Cyanures d'acyle ethyleniques V : Addition conjuguee des ethers d'enols trimethylsilyles.

Conjugate addition of silyl enol ethers to ethylenic acyl cyanides leads to δ-keto-acids or methyl esthers after hydrolysis or methanolis of reaction products.     

Epoxydation d'aldehydes et de cetones par un procede de transfert solide-liquide

The condensation reaction of trimethylsulfonium iodide with variously functionalized aldehydes and ketones in the presence of solid potassium hydroxide in acetonitrile leads to the selective formation of the corresponding epoxides in high yields. The method used calls upon a solid-liquid transfer process.     

Stereochimie comparative de bromation,dans l'ether,d'enolates lithique et potassique,d'ethers d'enol methyliques et d'enols en serie 4-t.butyl 1-benzoyl cyclohexane et en serie β-phenyl butyrophenone

The steric course of bromination of cyclic and acyclic metal enolates in ether, independent of the nature of the metal (lithium or potassium), is identical to that of enols but very different from that of methyl enol ethers. The stereochemical results are compatible with the previously postulated six-centre cyclic halogenation mechanisms of enols     

Sur une cause d'erreur dans le dosage par voie humide de l'azote dans les aciers speciaux

The estimation of nitrogen in normal or special steels by the Kjeldahl method can give results that are too high if the acid used to dissolve the steel (even “pro analysi” acid) contains impurities such as nitrates, and if the metal itself contains even negligible amounts of molybdenum (e g a few ten-thousandths). In this case the blank test can nevertheless give a very weak or negative result.In order to ascertain from this point of view the quality of the acid used, it is necessary to compare the nitrogen contents obtained on a sample with a very low nitrogen content, e g electrolytic iron, in the absence or in the presence, respectively, of a minute addition (about 0.1%) of molybdenum. The difference between these determinations should be negligible. If it is not, then the acid tested should be rejected, or distilled before use.     

Etude de la solvolyse des tosylates d'aryl-2 propyle dans le dimethylformamide

Aryl-2 propyltosylate solvolysis occurs in DMF as in a protic medium, via two competing mechanisms: solvent nucleophilic substitution (rate constant k_s) unimolecular solvolysis with aryl participation (k_Δ). Nucleophilic solvent participation is more important in DMF than in a protic solvent; this is due to the lack of electrophilic assistance of DMF compared to a hydroalcoholic solvent (k_Δ^DMF < k_Δ^{EtOH aq.}), DMF and aqueous carbon nucleophilicities being nearly the same (k_s^DMF ? k_s^{EtOH aq.}). Charge distribution in transition states are of the same type in both solvents.     

Effets polaires dans les reactions de transfert homolytique intramoleculaire d'hydrogene

In this paper we analyse the influence of a phenyl substituent on the relative rates of the 1–5 and 1–6 intramolecular hydrogen transfers. Compared to the abstraction of an aliphatic H atom, the activation energy for the abstraction of a benzylic H atom is smaller. The effect is nevertheless more important with a primary alkyl radical (1,3 kcal/mole) than with an alkoxy radical (0,9 kcal/mole. This can be analysed in terms of a polar effect. In addition, the size of the effect is too small to make a short distance transfer of a H-atom feasible; this is in keeping with the statement that H atom migration requires a linear transition state.     

Sur la non-equivalence des liaisons CH du groupement methyle dans les complexes cristallises de trans-bromotetracarbonyle methyle carbyne de chrome

The syntheses, ³¹P{¹H} NMR spectra, and a structure of “mixed” 1,5-cyclo-octadienebis(tertiary phosphine)dirhodium complexes possess a rhodiumrhodium bond, briding diphenylphosphido and two different stereochemistries around the rhodium atoms. One rhodium is tetrahedral and surrounded by four phosphorus atoms and the other rhodium (bonded to COD) is nearly planar.