Transition-Metal-Catalyzed Reactions of Diazo Compounds. 2.1 Addition to Aromatic Molecules: Catalysis of Buchner's Synthesis of Cycloheptatrienes

The addition of carbenes (generated from diazo esters) to aromatic molecules is efficiently catalyzed at room temperature by electron-poor Rh(II) carboxylates [tetrakis(perfluorocarboxylato)dirhodium(II)]. The reaction gives ready access to 1-carbalkoxycyclohepta-2,4,6-trienes (the kinetic nonconjugated isomer) in very good yield. The observed regioselectivities are rationalized in terms of an attack of a highly electrophilic carbenoid species on the aromatic molecule. A competitive reduction of the catalyst simultaneously occurs and is responsible for a slow deactivation of the system. © 1981, American Chemical Society. All rights reserved.