B. Waegell

Binuclear copper complex model of tyrosinase

The synthesis is reported of a binuclear copper(I) complex 2 which exhibits the catalytic phenolase and catecholase activity of tyrosinase.

Epoxidation with molecular oxygen in the presence of PdCl (NO2) (CH3CN)2

Abstract Several mono or non conjugated diolefins are submitted to the action of oxygen in presence of catalytic amounts of PdCl (NO2) (CH3CN)2. Depending on the olefin structures methylketones or epoxides are obtained.

Synthesis of ambergris fragrance chemicals from sclareol, involving palladium catalysed key steps

Abstract Ambraoxide, Ambrox ®, methylambraoxide and ambracetal are synthetised via key steps involving respectively a palladium acetate catalysed elimination and a PdCl 2 (CH 3 CN) 2 catalysed isomerisation of the mixture of sclareol and episclareol acetates.

A novel approach toward the prediction of the glass transition temperature: Application of the EVM model, a designer QSPR equation for the prediction of acrylate and methacrylate polymers

We describe an original QSPR model called the EVM model (Energy, Volume, Mass) to calculate the glass transition temperature (Tg) of aliphatic acrylate and methacrylate homopolymers using classical molecular mechanics and dynamics. The latter was used to calculate an energy density function related to the cylindrical volume of a 20 monomer unit polymer segment (TSSV, Total Space around a Standard deviation Volume). We then calculated the Tg as a function of this density function and the repeat unit molecular weight, although no interchain interactions were taken into account. For linear and branched aliphatic acrylate and methacrylate polymers, the standard deviation from linear regression was 12 K, and the r2 was 0.96. The model allows calculation of the Tg with an average absolute error of error of 10% for linear and branched derivatives not included in the original linear regression analysis. The results obtained with the EVM model are compared with those obtained with Biceranos model.

A short and efficient synthesis of (−)-Ambrox® from (−)-sclareol using a ruthenium oxide catalyzed key step.

Abstract (−)-Ambrox® 5 has been synthesized in 3 steps from natural (−)-sclareol 1 . Depending on the reoxidizing agents and the reaction conditions used in the ruthenium oxide catalysed key step, overall yields of 79% (NaIO 4 /RuO 4 ) or 48% (Ca(OCl) 2/ RuO 4 -) were observed.

Ruthenium-catalyzed CH bond activation oxidation of bridged bicyclic and tricyclic alkanes

Abstract Catalytic oxidation (hydroxylation) with RuO 4 generated in situ occurs preferentially in tertiary position with retention of configuration on various bicyclic or tricyclic alcanes.

Synthesis of water-soluble ligands with a quaternary ammonium salt: use in bdphasic palladium-catalyzed telomerisation of butadiene and isoprene

Abstract Water-soluble ligands are synthesized by quaternization of tertiary aminophosphine with either hydrochloric acid or methyl iodide. The use of these ligands in the biphasic palladium-catalyzed telomerisation of butadiene, produces 1-methoxy-2,7-octadiene with 78% selectivity and conversions ranging from 52 to 79%. Conversion and selectivity are little altered on catalyst recycling. Telomerisation of isoprene is somewhat less satisfactory, with a conversion not higher than 52%.

Competition between catalytic epoxidation and oxidative cleavage of trans-stilbene by ruthenium complexes associated with bidentate ligands

Abstract Bidentate ligands featuring two different nitrogen heterocycles (pyridine, oxazoline, oxazolidine and thiophene) directly linked together or separated by a spacer, have been prepared and used as ruthenium ligands to epoxidize trans -stilbene and to study the competition between this reaction and oxidative cleavage of the double bond.

Nickel-catalyzed oligomerization of functionalized conjugated dienes

Abstract The cyclodimerization of several functionalized dienes with nickel(0) catalysts has been studied. When a functional group, such as a methoxycarbonyl or a trimethylsiloxy group, is bonded directly to the terminal carbon of the diene grouping, a completely regio- and stereo-selective dimerization is observed and trans -1,2-disubstituted cycloocta-3,7-dienes are formed in good yields (80–90%). When one carbon atom separates the functional group from the diene group, the yield drops significantly (to 30%), and the stereoselectivity and the clean nature of the reaction are completely lost. The effect of the nature of the nickel catalyst and the influence of the reductive organoaluminum species are discussed. The particular structure and the stereochemical features of the cyclooctadiene derivatives allow a better understanding of the various steps involved in the catalytic process. A reaction mechanism is proposed.

Synthesis of norambracetal: A new ambergris derivative.

Abstract We describe the synthesis of norambracetal 14 from sclareol 1 using γ -homobicyclofarnesilic aldehyde1O as a key intermediate.