Aromatic aminoazo derivatives or triazenes represent a stable aryl diazonium ion source and are thus a class of nitrogen-containing compounds useful for synthetic transformations [1]. In a well-known classical synthesis the aromatic diazoamino system is formed in the reaction between a diazonium cation and the nucleophilic nitrogen atom of an amine. Usually the diazonium salt involved is not isolated, and an acidic aqueous solution of this reagent is exposed directly to the amine at low temperature in the presence of an excess of base to neutralize the acid used for diazotation. However, such diazoamino couplings are frequently accompanied by side reactions, e.g. C-couplings, decomposition of the diazonium salt, etc., leading to formation of multiple products and low yields [2]. Modifications of this synthetic procedure, for example, synthesis on an ion-exchange resin support, have been proposed in order to overcome these complications [3]. These syntheses are further complicated when the aryl diazonium salt is insoluble in water and consequently the coupling reaction has to be performed in a suspension. For example, the syntheses of the sodium salts of 2-, 3-, and 4-(3,3-dimethyltriazeno)benzenesulfonic acid [2] require prior isolation and purification of the corresponding diazonium fluoroborates or fluorophosphates which subsequently are added to a cooled solution of dimethylamine in water under a stream of nitrogen. The products were obtained only after saturation of the reaction mixtures with carbon dioxide. As a result of all this, more convenient methods for the synthesis of novel compounds of this class are highly desirable.