Oxyfunctionalization of unactivated C-H bonds in triterpenoids with tert-butylhydroperoxide catalyzed by meso-5,10,15,20-tetramesitylporphyrinate osmium(II) carbonyl complex.
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.
Ogawa
Shoujiro
S
Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajousui, Setagaya-ku, Tokyo 156-8550, Japan.
Wakatsuki
Yasuo
Y
Makino
Mitsuko
M
Fujimoto
Yasuo
Y
Yasukawa
Ken
K
Kikuchi
Takashi
T
Ukiya
Motohiko
M
Akihisa
Toshihiro
T
Iida
Takashi
T
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*
D056831:Coordination Complexes; D014315:Triterpenes; D009992:Osmium; D020122:tert-Butylhydroperoxide