title: Nucleophilic acyl substitutions of anhydrides with protic nucleophiles catalyzed by amphoteric, oxomolybdenum species.
abstract: [reaction: see text] Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride-MoO(2)Cl(2) adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-alpha-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl(2)(O(2)CBu(t)())(2) between pivalic anhydride and MoO(2)Cl(2) as the catalyst.
authors.affiliation: Department of Chemistry, National Taiwan Normal University, Taipei 11650, Taiwan. chefv043@scc.ntnu.edu.tw
authors.forename: Chien-Tien
authors.initials: CT
authors.lastname: Chen
authors.forename: Jen-Huang
authors.initials: JH
authors.lastname: Kuo
authors.forename: Vijay D
authors.initials: VD
authors.lastname: Pawar
authors.forename: Yogesh S
authors.initials: YS
authors.lastname: Munot
authors.forename: Shieu-Shien
authors.initials: SS
authors.lastname: Weng
authors.forename: Cheng-Hsiu
authors.initials: CH
authors.lastname: Ku
authors.forename: Cheng-Yuan
authors.initials: CY
authors.lastname: Liu