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 250º/0.002-0.40 mm. In all cases, carbene insertion into the adjacent CH bond (Bamford- Stevens insertion) occurs, either exclusively or predominantly, with up to 35% 1, 5 CH insertion in the alkoxy side chain to form peri-fused tricyclic heterocycles.
