title: Rhodium(III)-Catalyzed [4+1] Annulation of Aromatic and Vinylic Carboxylic Acids with Allenes: An Efficient Method Towards Vinyl-Substituted Phthalides and 2-Furanones.
abstract: A highly regio- and stereoselective synthesis of 3,3-disubstituted phthalides from aryl carboxylic acids and allenes using a rhodium(III) catalyst has been demonstrated. The reaction features broad functional group tolerance and provides a simple and straightforward route to the synthesis of various 3-vinyl-substituted phthalides. Furthermore, the catalytic reaction can also be applied to the synthesis of biologically active 5-vinyl-substituted 2-furanones from α,β-unsaturated carboxylic acids and allenes. The reactions proceed through a carboxylate-assisted ortho-CH activation and [4+1] annulation. The preliminary mechanistic studies suggest that a CH cleavage is the rate-determining step.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan).
authors.forename: Parthasarathy
authors.initials: P
authors.lastname: Gandeepan
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan).
authors.forename: Pachaiyappan
authors.initials: P
authors.lastname: Rajamalli
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013 (Taiwan). chcheng@mx.nthu.edu.tw.
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Cheng
keywords: CH activation; allenes; annulation; carboxylic acids; reaction mechanisms; rhodium