Intramolecular Anodic Olefin Coupling Reactions and the Use of Electron-Rich Aryl Rings(1)

The utility of intramolecular anodic olefin coupling reactions involving electron-rich aromatic rings for constructing fused, bicyclic ring skeletons has been examined. Reactions involving alkoxy-substituted phenyl rings were found to benefit strongly from a 3-methoxy substituent on the phenyl ring. Although overoxidation of the bicyclic product was observed in these reactions, this problem could be minimized with the use of controlled potential electrolysis conditions when a monomethoxy phenyl ring was used and avoided entirely with the use of a vinyl sulfide moiety as the initiator when a more electron-rich phenyl ring was used. Reactions involving 4-alkoxy-substituted phenyl rings as substrates did not lead to good yields of fused products. Furan rings were found to be excellent coupling partners for the reactions and afforded products having fused, bicyclic furan ring skeletons. Cyclizations involving furans were shown to be compatible with the formation of both six- and seven-membered rings, the generation of a quaternary carbon, and the use of a variety of electron-rich olefins as the other coupling partner. It appears that the furan can serve as either the initiating group or the terminating group for the cyclizations. Finally, the reactions were shown to be compatible with the use of a pyrrole ring as one of the participants.