Aurore Gref

Functionalisation of saturated hydrocarbons. part x.1 a comparative study of chemical and electrochemical processes (gif and gif-orsay systems) in pyridine in acetone and in pyridine-co-solvent mixtures

Abstract Six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis - and trans -decalin and adamantane) were oxidised by the GifIV system (iron catalyst, oxygen, zinc, carboxylic acid) and its electrochemical equivalent (Gif-Orsay system). Results obtained using various solvents (pyridine, acetone, pyridine-acetone mixtures) were similar for both systems. Total or partial replacement of pyridine with acetone affects the selectivity for secondary positions and lowers the ketone/secondary alcohol ratio. The formation of the same ratio of cis - and trans -decal-9-ol from both cis - and trans -decalin clearly demonstrates that tertiary alcohols result from a mechanism essentially radical in nature.

TOWARDS NEW FERROCENYL LIGANDS FOR ASYMMETRIC CATALYSIS

Some new approaches for asymmetric synthesis of chiral femenyl ligands are described. Many types of ferrocene compounds with planar chirality were prepared through diastereoselective ortholithiation, thanks to a chiral sulfoxide or chiral aced auxiliary. Various mono- and diphosphines may be subsequently generated. In the sulfoxide route, a key intermediate is pure monolithioferrocene. A convenient procedure was set up, involving the isolation of stable tri-n-butylstannyl-femene as a precursor of monolithioferrocene. The species FczPH (Fc = ferrocenyl) and its borane protected derivative allowed to synthesize chiral diphosphines where the usual PPh2 groups are replaced by the PFc2 fragment.

Thioglycosides as Potential Glycosyl Donors in Electrochemical Glycosylation Reactions. Part 1: Their Preparation and Reactivity Toward Simple Alcohols.

Abstract Constant potential electrolysis of several glycosyl donors such as substituted phenyl 2,3,4,6-tetra-O-acetyl, benzoyl or benzyl-1-thio-β-D-gluco or galactopyranosides in dry acetonitrile in the presence of various primary, secondary or tertiary alcohols performed in an undivided cell, gave preferentially β-linked saccharides in moderate to good yields according to the nature of the protective groups on the sugar moiety. 2-Deoxy-2-phthalimido-1-thio-β-D-gluco derivatives gave the β-glucosides selectively in excellent yields. It was found, as expected, that substitution of the phenyl group with methoxy or methyl radicals facilitates the electrochemical glycosylation reaction by lowering the oxidation potentials of the corresponding thioglycosides.

Anodic glycosylation from aryl thioglycosides

Abstract Unprotected aryl thioglucosides undergo electrochemical oxidation in undivided cell at constant moderated potential in the presence of alcohols to give the corresponding glucosides in good yield without any self condensation.

Selective oxidation of saturated hydrocarbons using an electrochemical modification of the gif system.

Abstract The Gif system for selective hydrocarbon oxidation can be carried out replacing the zinc by a cathodic electrochemical reduction; the yields obtained and the selectivities observed are very similar.

On the oxidation of saturated hydrocarbons with H2O2 in the presence of iron(II)-picolinate or iron(II)−1,10 phenanthroline 2-carboxylate.

Abstract A new catalytic system for highly selective oxidation of saturated hydrocarbons into ketones is described. This system is based on the combination of ferrous picolinate (or 1,10 phenanthroline 2-carboxylate) and H2O2 in pyridine solution. Under these conditions cyclohexane gave mainly cyclohexanone (90%, 22–28% yield based on H2O2) and minor amounts of cyclohexanol .

Thioglycosides as Potential Glycosyl Donors in Electrochemical Glycosylation Reactions. Part 2: Their Reactivity Toward Sugar Alcohols.

Abstract Constant potential electrolysis of the glycosyl donors p-methylphenyl 2,3,4,6-tetra-O-benzyl-1-thio-β-D-glucopyranoside (1) and p-methylphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside (4) in dry acetonitrile in the presence of various primary and secondary sugar alcohols, performed in an undivided cell, gave β-linked disaccharide derivatives selectively in good yields. Oxidative coupling of p-methoxyphenyl 2,3,4-tri-O-benzyl-1-thio-β-L-fucopyranoside (2 1) with p-methoxybenzyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-glucopyranoside (16) gave selectively the α-linked disaccharide 22 in good yield.

Asymmetric Synthesis of a Chiral Tetradendate Ligand Based on a Bis[diphenylphosphino-ferrocenyl] Moiety. Electrochemical Behaviour of Free Ligand and its RuII and CuI Complexes

α-Diphenylphosphino carboxaldehyde 4, prepared by asymmetric synthesis, was reacted with ethane diamine to give bisimine bisphosphine 5. Ruthenium(II) complex 6 and copper(I) complex 8 were easily formed and their electrochemical properties studied.

An efficient electrochemical process for the oxidation of saturated hydrocarbons: the Gif–Orsay system

The selective oxidation of saturated hydrocarbons can be carried out using triplet oxygen, pyridine, trifluoroacetic acid, and an iron catalyst in an unicellular electrochemical cell (Gif–Orsay system), cyclododecane, adamantane, and cyclo-octane being oxidised in 17–30 mmolar amounts with improved coulombic yields of up to ∼30% being attainable; oxidation of cyclohexane in 48 mmolar amounts gave cyclohexanone with some cyclohexanol in ∼40% coulombic yield, and similar yields were obtained on a 140–167 mmolar scale (saturated solution of hydrocarbon) with addition of electron transfer reagents and enough water to give two layers (good stirring) and satisfactory conductivity.

[2+2+2] cyclotrimerisation of bisaryl acetylene bearing ferrocenyl units with planar chirality: synthesis of enantiopure conjugated polyferrocene complexes

A new family of highly symmetric and fully conjugated hexaferrocenyl complexes were prepared by a [2 + 2 + 2] cyclotrimerisation reaction of the corresponding alkyne monomers. The preliminary electrochemical behaviour of the new complexes was also evaluated by cyclic voltametry