Jacques Muzart

Synthesis of unsaturated carbonyl compounds via a chromium-mediated allylic oxidation by 70% tert.butylhydroperoxide

Abstract Alkenes were converted into α,β-unsaturated carbonyl compounds using excess of tert.butylhydroperoxide and catalytic amounts of chromium VI oxide at room temperature. Fair yields and conversions were obtained from Δ 5 -steroids while allylic oxidation of acyclic alkenes was less efficient. Epoxidation of the double bond, sometimes observed, remained a minor reaction pathway.

Practical chromiumVI oxide-catalyzed benzylic oxidations using 70% tert-butylhydroperoxide

Abstract In using 70% t.BuOOH and catalytic amounts of chromic anhydride, benzylic methylene groups are oxidized at room temperature to carbonyl functions in fair yields.

ChromiumVI complex catalyzed benzylic oxidations in the presence of tert.butyl hydroperoxide

Abstract In using t.BuOOH and a small quantity of 2,4-dimethylpentane-2,4-diol cyclic chromate, benzylic methylene groups are oxidised into carbonyl functions ; t.butylperoxy compounds are postulated as intermediates.

Enantioselective allylic oxidation in the presence of the Cu(I)Cu(II)-proline catalytic system

Abstract Optically active allylic esters have been obtained with ees up to 54% by acyloxylation of the corresponding alkenes with t-BuOOC(O)Ph or t-BuOOH + RCOOH in the presence of catalytic amounts of copper compounds and homochiral aminoacids ((S)- and (R)-prolines and their structural analogs). The influence of the nature of the alkene and acyl groups, the oxidant, solvent and chiral promotor on the enantioselectivity has been studied. A key role of CuL2∗ ( L ∗ = aminoacid ) in the enantioselective catalysis is suspected.

Copper(I)-Catalyzed Synthesis of Substituted 2-Mercapto Benzimidazoles

An efficient method for the preparation of various substituted 2-mercapto benzimidazoles from their corresponding thioureas has been developed. S-alkylation of thioureas followed by Cu-catalyzed intramolecular N-arylation furnished substituted 2-mercapto benzimidazoles in high yields and short reaction times. Furthermore, 2-mercapto benzimidazoles substituted with a p-methoxybenzyl group allowed access to benzimidazole thiones.

ASYMMETRIC PROTONATION OF ENOLIC SPECIES : DRAMATIC INCREASE IN THE SELECTIVITY WITH TEMPERATURE AND UNEXPECTED EYRING DIAGRAM

Abstract The palladium-induced cleavage of β-ketosters and enol carbonates derived from α-alkylated 1-indanones and 1-tetralones in the presence of (+)- endo -2-hydroxy- endo -3-aminobornane led to ( R )- α -alkylated indanones and tetralones with a large increase in the enantioselectiviy (up to 38–40%) when the reaction temperature was raised from 21 to 45–70°C. Thus, enantiopure 2-methyl-1-indanone was obtained at 52°C. More than one inversion temperature has appeared in plotting the corresponding Eyring diagrams.

Palladium(II)-mediated oxidation of alcohols using 1,2-dichloroethane as Pd(O) reoxidant

Abstract The oxidation of primary and secondary, saturated, allylic or benzylic, alcohols is carried out in 1,2-dichloroethane at reflux using catalytic amounts of both PdCl 2 and Adogen 464 in the presence of an excess of sodium carbonate. High selectivities are obtained from saturated and benzylic, secondary alcohols. Primary alcohols afford mixtures of aldehydes and esters. The migration of the double bond of α,β-unsaturated alcohols is a competing reaction. It is clearly shown that 1,2-dichloroethane reoxidizes the Pd(O) species.

Palladium-Catalyzed Allylic Acyloxylation of Terminal Alkenes in the Presence of a Base

The efficiency and the selectivity of the Pd-catalyzed oxidation, in carboxylic acids, of terminal alkenes are strongly improved in the presence of a base. The methodology is particularly well adapted for the oxidation of homoallylic alcohols, for which the resulting acyloxylated products are obtained selectively as E-isomers in fair to good yields.

Palladium nanoparticles obtained from palladium salts and tributylamine in molten tetrabutylammonium bromide: their use for hydrogenolysis-free hydrogenation of olefins

Carbon-carbon double bonds have been selectively hydrogenated at room temperature in the presence of benzyloxy groups using an atmospheric pressure of hydrogen, toluene or [bmim]PF6 as the solvent and palladium nanoparticles stabilized with tetrabutylammonium bromide. The system [bmim]PF6/palladium nanoparticles can be recycled without noticeable decrease of activity.

Palladium-Catalyzed Dehydrogenative Coupling of Furans with Styrenes

Under palladium(II)-catalyzed and oxidative conditions, the coupling of furans with styrenes leads to the formation of Heck-type products in medium to good yields. The reaction is highly regio- and stereoselective, giving trans-olefins predominantly.