Jean-Pierre Barnier

The cyclopropanation of silyl enol ethers of cisoid or labile α-ethylenic ketones. A general and rapid route to cyclobutanones and cyclopentanones.

Aus den ungesattigten Ketonen (Ia) und (Ib) entstehen die Silyl-Enolather (IIa) und (IIb), die selektiv nach Simmons-Smith (Methylenjodid-Zn/Ag) zu den Cyclopropanen (III) umgesetzt werden.

REACTION OF DIHYDROSILANES WITH ETHYL DIAZOACETATE : SYNTHESIS OF 3,3-DISUBSTITUTED 3-SILAGLUTARATES

Abstract Although polyhydrosilanes themselves react in the presence of rhodium(II) acetate dimer hydrate, it is possible to synthesize 3-silaglutarates by addition at 20°C of ethyl diazoacetate to a mixture of this catalyst and a dihydrosilane in methylene chloride. The yields of the silaglutarates are addition time dependent with an optimum value. This type of insertion of a carbenoid into an SiH bond was also used to prepare a silatriester from a trihydrosilane.

Oxidative rearrangement of bicyclo[n.1.0]alkan-1-ols in the presence of oxygen

Abstract Peroxidated compounds were prepared by treatment of ether solutions of bicyclo[n.1.0]alkanols with oxygen in the presence of silica gel, ferric acetylacetonate and light.

Preparation of (R)-veratryl- and (R)-(3-methoxybenzyl)succinates

Abstract LP-catalyzed hydrolyses of 4-cyanomethyl 1-methyl veratryl- and (3-methoxy benzyl)succinates lead in high optical yield to the corresponding (R)-butanoic acids. HLE-catalyzed hydrolyses of various methyl and cyanomethyl veratrylsuccinates lead to mixtures of propanoic and butanoic acids with medium enantioselectivity.

PREPARATION OF 2,3-EPOXYCYCLOALKANONES FROM BICYCLO[n.1.0]ALKAN-1-OLS

Copper- or iron-catalyzed oxidative rearrangement of bicy- clo[n.1.0]alkan-1-ols yields 3-hydroperoxycycloalkanones and/or bicyclic peroxyhemiketals, which are transformed into 2,3-epoxy- cycloalkanones by treatment with a base.

Enzymatic resolution of 3-substituted-4-oxoesters.

Abstract The lipase catalyzed hydrolysis of cyanomethyl 3-substituted-4-oxoesters was studied. With 3-methyl substituted esters, PPL led to optically active compounds. When the 3-substituent was a larger group, more satisfactory results were obtained with PL, especially if the substituent attached to the ketone function is other from methyl.

Spirovetivanes from silylated 1-hydroxycyclopropanecarboxaldehyde.

Abstract The spiro[4.5]decan-2-one and a spirovetivane, key intermediates of the [4.5] spirobicyclic sesquiterpenes, have been prepared from silylated 1-vinylcyclopropanols. A selective desilylation of enol ethers is featured.

Influence of the stereochemistry on the 1,2-dialkenylcyclobutanols behaviour : oxy-cope versus retro-ene rearrangements

Abstract From cyclobutanones 5a–j ,ten 1,2-divinylcyclobutanols 1a–j were prepared. A stereochemical effect was clearly evidenced : while trans 1,2-divinylcyclobutanols underwent a retro-ene ring opening, the cis isomers underwent an oxy-Cope ring enlargement.

Chemo-enzymatic preparation of optically active endo-bicyclo[4.1.0]heptan-2-ols

Abstract Resolutions of endo -bicyclo[4.1.0]heptan-2-ols were achieved by acylation in the presence of lipase from Candida antarctica (Novozym ® ). The (1 S ,2 R ,6 R ) enantiomers reacted faster and the enantiomeric ratios were between 60 and 800 for the 6-substituted bicycloalkanols.

Enzymatic resolution of bicyclo[n.1.0]alkan-1-ols derivatives: Preparation of optically active α-substituted α-methylcycloalkanones

Abstract Optically active α-methyl α-substituted cycloalkanones are prepared by a chemoenzymatic sequence which involves a Lipozyme® -catalyzed transesterification of 1-(chloroacetoxy)bicyclo[n.1.0]alkanes and ring opening of these cyclopropanol derivatives.