title: Easy access to esters with a benzylic quaternary carbon center from diallyl malonates by palladium-catalyzed decarboxylative allylation.
abstract: Diallyl 2-alkyl-2-arylmalonates underwent palladium-catalyzed decarboxylative allylation quickly under mild conditions. In contrast, no reaction took place with diallyl 2,2-dialkylmalonates under the same conditions. Electron-donating phosphine ligands were found to be vital for this reaction. Most of the solvents used did not affect the catalytic cycle. Catalysis in [bmim][BF4], a well-known ionic liquid, was inhibited as a result of formation of a hydrogen bond between a carboxylate anion and a [bmim]+ cation; however, the reaction in [bdmim][BF4], in which the acidic proton of [bmim][BF4] was replaced with a methyl group, proceeded smoothly. The catalytic mechanism was investigated using a tetradeuterated substrate and an enzymatically synthesized enantio-enriched allyl methyl 2-methyl-2-phenylmalonate. Even the electron-deficient phosphite ligand was found to be active for catalysis of diallyl 2-methyl-2-(2- or 4-nitrophenyl)malonates.
authors.affiliation: Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Imao
authors.forename: Akihiro
authors.initials: A
authors.lastname: Itoi
authors.forename: Asako
authors.initials: A
authors.lastname: Yamazaki
authors.forename: Masamichi
authors.initials: M
authors.lastname: Shirakura
authors.forename: Ryota
authors.initials: R
authors.lastname: Ohtoshi
authors.forename: Kenta
authors.initials: K
authors.lastname: Ogata
authors.forename: Yohki
authors.initials: Y
authors.lastname: Ohmori
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ohta
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Ito