title: Mechanism of scandium ion catalyzed Diels-Alder reaction of anthracenes with methyl vinyl ketone.
abstract: Rates of Diels-Alder cycloadditions of anthracenes with methyl vinyl ketone (MVK) are accelerated significantly by the presence of scandium triflate [Sc(OTf)3]. Sc(OTf)3 also promotes photoinduced electron-transfer reactions from various electron donors to MVK significantly. Comparison of the promoting effect of Sc(OTf)3 in photoinduced electron-transfer reactions of MVK with the catalytic effect of Sc(OTf)3 in the Diels-Alder reaction of 9,10-dimethylanthracene with MVK has revealed that the MVK-Sc(OTf)3 complex is a reactive intermediate in both the Diels-Alder and photoinduced electron-transfer reactions. The observed second-order rate constants of the Sc(OTf)3-catalyzed Diels-Alder reactions of anthracenes with MVK are by far larger than those expected from the observed linear Gibbs energy relation for the Diels-Alder reactions of anthracenes with stronger electron acceptors than MVK, which are known to proceed via electron transfer. This indicates that the Sc(OTf)3-catalyzed Diels-Alder reactions of anthracenes with MVK does not proceed via an electron-transfer process from anthracences to the MVK-Sc(OTf)3 complex.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Corporation (JST), Suita, Osaka 565-0871, Japan. fukuzumi@chem.eng.osaka-u.ac.jp
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Junpei
authors.initials: J
authors.lastname: Yuasa
authors.forename: Toshio
authors.initials: T
authors.lastname: Miyagawa
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Suenobu
mesh_terms: D000873:Anthracenes / Q000737:chemistry*; D002074:Butanones / Q000737:chemistry*; D002384:Catalysis; D016337:RNA, Catalytic / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D012538:Scandium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000873:Anthracenes; D002074:Butanones; C518747:Diels-Alder ribozyme; D016337:RNA, Catalytic; C057920:3-buten-2-one; D012538:Scandium