Witt diazotization

The first important event in the history of azo pigments was the discovery of the diazotization reaction by P. Cries in 1858. In 1875, Caro and Witt synthesized chrysoidine,... 

The preparation of the first cationic azo dye, Vesuvin, was described by C. Martius in 1863. It is obtained by coupling diazotized m-phenylcncdiamine to an excess of the same amine. An analogous dye from toluylenediamine was reported by P. Gries in 1878. Chrysoidines, coupling products of aniline or toluidines to m-phenylenediamine or toluylenediamine, were reported by H. Caro in 1875 and O. N. Witt in 1876. 

Pure o- and p- dinitrobenzenes may be obtained from the corresponding nitro-anilines in two ways either by diazotization (Meisenheimer and Patzig [34],) or by oxidation (Bamberger and Hiibner [35], Witt and Kopetschni [36]) ... 

Knoevenagel (see Witt and Knoevenagel Diazotization Methods) Knoevenagel Condensation Knoop-Oesterlin Amino Acid Synthesis Knorr (see Koenigs-Knorr Synthesis)... 

Griess Diazo Reaction Witt and Knoevenagel Diazotization Methods... 

The diazonium cation prepared from 4-aminopyridine by Witt s method couples with phenols 448 and with primary aromatic amines3 3, but the value of this method in the coupling with dimethylaniline is doubt-ful389. 2-Aminopyridine fails also, and indeed no 2-pyridyl azo compounds have been obtained directly by diazotization and coupling. Successful coupling of dimethylaniline to pyridine-4-diazonium cation prepared in a mixture of phosphoric and nitric acids has been reported oec ... 

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