* by organic reduction at an electrode
* by mild reducing agents such as ascorbic acid (vitamin C)
* by gamma radiation from solvated electrons generated in water
* photoinduced electron transfer
* reduction by metal cations, most commonly a cuprous salt.
* anion-induced dediazoniation: a counterion such as iodine gives electron transfer to the diazonium cation forming the aryl radical and an iodine radical
* solvent-induced dediazoniation with solvent serving as electron donor