Bisazo compounds

It is interesting to note that whereas 7-methoxy-l-methyl-l,2,3,4-tetrahydro-jS-carboline condenses with diazobenzenesulfonic acid to give an azo compound (presumably the 6-arylazo derivative) and 7-methoxy-l-methyl-3,4-dihydro-j8-carbohne gives a bisazo compound, none of the fully aromatic j8-carboline derivatives studied by Perkin and Robinson underwent azo-coupling. 

More than 100 years ago Noelting and Grandmougin (1891) reported that in the azo coupling reaction of equimolar amounts of 1-naphthol and 4-chlorobenzenediazo-nium ion in water, an appreciable amount of the 2,4-bisazo compound is obtained besides the expected 2- and 4-monoarylazo-l-naphthols. The percentage of the 2,4-bisazo compound is particularly high under alkaline conditions (up to 20%). 

Z)- and (ii)-diazocyanides 146 Disazo compounds, see Bisazo compounds Discovery and development of scientific... 

Another method of preparing azobisindolizines is by reaction with tosyl or picryl azide.191-193 2-Methylindolizine is converted into the 3,3 -bisazo compound after 2 minutes. The product yields the radical ion 130 (detected by EPR) when treated with 1 mole of silver perchlorate.194,195 The redox characteristics of such compounds have been studied by Hiinig and co-workers.196,197 In view of the instability of aminoindolizines, they have not been used to prepare diazonium salts. 1-Nitrosoindolizines, however, yield diazonium nitrates in good yield when treated with dry nitric oxide.182,198 The products are stable both in... 

In several papers from Sterba s group azo coupling reactions are described for which intrinsic rate constants close to diffusion control (> 10 1 mol s ) were measured. The coupling components used can, however, not form bisazo compounds. Therefore no mixing effects of the type described in this section were det table. 

CoupB with an aUehyde phenylhydrazone. The coupling of the reagent with trimethylacetaldehyde phenylhydrazone in pyridine-DMF gives the bisazo compound (I), which is rearranged by a strong base to the formazanc (2). Irradiation does not convert (2) into an open, yellow form. 

The Trypan dyes are bisazo compounds distantly related to the sulfonamides. Trypan blue, a bluish-gray, water-soluble powder, was one of the first drugs to be used for the treatment of piroplasmo-sis and trypanosomiasis. Trypan blue is effective against B. caballi but not B. equi. In horses, a freshly prepared 1-2% solution of Trypan blue can be administered by slow i.v. injection at 2-3 mg/kg for premunition. Rapid i.v. administration of Trypan blue may result in shock. Subcutaneous administration of Trypan blue should be avoided because it causes skin sloughing. Trypan blue stains the mucous membranes and other tissues blue and is, therefore, not used commonly. 

Martius, by now a partner in the AGFA firm of Berlin, obtained a sample of chrysoidine (18) and handed it over to his consultant, A.W. Hofmann (Figure 11), for scientific investigation. In January 1877, Hofmann published details of the constitutions, as well as the methods of preparation, for 18, phenylene brown (15) and the related aniline yellow (16), much to the chagrin of Caro and his colleagues33-36. Soon it was shown that phenylene, or Bismarck brown (15), was in fact a bisazo compound 15a (Scheme 6). 

This method was substantially modified latter by Alexandrou and Adamopoulos, who oxidized bissemicarbazones of a-dicarbonyl compounds with lead tetraacetate [Eq. (32)] (76S482). Supposedly, the oxidant is necessary for conversion of bissemicarbazone to bisazo-compound (114), which is transformed to 1-ureidotriazole via triazole betaine (115). If substituents R and R differ, a mixture of two isomeric 1-aminotriazoles is formed, and the isomer with a bulky substituent in position 4 predominates. 

The majority of the direct dyes are bisazo compounds, and the earliest constructive suggestion was made by Meyer in 1928. He expressed the view that substantivity was connected with extended linear molecular structure of the dye so that it could align itself on the surface of the fibre (Peters, Hexagon digest. No. 8). In formula (9) the molecule is linear in the direction of At—B, and is substantive whilst the bisazo compound, formula (10), has no such configuration and is non-substantive. Very many similar examples could be quoted. 

Hydrazo compounds from azo compounds Total and partial reduction of bisazo compounds... 

H chemical shifts were measured of dyes prepared by diazoniiun salt coupling with 2,2, 4,4 -tetrahydroxybenzophenone (mono and bisazo compounds), 3-amino-5-nitro[2,l]benzisothiazole, basic dyes derived from 3-(acetoacetamido)- pyridine, 5-sulfonylpiperidino- and morpholino-8-hydro-xyquinoline, 5,6-dichloro- and 6,7-dichloro-2-aminobenzothiazoles, H-acid, 1 -butyl-3-cyano-6-hydroxy-5-methyl-2( 1 //)pyndone, ethyl-2-hydro-... 

---