f-indazoles (228) on treatment with concentrated hydrochloric acid cyclize to 2-alkyl-1-benzyl-l/f-[l,2,4]triazolo-[l,5-h]indazoles (229) (Equation (61)) <90JOC4724>. 

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