Aryl radicals from hexazadienes and tetrazenes

Abstract

Aryl radicals are produced from both ends of the hexazadienes 1 and 2 and from the tetrazene 3, either thermally or photolytically. They attack aromatic compounds in the nucleus, the yield of biaryl being in the range 40–70%, though it can be made nearly quantitative by using m-dinitrobenzene as an additive. The aryl radicals also oxidize 2-propanol to acetone, the reduction products being the halogenobenzene and 1,2-diacetylhydrazine.Photolysis of 1 goes mainly by way of the tetrazene 3, and this may also be a significant pathway in the thermal reaction. Azodiacetyl is an intermediate in the thermal reaction of 1 with 2-propanol and may be generally so in all its reactions.Radical induced decomposition is believed to be important in the reactions of 1, 2, and 3, and it is probably responsible for the formation of 1-acetyl-1-arylhydrazines, routinely produced in yields of up to 25%.