Benzotriazole 2- aryl-7-nitro

Nitro-azobenzole werden primar zu den analogen Hydrazobenzolen reduziert. In Ammoniakpuffer-Losung bildet sich an Quecksilber bei —0,5 bis —0,65 V quantitativ das 2-Aryl-2H-benzotriazol-l-oxid. Bei —1,0 bis —1,4 V entsteht ebenfalls quantitativ das... 

The VNS is the reaction of choice for incorporation of a-sulfonylalkyl substituents into nitroarenes and their heteroanalogues. Particularly accessible and useful are nitroarylmethyl phenyl sulfones and their heteroanalogues that are efficiently produced in the VNS reactions of carbanions of chloromethyl aryl sulfones with a great variety of nitroarenes and nitroheteroarenes. Nitro derivatives of heterocycles, such as pyrrole [54,55], furan [54], thiophene [54], imidazole [106, 112, 113], pyrazole [114], pyridine [57], indole [115], indazole [116, 117], benzimidazole [118], benzotriazole [119], benzofuroxan [120], quinoline [121], and porphyrins [122, 123], have been shown to enter this reaction. 

The reduction of several indolo[2,3-a]quinolizidines by BY gave novel products resulting from reduction of the indole double bond, cleavage of the C-D ring junction, or reduction of a lactame to a carbinol amine [371]. The known reduction of aromatic nitro compounds has been used as a key step in the synthesis of 2-aryl-2/f-benzotriazoles. Thus, treatment of the o-nitrophenylazo dye 342 gave the 2-aryl-2/7-benzotriazole-l-oxides 343 in good yields [513]. 

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