Paul Lhoste

An easy palladium-catalyzed access to 2-alkylidene-1,4-benzodioxanes

Abstract Palladium-catalyzed cyclization of benzene-1,2-diol with various propargylic carbonates led to 2-alkylidene-1,4-benzodioxanes in excellent chemical yields. Diphosphines such as dppb, dpppe or dpph, and monophosphines are the best ligands.

Rhodium(I)–sulfonated-bdpp catalysed asymmetric hydrogenation of imines in aqueous–organic two-phase solvent systems

The imines ArC(Me)NCH2Ph (Ar = Ph, 2-MeO-C6H4, 3-MeO-C6H4, 4-MeO-C6H4) are hydrogenated to the corresponding amines with extremely high enantioselectivities up to 96% under very mild conditions, using rhodium complexes associated with sulfonated bdpp.

One-pot preparation of chiral 2-vinyl-1,4-benzodioxane

2-Vinyl-1,4-benzodioxane was obtained with e.e. up to 45 % by condensation of catechol and (Z)-2-butene-1,4-diylbis(methylcarbonate) in the presence of a catalytic amount of palladium(0) in association with chiral ligand such as BINAP.

Asymmetric palladium(0)-mediated synthesis of 2-vinylchroman

Abstract Optically active 2-vinylchroman was synthesized from the corresponding hydroxy allylic carbonate by palladium-catalyzed cyclization in the presence of various chiral ligands. Enantioselectivity of up to 53% was obtained using NMDPP as the chiral phosphine.

Palladium(O)-catalyzed alkylation of thiols

Abstract Palladium(O)-catalyzed alkylation of various allylic carbonates by aromatic thiols allowed the easy preparation of various allylic aryl sulphides in quite good yields. The reaction was regioselective with substitution at the less hindered side of the π-allyl system whatever the temperature of the reaction, and was diastereoselective with net retention of configuration.

Palladium(0)-catalysed synthesis of cis- and trans-linalyl oxides

Abstract Linalyl oxides are obtained from (Z)- or (E)-6,7-dihydroxy-3,7-dimethyl-oct-2-enyl carbonate in the presence of Pd2(dba)3 in association with various ligands.

HIGHLY REGIO AND CHEMOSELECTIVE RING OPENING OF EPOXIDES WITH TRIMETHYLSILYL AZIDE IN THE PRESENCE OF ALUMINIUM ISOPROPOXIDE AND TITANIUM ISOPROPOXIDE

Abstract The ring-opening of functionalized epoxides with trimethylsilyl azide in the presence of a catalytic amount of Ti(O- i -Pr) 4 or Al(O- i -Pr) 3 is described. The reaction is stereospecific and highly regiospecific, leading generally to the formation of the carbon-azido bond on the less substituted carbon. The mechanism of this reaction is also discussed.

Palladium(0)-catalyzed asymmetric synthesis of 2-vinylmorpholine and 2-vinylpiperazine. Influence of the biscarbonate structure on the enantioselectivity

Abstract Palladium-catalyzed cyclization of N,N-bis(p-tolylsulfonyl)-o-phenylenediamine 2b and 2-[(2,4,6-trimethylphenyl)sulfonyl]aminophenol 2c with three allylic biscarbonates 1a–c gave quite different enantioselectivities. This indicates that the cyclization processes do not have a common intermediate, as in the case of benzene-1,2-diol.

Pd-Catalyzed annulation of benzene-1,2-diol and propargylic carbonates: a new example of asymmetric catalysis

The palladium-catalyzed cyclization of benzene-1,2-diol with various secondary propargylic carbonates in the presence of (R)-Binap as the chiral ligand afforded the corresponding 2,3-dihydrobenzo-1,4-dioxin derivatives in quite good yields, and also in enantioselectivities of up to 93%. The assumed enantioselective step is the protonation of a palladium–carbene intermediate.

PALLADIUM(0)-CATALYZED ASYMMETRIC SYNTHESIS OF 1,2,3,4-TETRAHYDRO-2-VINYLQUINOXALINES

Reaction of (Z)-1,2-bis(methoxycarbonyloxy)but-2-ene (2) with various N,N-bis(arylsulfonyl)-o-phenylenediamines 1 was catalyzed by a palladium complex associated with chiral ligands to give optically active 1,4-bis(arylsulfonyl)-1,2,3,4-tetrahydro-2-vinylquinoxalines 3 with up to 62% ee. The use of (S)-MeOBIPHEP as the chiral ligand and N,N-bis(p-tolylsulfonyl)-o-phenylenediamine (1i) as the nucleophile led to the highest ee at 25 °C, regardless of the solvent used. The enantioselectivity of the cyclization is strongly affected by the nature of the substituents at the nitrogen atom.