title: Oxyfunctionalization of unactivated C-H bonds in triterpenoids with tert-butylhydroperoxide catalyzed by meso-5,10,15,20-tetramesitylporphyrinate osmium(II) carbonyl complex.
abstract: A system consisting of meso-5,10,15,20-tetramesitylporphyrinate osmium(II) carbonyl complex [Os(TMP)CO] as a precatalyst and tert-butylhydroperoxide (TBHP) as an oxygen donor is shown to be an efficient, regioselective oxidant system for the allylic oxidation, ketonization and hydroxylation of unactivated C-H bonds in a series of the peracetate derivatives of penta- and tetracyclic triterpenoids. Treatment of the substrates with this oxidant system afforded a variety of novel or scarce oxygenated derivatives in one-step. Structures of the isolated components, after chromatographic separation, were determined by spectroscopic methods including GC-MS and shift-correlated 2D-NMR techniques. Factors governing the regioselectivity and the possible mechanism for the oxyfunctionalization of the unactivated carbons are also discussed.
authors.affiliation: Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajousui, Setagaya-ku, Tokyo 156-8550, Japan.
authors.forename: Shoujiro
authors.initials: S
authors.lastname: Ogawa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Wakatsuki
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Makino
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Ken
authors.initials: K
authors.lastname: Yasukawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Motohiko
authors.initials: M
authors.lastname: Ukiya
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Akihisa
authors.forename: Takashi
authors.initials: T
authors.lastname: Iida
mesh_terms: D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D009992:Osmium / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D014315:Triterpenes / Q000737:chemistry*; D020122:tert-Butylhydroperoxide / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D014315:Triterpenes; D009992:Osmium; D020122:tert-Butylhydroperoxide