Azobenzene Benzimidazole

The photolysis of the meso-ionic 1,4-diphenyl-1,2,4-triazol-3-one (200, R1 = R3 = Ph, R2 = H) was stated97 to yield phenyl isocyanate (13%), iV.N -diphenylurea (23%), and the bicyclic compound 215 (49%). These results were interpreted in terms of the fragmentation of the photo-intermediate 213 yielding the JV-phenyldiazirine (214).97 A later publication by the same group97b reports different results. Photolysis of meso-ionic 1,4-diphenyl-1,2,4-triazol-3-one (200, R1 = R3 = Ph, R2 = H) was stated to yield97 phenylisocyanate and the bicyclic compound 215. Later studies,7b have shown that the bicyclic compound 215 is not produced by the photolysis of 200, R1 = R3 = Ph, R2 = H. Irradiation in methanol-methylene chloride gave methyl phenylcar-bamate (25%), benzimidazole (18%), and azobenzene (7%). 

Phenylazodiphenylamine A420-R Phenylazobenzoic Acid. See Azobenzene-carboxylic Acid A650-R Phenylazoxybenzoic Acid. See Azoxybenzene-carboxylic Acid A668-L N,N-o-Phenyleneguanidine. See 2-Amino-benzimidazole A187-L Phenylethanolamine. See under Anilinoethanol A424-L... 

H Chemical shifts of azobenzene-like compounds,8-26 ortho-, ortho -dihydroxyazopyrazole27 and diazonium salts coupling products with guaiacol,28 5-aminopyrazole,29 2-phenyl-5-oxazolone,30 3-(4-methoxyphenyl)-1 -oxo- 1H,5H-pyrido[l,2-a]benzimidazole,31 2 - ortho, meta, paru-aminophenyl)oxazolo-... 

Ketones are reduced to alcohols in the phase-transfer catalysed H-transfer reduction with isopropanol, or better PhCH2CH20H, in the presence of Fe3(C0)i2 Fe(C0)5 is far less active. Mono-, di- and trinuclear iron hydride carbonyl anions are generated in situ. a-Trimethylsilylketones can be prepared via Rh catalysed oxidations with butenones (eqn.9). Azobenzene is isomerised and reduced to o-phenylenediamines by a RuCl3/PPh3/C0/Li0Ac system in secondary alcohols. By contrast, n-butanol leads to formation of benzimidazoles (Scheme 3). 

Nitrogen Systems.—A review on the synthesis of pyrrolo[l,2-a]indoles (754) and related systems has appeared. Treatment of azobenzene (755) with 2,6-dimethylphenyl isocyanide (756) in the presence of dicobalt octacarbonyl yields a mixture of the imino-indazoline (757) and the indazolo-indazole (758)." Heating 5-amino-l-o-chlorophenyl-pyrazoles (759 R = CN or C02Et) in DMF in the presence of copper oxide yields the pyrazolo-benzimidazoles (760)." ... 

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