Heck reactions of ortho-substituted arenediazonium salts: critical observations on electronic effects

An attempted Heck reaction of o-diethylamido phenyldiazonium tetrafluoroborate follows a unique radical-chain protodediazoniation pathway that is triggered by a facile 1,5-[H] shift of the derived aryl radical. Other ortho-substituted salts, irrespective of their redox potentials and structure, behave in the normal way.