Tandem CDC Processes

During recent years, great progress has been made on the CDC reaction of benzylic C-H bonds adjacent to nitrogen or ojgrgen atoms. The formation of iminium or oxonium ions plays an important role in these coupling 

Xanthene and acridane derivatives are pharmaceutically active compounds, as well as natural compounds, and their synthesis has attracted much attention. Recently, Klussmann and co-workers reported the oxidative coupling of xanthene and other activated benzylic compounds with carbon-based nucleophiles such as ketones. The reaction proceeded smoothly under 

Cross-Dehydrogenative-Coupling Reactions Involving Allyl, Benzyl and Alkyl C-H Bonds 99 

3-Dicarbonyl compounds are able to co-ordinate to various Lewis acids to form nucleophiles and have been employed in various transformations. Gong and co-workers developed an enantioselective oxidative cross-coupling reaction of 3-indolylmethyl C-H bonds with 1,3-dicarbonyls using a chiral Lewis acid catalyst. The combination of the Lewis acid Cu(OTf)2 with a chiral bis(oxazoline) ligand exhibited the best reactivity and enantioselec-tivity. The reaction proceeded smoothly at 0 °C using DDQ as the oxidant 

Shi and co-workers disclosed the use of DDQ for the direct arylation of diphenylmethane derivatives. A variety of electron-rich aromatic substrates were successfully coupled with the benzylic C-H bonds of diphenylmethane catalyzed by FeCl2, and gave the corresponding products in good-to-excellent yields. The methojy group of aromatic substrates played an important role in regioselectivity. Orthoester-, acetojq -, carboxy-, carbonyl-, and 

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