Hydrodediazoniation of dry arenediazonium o-benzenedisulfonimides with hydrogen peroxide

This report describes the hydrodediazoniation of dry arenediazonium o-benzenedisulfonimides 1 with hydrogen peroxide (2) 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 3 in excellent yields (15 examples, average yield = 93%). All the reactions show over 90% recovery of o-benzenedisulfonimide (4) that can be reused to prepare the salts 1. The collateral proofs we performed led us to hypothesize, for this reaction, a free-radical chain mechanism in which 2 is the exclusive; hydrogen source in the arenes Ar-H3.