Marcel Gaudemar

Action des organomagnesiens sur les ethers-oxydes propargyliques en presence de bromure cuivreux: synthese de carbures alleniques

Abstract Grignard reagents react, in ether and at room temperature, with propargylic ethers, to give allenic hydrocarbons with reasonable yields. The reactions requires catalytic amounts of copper(I) bromide.

Erythro or threo selective aldol-type reaction via (z)s-silyl ketene s,n acetals

Abstract N-dialkyl thioamides can be converted stereoselectively into (Z)N-dialkyl S-trimethylsilylketene S,N acetals 2 . Condensation of 2 with benzaldehyde in the presence of TBAF or Lewis acids catalysis affords erythro (R*R* or threo (R*S* β-hydroxythioamides selectively.

Regioselectivity of S-silylketene S,N acetals and titanium - (ate) - enethiolates addition to unsaturated ketones

Abstract (Z) S-Silylketene S,N acetals react with α-enones to afford exclusive 1-2 addition. Titanium enethiolates and titanium - ate - complexe enethiolates undergo 1-2, 1-4 addition.

Reactivite des propargyl- et allenyl-boronates de dibutyle vis-a-vis des derives carbonyles : I. Condensation d'aldehydes et de cetones peu encombres

Abstract Allenylboronates react with aldehydes and ketones to give unsymmetrical borates. Alcohols are obtained after hydrolysis in 50-80% yields. With sterically unhindered carbonyl compounds boronates react by the propargyl-allenyl rearrangement.

erythro- or threo-selective aldol-type reaction via (Z)-N,N-dimethyl-S-trimethylsilylketene S,N-acetals

Abstract N,N -Dimethylthioamides can be converted stereoselectively into ( Z )- N,N -dimethyl- S -trimethylsilylketene S,N -acetals, 2 . Condensa under the influence of a catalytic amount of tetrabutylammonium fluoride affords erythro -( R ★ , R ★ )-β-hydroxythioamides selectively in good yields. The aldol reaction is postulated to proceed via an acyclic transition state. Lewis acid-promoted condensation of 2 with benzaldehyde on the other hand affords mainly threo -( R ★ , S ★ )-β-hydroxythioamides when R 1 is not too bulky.

Sur les zinciques issus des α-bromonitriles : I. Préparation, structure et réactivité avec les aldéhydes, les cétones et les alcoylidènes malonates d'éthyle

Abstract Organozinc compounds derived from α-bromonitriles are readily prepared in solution in tetrahydrofuran (THF) and exist in the C metallated form. They condense normally with aldehydes and saturated ketones. A number of new β-hydroxy-nitriles are described. The addition of conjugated unsaturated ketones results in the formation of β-hydroxynitriles or ketonitriles, depending on the nature of the initial bromonitrile. The stereochemistry of the reaction of benzaldehyde with zinc-α-bromonitrile is not influenced by the nature of the solvent. Condensation with diethyl-malonate alkylidenes lead to the expected 1,4-addition products.

Reactivite des propargyl- et allenyl-boronates de dibutyle vis-a-vis des derives carbonyles : II. Generalisation et etude des divers facteurs reactionnels

Abstract Ketones react with dibutyl allenylboronate to give borates. Except acetone, acetophenone and cyclohexanone which give only acetylenic compounds, condensation of all ketones studied results in the formation of a mixture of acetylenic and allenic borates, the ratio of which depends on the bulkiness of the ketone, the proportions of reactants used and the temperature and solvent. These condensations are under kinetic control and the allenic product has an unrearranged structure.

Reactivite des propargyl- et allenyl-boronates de dibutyle vis-a-vis des derives carbonyles III. Stereochemie de la condensation sur les aldehydes

Abstract Condensations of aldehydes with allenyl boronates are stereoselective. The assignment of configuration is made on comparison of chromatographic, NMR and IR data.

S-silyketene s,n-acetals. cross-aldol type condensation reaction with schiff bases.

Abstract S-silylketene S,N-acetals react with Schiff bases to afford β-aminothioamide in good yields. The reactivity of the title acetals is compared to that of corresponding lithium-enethiolates.

Synthese directe de cetones par reaction de reformatsky

Abstract The Reformatsky reaction of nitriles, with α-bromo salts , gives, after neutral hydrolysis, ketones in good yield. Nitriles with particulary mobile α hydrogens, such as benzyl cyanide, react in the same way. The reaction mechanism has been studied.