Nucleophilic Acyl Substitutions of Anhydrides with Protic Nucleophiles Catalyzed by Amphoteric, Oxomolybdenum Species
journal contributionposted on 18.02.2005, 00:00 by Chien-Tien Chen, Jen-Huang Kuo, Vijay D. Pawar, Yogesh S. Munot, Shieu-Shien Weng, Cheng-Hsiu Ku, Cheng-Yuan Liu
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−MoO2Cl2 adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-α-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the MoO 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−MoOCl2(O2CBut)2 between pivalic anhydride and MoO2Cl2 as the catalyst.
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group VIb oxometallic speciesnucleophilic acyl substitutionbenzoic anhydrideNAS profileoxomolybdenum tetrachloridecontrol NAS reactiondioxomolybdenum dichloridetertoxomolybdenum chloridesadductalkanoic acidpivalic anhydridetrityl methacrylate synthesesProtic Nucleophiles Catalyzedcatalystprotic nucleophilesO 2 CBu tbutylthio esterOxomolybdenum Speciesamphoteric characterMoO 2 Cl 2Nucleophilic Acyl Substitutions