Synthetic applications of intramolecular insertion in arylcarbenes. VII. Aryl-substituted benzocycloalkenylidenes

Abstract

A series of benzo-fused cyclic carbenes, bearing suitably located alkoxy substituents in the phenyl ring, has been generated in the gas phase and pyrolysed at 250�/0.002-0.40 mm. In all cases, carbene insertion into the adjacent C-H bond (Bamford-Stevens insertion) occurs, either exclusively or predominantly, with up to 35% 1,5 C-H insertion in the alkoxy side chain to form peri-fused tricyclic heterocycles. These results are rationalized in terms of geometrical and electronic effects.