Synthesis of arylhydrazones using stable diazonium salts and dimedone, malononitrile or ethyl acetoacetate under mild conditions

Diazonium salts are useful synthetic building blocks in organic synthesis because these compounds can be linked to methine or aromatic sp2-hybridized C-atoms. The diazotization and diazo coupling reactions are usually carried out with protonation of nitrous acid under strongly acidic conditions, and azo coupling carried out at low temperature in the presence of nucleophilic coupling components [1]. Although satisfactory yields of products are usually obtained, the diazotization and diazo coupling reactions are complicated by numerous competing reactions. For example, reaction temperatures above 10 °C generally promote phenol formation in aqueous media, and subsequent coupling of the phenol with undecomposed diazonium salts produces azophenols. Moreover, because of this instability, subsequent reactions with diazoniumsalts must be carried out under the same conditions that these saltsare formed. Thus, aryldiazonium salts with higher stability andversatility that can be easily made and stored under solid stateconditions with explosion-proof properties are desired andnecessary.In continuation of our studies on the application of stable diazonium salts [2,3[, herein, we wish to report a convenient and rapid method for the synthesis of some arylhydrazonesusing aryl diazonium silica sulfates in the presence of dimedone, malononitrile and ethyl acetoacetate under mild conditions. The use of inexpensive materials, simple and clean work-up, short reaction times and good yields are advantages of this method.