Pierre Y. Chavant

Sc(BINOL)2Li: a new heterobimetallic catalyst for the asymmetric Strecker reaction

Abstract The new chiral heterobimetallic complex Sc(BINOL) 2 Li 1 was prepared and used as a catalyst in the enantioselective addition of a cyanide source (HCN or TMSCN) to several imines. High conversion rates and enantiomeric excesses (e.e.s) as high as 95% were obtained.

An Opportunity for Mg-Catalyzed Grignard-Type Reactions: Direct Coupling of Benzylic Halides with Pinacolborane with 10 mol % of Magnesium

Mg in catalytic amounts as the only metal permits the reductive coupling between benzyl halides and pinacolborane. HBpin acts both as an electrophile and as a reducing agent to regenerate an organomagnesium species in situ. An hydride oxidation mechanism is proposed on the basis of DFT calculations.

A direct and versatile access to alpha,alpha-disubstituted 2-pyrrolidinylmethanols by SmI2-mediated reductive coupling.

Various alpha,alpha-disubstituted 2-pyrrolidinylmethanols are efficiently prepared in a single step from ketones using a SmI2-mediated cross-coupling with 1-pyrroline N-oxide. The N-hydroxy-alpha,alpha-diphenylprolinol is also easily prepared and resolved.

Diastereoselective addition of terminal alkynes to chiral nitrones: asymmetric synthesis of propargylic N-hydroxylamines

Abstract 1,3-Asymmetric induction in the Et2Zn-catalyzed addition of terminal alkynes was studied with nitrones bearing a chiral auxiliary on their nitrogen atom. The obtained propargylic N-hydroxylamines were generally isolated in good yields and with satisfactory to excellent diastereoselectivities.

Application of cooperative iron/copper catalysis to a palladium-free borylation of aryl bromides with pinacolborane.

A new cooperative copper/iron catalysis for the borylation of various aryl bromides with pinacolborane, at -10 °C, is reported. Use of the toxic, precious metal Pd is avoided. The mechanism of the protodebromination side reaction is discussed.

Self-organization of ligands in multi-component titanium catalysts for the enantioselective ene reaction of glyoxylates

Abstract Addition of conformationally flexible biphenols to ( R )-BINOL–Ti(O i Pr) 2 , forms a new catalytic species with which ee s are as high as 97.3% in the hetero-ene reaction of n -butyl glyoxylate to α-methyl styrene.

Iron, cobalt and nickel boride as precursor of heterogeneous oxazaborolidine catalysts

Abstract Heterogeneous 1,3,2-oxazaborolidine catalysts FeB 1.8–0.1 (oxaza) 0.1 , CoB 2−0.1 (oxaza) 0.1 and NiB 2−0.1 (oxaza) 0.1 were prepared by reacting iron, cobalt and nickel boride with (1 S , 2 R )-(+)-2-amino-1,2-diphenylethanol. Over these catalysts, acetophenone can be reduced with high enantioselectivity (ee=97%) by using borane N , N -diethylaniline complex. The capacity to be used again depends on the metal. The detrimental effect of residual water in the metallic salt before reduction, on the enantioselective properties of the catalyst is demonstrated. The formation of the oxazaborolidine ring is substantiated by IR spectroscopy.

Theoretical approach and first examples of N-acyl-thioformamides as dienophiles in the Diels–Alder reaction

ab initio Calculations as well as experimental results show that the C = S bond of a thioamide can act as a dienophile in the Diels–Alder reaction provided that the nitrogen atom is substituted by π-acceptor groups.

Addition of functional vinylzinc reagents to nitrones: synthesis of (E)-N-allylhydroxylamines and their rearrangement into (E)-O-allylhydroxylamines

The vinylzinc reagents derived from hydrozirconation of alkynes and transmetallation add readily to nitrones to yield pure (E)-N-allylhydroxylamines; some of these rearrange into O-allylhydroxylamines.

Total synthesis of bernumicine and bernumidine, two alkaloids from Berberis nummularia †

Bernumicine and bernumidine are two alkaloids extracted from Berberis nummularia. Their total synthesis has been completed and it has been shown that the configuration of the stereogenic carbon of both is (R).