Hypophosphorus acid, deamination diazonium salts

The Hypophosphorus Acid Deamination of Diazonium Salts in Deuterium... 

An effective reagent is aqueous hypophosphorus acid, and an example of its use has been described in detail for the synthesis of 3,3 -dimethylbiphenyl from 4,4 -diamino-3,3 -dimethylbiphenyl (o-tolidine).30 As the latter compound is carcinogenic its preparation is ill-advised. More recently the deamination of diazonium salts with t-butyl nitrite in dimethylformamide has been shown to have wide applicability.31 The reaction proceeds smoothly at 65 °C with the evolution of nitrogen gas, the volume of which may be measured and used to monitor the reaction. The mechanism of the reaction is thought to involve the following radical sequence in which the solvent (DMF = solH), is the hydrogen donor. 

Reduction of the Diazonium Group to Hydrogen Deamination of Anilines Hypophosphorus acid (H3PO2) reacts with arenediazonium salts, replacing the diazonium group with a hydrogen. In effect, this is a reduction of the arenediazonium ion. 

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