René Couffignal

Sur la reaction de reformatsky : II. Preparation et reactivite des organozinciques issus des γ-bromosenecioates d'ethyle et d'isopropyle

Abstract The one-step condensation of a carbonyl compound with alkyl γ-bromo-β-methylcrotonate (alkyl γ-bromosenecioate) and zinc, is carried out in methylal at 0°C. The reaction can give three products after hydrolysis: one transposed hydroxyester (allylic transposition as regard to the original bromoester), two untransposed ( E ) and ( Z )-hydroxyesters and one lactone, derived from the in situ cyclisation of the previous ( Z )-hydroxyester. At the alcoholate step, the reaction is an equilibrium. In favorable cases, it is possible to obtain the lactone exclusively. On the other hand, organozinc compounds derived from alkyl γ-bromosenecioate yield, after hydrolysis, a conjugated ester (alkyl senecioate) and a non-conjugated isomeric ester. The two-steps condensation of a carbonyl compound with these organometallics gives, after hydrolysis, the same results as the one-step condensation.

Acylation des enolates lithiens d'esters ou de cetones au moyen d'anhydrides mixtes carboxyliques et carboniques: preparation de β-cetoesters et de β-dicetones

Abstract Lithium esters and ketoenolyllithium compounds react with mixed carboxylic and carbonic acid anhydrides to give, respectively, β-ketoesters and β-diketones in satisfactory yields.

Preparation et reactivite du derive lithie issu du dioxolanne du -ceto pentanoate de trimethylsilyle.

Resume The organolithium reagent 4 issued from trimethylsilyl 4,4-ethylendioxypentanoate 3 reacts with ketones; it affords β-hydroxy-acids 7 and β-ethylenic ketones 8 . This reaction is an efficient route for carbonyl olefination. 4 also acts towards mixed carboxylic and carbonic anhydrides as a homoenolate equivalent.

Preparation de β-cetonitriles via l'acylation du cyanacetate de trimethylsilyle par les anhydrides mixtes.

Abstract β-ketonitriles R1COCH2CN and R1COCH(R2)CN are respectively prepared from (CH3)3SiOCOCHLiCN or R2CHLiCN by acylation reaction with mixed anhydrides RCOOCO2Et.

Changes in fatty acid and lipid composition of wheat when treated with a chemical hybridizing agent

Abstract The effects of the chemical hybridizing agent RH0007 (CHA or gametocide) on the fatty acid composition of mature seeds, anthers and leaves of Triticum aestivum were investigated. The fatty acid composition of seeds of treated plants showed small but significant variations compared with control material. Total lipid content of treated seeds decreased markedly with gametocide treatment. Fatty acid composition and repartition of polar lipids of anthers were not drastically altered by the treatment. In anthers of treated plants, linoleic acid content rose as oleic and linolenic acid percentages fell. Foliar sprays of CHA induced drastic decreases in chlorophyll and carotenoid contents of treated leaves. Changes in fatty acid composition were not so marked as for pigment levels. Changes observed for anthers and leaves could be correlated with a secondary herbicide effect of the gametocide but not with a primary action.

Synthese de β-ethoxycarbonyl λ-lactones

Abstract β-ethoxycarbonyl β, λ-insaturated λ-lactones 2 are easily prepared by dehydration of β-acyl β-ethoxycarbonyl α-alkyl propionic acids. Otherwise the condensation of these acids with allylzinc reagents produces β-ethoxycarbonyl λ-lactones 3 with a β-ethylenic carbon chain branched on the λ-carbon of the lactone.

Magnetic non-equivalence in nuclear resonance. Part V. Geminal allenic protons

Magnetic non-equivalence in the chemical-shift sense of geminal allenic nuclei, is introduced into allenic bromo-ketones by an asymmetric carbon atom in the δ position with respect to the terminal methylene.The magnitude of the chemical-shift difference between anisochronous protons depends on the nature and concentration of the solvent. This behaviour allows the direct determination of the geminal coupling constant.