C. Agami

Stéréochimie-l. contrôle orbitalaire de la stéréochimie des réactions—I : Méthylation comparée d'anions énolates et diénolates

Resume Alkylation by methyl iodide of enolates of decalone and octalone involves different stereoselectivity when an olefinic double bond is present. Examination of secondary orbital interactions between frontier orbitals explains why the electrophilic reagent (LUMO) approach takes place in different spatial areas depending whether it concerns an enolate or a dienolate anion (HOMO).Resume Alkylation by methyl iodide of enolates of decalone and octalone involves different stereoselectivity when an olefinic double bond is present. Examination of secondary orbital interactions between frontier orbitals explains why the electrophilic reagent (LUMO) approach takes place in different spatial areas depending whether it concerns an enolate or a dienolate anion (HOMO).

Chimie organométallique: IV. Réversibilité de l'amination des complexes diènes-palladium (II)☆

Abstract An elimination reaction takes place with palladium compounds arising from the reaction of benzylamine with 1,5-cyclooctadiene—PdCl2 (IV) and 1,5-hexadiene—PdCl2 (VI) complexes. Evidence for this retroamination reaction is given by the reaction of hydrogen chloride on the cyclooctadiene derivative (V) and by a study of the products resulting from the amination of the hexadiene complex (VI) under various conditions.

Stéréochimie—LIV : Influence du degre de substitution de la double liaison éthylénique sur la stéréochimie de l'hydrocyanation 1,4 de cétones conjuguées

Abstract The topological isomerism between octalinones in which the enone group has two distinct locations does not lead to any difference on the stereochemistry of the hydrocyanation of these substrates; the cyano group is axial in the kinetically controlled products. On the contrary, the stereoselectivity is strikingly reversed when the enone group is substituted by a methyl β to the carbonyl, leading to the introduction of the cyano group in an equatorial configuration in the kinetically controlled products.

Stereochimie—LII. Controle orbitalaire de la stereochimie des reactions—III: Effets des groupes β-fluoro et β-cyano sur la stereochimie et la cinetique de la reduction de cyclohexanones par le tritertiobutoxyaluminohydrure d

Abstract The respective influences of β-fluoro and β-cyano groups on the reduction of ketones by Li(t-BuO)3AlH on the stereoselectivities of the reduction with and without added cryptands, and with and without added alkye fluoride and nitrile, were compared with ab initio calculations using the frontier orbitals of analogous carbonyl compounds to give energy values.

Chimie organome´tallique: III. Me´canisme de la formation du de´rive´π-allylique du cyclooctadie`ne-1,3 complexe´par le chlorure de palladium

Abstract The complex 1,3-cyclooctadiene—PdCl 2 is shown to be an intermediate lin the synthesis of the π-allylic derivative of 1,3-cycloctadiene. The complex undergoes nucleophilic substitution with methanol followed by acid catalyzed elimination of methanol. Utilization of 1-methyl01,3-cyclooctadiene as a ligand shows that the substitution reaction of the solvent takes place by an S N 2′ process.

Stéréochimie—LIII. controle orbitalaire de la stéréochimie des réactions— IV : Hydrocyanation 1,4 de céto-3 Δd1-steroïdes et d'octalones apparentées

Abstract Hydrocyanation at sites other than ring junctions does not exhibit the same stereoselectivity in the keto-3Δ1-steroid series as in analogous bicyclic compounds. Irrespective of the presence or the absence of an angular methyl group, the kinetic product has always an axial cyano group; however a stereoelectronic control of the reverse reaction explains why under thermodynamic conditions, only enones of the decalin series give both axial and equatorial epimers. A conformational analysis based on the conservation of the torsion angle and the maximum overlap of orbitals accounts for these facts.

Stereochimie—li controle orbitalaire de la stereochimie des reactions—ii : Reductions par le tritertiobutoxyaluminohydrure de lithium de cyclohexanones substituees en β par des groupes nitriles et methyles en position ax

Abstract LiAlH(O-tBu)3 reduction of 2-decalones and 5α-cholestane-3-ones, unsubstituted or β-substituted by axial or equatorial CN or CH3 groups show relative rates of attack on both sides of cyanodecalones and decalone which can be interpreted in terms of orbital control by axial C-H bonds α and α to the carbonyl group. With axial methyl groups, the stereoselectivity depends on unequal 1,3 diaxial interactions which induce ring flattening favouring this orbital control.

Effet conformationnel dans l'alkylation de dienolates cycliques

Abstract Stereoselectivities of enolate and dienolate methylations in the decalin series are compared : with dienolates, conformational effects account for the observed differences when the additional double bond is located at the ring junction.

A stable σ-allyl organopalladium compound. X-Ray structure of the dimeric complex(C8H11PdCl)2

The allyl palladium complex obtained from cyclo-octa-1,5-diene is shown to be a σ-allyl complex.

Controle stereoelectronique de la retrohydrocyanation des cetones conjuguees

Abstract Analogous β-cyanoketones in bicyclic and steroid series exhibit different behaviours towards retrohydrocyanation; stereoelectronic effects can be invoked to explain this dissimilarity.