Regioselectivity in the intramolecular substitution reactions of electrochemically and photochemically generated aryl radicals with adjacent pyridine and quinoline rings. A comparison between these reactions and related processes involving tributyltin hydride

Cleavage of the carbon-halogen bond in 1-(3-pyridinyl)- and 1-(3-quinolinyl)-5-(1-halogenophenyl)tetrazoles leads to a sigma-radical which undergoes a cyclization reaction onto the adjacent heterocyclic ring. Bond cleavage is effected both by electrochemical reduction and by photolysis. Yields of cyclized products formed in the two types of reaction are compared. The relative advantages of the electrochemical generation of an aryl a-radical from aryl halides over reaction of the same substrate with tributyltin hydride and a radical initiator are discussed.