Jacqueline Collin

Ring opening reactions of epoxides catalyzed by samarium iodides

Abstract Sml2(THF)2 catalyzes the ring opening of epoxides by trimethylsilylazide, trimethylsilylcyanide and primary and secondary amines. High regioselectivities are observed in specific cases.

MUKAIYAMA ALDOL AND MICHAEL REACTIONS CATALYZED BY LANTHANIDE IODIDES

Abstract Samarium diiodide is an efficient catalyst precursor which allows the formation of condensation products between various carbonyl compounds and ketene silyl acetals or enoxysilanes. With α,β-unsaturated carbonyl compounds, 1,2- or 1,4-additions are observed according to the structure of the substrate. α,β-Unsaturated ketones yield to enoxysilanes by selective Michael additions. Aldol poducts are isolated as silyl ethers. The mechanisms of the reactions are discussed.

Well-defined and easily accessible yttrium complexes for enantioselective cyclisation of amines tethered to 1,2-di-substituted alkenes

A straightforward in situ preparation of new chiral amido alkyl ate yttrium complexes is described. They catalysed the enantioselective cyclisation of 1,2-dialkyl-substituted aminopentenes in up to 77% ee, a significant value for this challenging transformation. Complex [(R)-L(0)][Y(CH(2)TMS)(2).Li(THF)(4)] undergoes C-H bond activation resulting in the formation of an original dimeric heterobimetallic yttrium complex which also acts as an active precatalyst.

Convenient method for the rapid generation of highly active and enantioselective yttrium catalysts for asymmetric hydroamination

A facile method for the preparation of highly active and enantioselective yttrium precatalysts for asymmetric hydroamination of gem-disubstituted aminoalkenes, from the combination of YCl(3) or YCl(3)(THF)(3.5) with ligand (R)- and n-BuLi is described.

Imino-Diels–Alder and imino-aldol reactions catalyzed by samarium diiodide

Abstract In the presence of a catalytic amount of samarium diiodide in methylene chloride, aromatic imines react with Danishefsky diene to form tetrahydropyridine-4-ones in high yields. Under the same conditions, various imino-aldol reactions afford β-amino esters or β-amino ketones.

Catalytic, enantioselective intramolecular hydroamination of primary amines tethered to di- and trisubstituted alkenes.

The in situ preparation of chiral amido alkyl ate yttrium complexes from an array of chiral N-benzyl-like-substituted binaphthyldiamines is reported. These chiral heteroleptic complexes are shown to be efficient catalysts for the enantioselective intramolecular hydroamination of primary amines tethered to sterically demanding alkenes at high reaction temperatures. Fine tuning of their chiral environment allowed up to 77% ee to be reached for the cyclization of aminoalkenes bearing 1,2-dialkyl-substituted carbon-carbon double bonds. These chiral complexes also demonstrate the ability to promote the cyclization of amine-tethered trisubstituted alkenes in up to 55% ee, as the first report of the formation of enantioenriched quaternary centers by an hydroamination reaction.

Diiodosamarium an excellent catalyst precursor for Aldolisation and Michael reactions.

Abstract SmI 2 is the precursor of efficient catalysts for the aldolisation reactions of aldehydes and ketones with enol silanes. α,β-unsaturated ketones give 1,4-addidtions selectively.

Synthesis and reactivity of benzylic and allylic samarium compounds

Abstract Benzyl and allyl samarium species are prepared by reaction of benzylic or allylic chlorides with SmCp2. They present a wide scope of reactivity towards aldehydes, ketones and acid chlorides.

Lanthanide iodides, a new family of efficient Lewis acid catalysts

Abstract Samarium diiodide and other lanthanide iodides are very efficient Lewis acid catalysts for numerous reactions such as Mukaiyama aldol and Michael reactions, preparation of enoxysilanes, cycloaddition reactions and ring opening of oxiranes by silylated nucleophiles or amines. Activities and selectivities of catalysts vary with the nature of the metal and the ligands for some reactions. Lanthanide iodides coordinated by a cyclopentadienyl ligand with an asymmetric center and an ether function on a pendant chain have been characterized and tested for catalysis: low enantioselectivities are observed for complexes with intramolecular coordination.

SYNTHESIS OF LANTHANIDE COMPLEXES COORDINATED BY AN ASYMMETRIC CYCLOPENTADIENYL LIGAND

Abstract The synthesis and characterization of bis- and monocyclopentadienyl lanthanide [(S)-Cp′]2Lnl (Ln  Sm, 3; Ln  La, 4) and (S)-Cp′Lnl2(THF)R, (Ln  Sm, n = 3, 5; Ln  La, n = 2, 6) coordinated by an asymmetric cyclopentadienyl ligand (Cp′ = C5H2CH2CH(CH3)OCH2Ph) have been carried out. Variable-temperature NMR study of compounds 3 and 4 reveals a fluxional process in solution. The X-ray crystal structure analysis of 3 shows a bent metallocene structure with intramolecular coordination to the oxygen atoms of the side chains of both cyclopentadienyl ligands. For monocyclopentadienyl complexes, intramolecular coordination is observed only for the lanthanum complex 6. All compounds exhibit activity for the catalysis of Diels-Alder reactions.