Intramolecular Addition of Aryl Radicals to Carbon-Nitrogen Double Bonds.

Abstract Cyclisation of radicals 6a,b is highly regioselective towards a 5-exo process; 6-endo ring closure is a minor route and their ratio depends on the substituents. No ring expansion of the five-membered radical intermediates 7a,b was observed. Radicals 27a,b give rise to 5-exo cyclisation regiospecifically. A competitive 1,5-hydrogen shift leading to imidoyl radicals was noticed. An analogous behaviour is also exhibited by vinyl radicals when allowed to add to carbon-nitrogen double bonds.