Hydrodediazoniation of Dry Arenediazonium o-Benzenedisulfonimides with Hydrogen Peroxide

This report describes the hydrodediazoniation of dry arenediazonium o-benzenedisulfonimides with hydrogen peroxide in THF at reflux. The new procedure is general, giving positive results in the presence of both electron-donating and electron-withdrawing substituents. Furthermore, it does not suffer from steric effects and always gives the pure reduction products in excellent yields (15 examples, average yield = 93%). All the reactions show over 90% recovery of o-benzenedisulfonimide that can be reused to prepare the salts. The collateral proofs we performed led us to hypothesize, for this reaction, a free-radical chain mechanism in which hydrogen peroxide is the exclusive hydrogen source in the arenes Ar-H.