Ansari et al.

, (1977)

Regiospecific oxidation of unsaturated fatty esters with palladium(II) chloride/p-benzoquinone: a sonochemical approach

Jie, Marcel S. F. Lie Ken,Lam, C. K.

, p. 55 - 62 (1996)

Oxidation of unsaturated fatty esters to the corresponding oxo derivatives was accomplished in moderate to high yields when the substrates were treated with palladium(II) chloride and p-benzoquinone in aqueous tetrahydrofuran (THF/H2O, 4:1 v/v) under ultrasound (20 kHz).Methyl 10-undecanoate furnished methyl 10-oxoundecanoate in 92percent yield.Methyl oleate and trans-2-hexadecenoate furnished methyl 9(10)-oxostearate (65percent) and methyl 3-oxohexadecanoate (41percent) respectively.Unsaturated fatty esters with a terminal double bond were more readily oxidized than those containing an internal double bond.Methyl trans-3,12-tridecadienoate gave only methyl 12-oxo-trans-3-tridecenoate (86percent), while a cyclopentenoic fatty ester (methyl chaulmoograte) furnished a mixture of positional oxo-isomers: viz. methyl 1-oxocyclopentane-2-tridecanoate and 1-oxocyclopentane-3-tridecanoate (51.5percent total).Oxidation of methyl 12-hydroxy-, 12-azido-, 12-chloro- and 12-oxo-cis-9-octadecanoate furnished the corresponding 9-oxo-derivatives only.Methyl iso-ricinoleate (methyl 9-hydroxy-cis-12-octadecenoate) gave exclusively methyl 9-hydroxy-12-oxostearate.Without ultrasonication the same oxidation reactions at room temperature furnished low yields (30percent) of the corresponding oxo derivatives after prolonged stirring at room temperature.Aqueous THF is a superior solvent system than the commonly used aqueous N,N-dimethylformmaide (DMF). - Keywords: Aqueous THF; p-Benzoquinone; Oxidation; Oxo fatty esters; Palladium(II) chloride; Ultrasound; Unsaturated fatty esters; Wacker reaction

Evocarpin, a new alkaloid from Evodia rutaecarpa

Tschesche,Werner

, p. 1873 - 1881 (1967)

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Non-volatile floral oils of Diascia spp. (Scrophulariaceae)

Dumri, Kanchana,Seipold, Lars,Schmidt, Juergen,Gerlach, Guenter,Doetterl, Stefan,Ellis, Allan G.,Wessjohann, Ludger A.

, p. 1372 - 1383 (2008/09/20)

The floral oils of Diascia purpurea, Diascia vigilis, Diascia cordata, Diascia megathura, Diascia integerrima and Diascia barberae (Scrophulariaceae) were selectively collected from trichome elaiophores. The derivatized floral oils were analyzed by gas chromatography-mass spectrometry (GC-MS), whilst the underivatized samples were analysed by electrospray ionization mass spectrometry (ESI-MS) and Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS). The most common constituents of the floral oils investigated are partially acetylated acylglycerols of (3R)-acetoxy fatty acids (C14, C16, and C18), as was proven with non-racemic synthetic reference samples. The importance of these oils for Rediviva bees is discussed in a co-evolutionary context.

Enantioselective Hydrogenation of β-Keto Esters using Chiral Diphosphine-Ruthenium Complexes: Optimization for Academic and Industrial Purposes and Synthetic Applications

Ratovelomanana-Vidal,Girard,Touati,Tranchier,Ben Hassine,Genet

, p. 261 - 274 (2007/10/03)

Enantioselective hydrogenation using chiral complexes between atropisomeric diphosphines and ruthenium is a powerful tool for producing chiral compounds. Using a simple and straightforward in situ catalyst preparation, the conditions were optimized using molecular hydrogen for both academic and industrial purposes. This led to the best conditions and the lowest catalytic ratio required for the pressure used. Hydrogenation of various β-keto esters was efficiently performed at atmospheric and higher pressures, leading to the use of very low catalyst-substrate ratios up to 1/20,000. Asymmetric hydrogenations were used in key-steps towards the total synthesis of corynomycolic acid, Duloxetine and Fluoxetine.