A. Gaudemer

Insertions photochimique et spontanée d'oxygène dans les liaisons cobaltcarbone des alcoylcobaloximes

Abstract Some alkyl(pyridinato)cobaloximes irradiated with visible light insert molecular oxygen into the cobaltcarbon bond to give stable peroxidic compounds; the alkyldioxycobaloximes. This insertion reaction also occurs without light with alkylcobaloximes having a cobaltcarbon bond in a benzylic position.

Mise en évidence de l'hydrure des cobaloximes(I)

Abstract (α-Styryl)pyridinecobaloxime, obtained by reacting pyridinecobaloxime(I) with phenylacetylene under neutral conditions, results from the cis addition of the hydride form of cobaloxime(I) to the triple bond of phenylacetylene. Formation of this hydride is observed during the thermolysis of (2-hydroxy-1-phenylethyl)pyridinecobaloxime. Cis -addition of the hydride to a triple bond has been observed only in the case of phenylacetylene.

Étude des mécanismes de rupture de la liaison cobalt3-carbone des alcoylcobaloximes: Thermolyse et photolyse en l'absence d'oxygéne

Abstract Thermolysis and photolysis of alkylcobaloximes RCH(R′)CH(R″)Co(DMG) 2 Py in the absence of oxygen are shown to proceed via the same β-elimination reaction: reaction products are in both cases the ethylene derivative RR′CR″H and the cobaloxime(I) hydride HCo(DMG) 2 Py which is characterised by its reaction with phenylacetylene.

Constituants amers deBrucea amarissima structures des brucéines A, B et C

Evidence is presented for the structures (II a), (II b) and (II c) for the bruceines A, B and C, the bitter principles isolated from the seeds ofBrucea amarissima.

Structure de la glaucarubinone nouveau principe amer isole de Simaruba glauca

Resume Un nouveau principe amer, la Glaucarubinone, a ete isole des graines de Simaruba glauca. Il est montre que cette substance a la formule (IIa).

Etude du mecanisme de l'hydrogenation des esters insatures catalysee par la vitamine B12 ou les cobaloximes

Abstract (Pyridinato)cobaloxime(II), chloro(pyridinato)cobaloxime(III) and vitamin B 12 catalyse the hydrogenation of α,β-unsaturated esters by H 2 or NaBH 4 . A study of the mechanism of this reduction has shown that: ( a ) one of the hydrogen atoms added is from the solvent, the other from the reducing agent, ( b ) hydrogenation is not stereospecific, ( c ) a σ alkylcobalt complex is an intermediate.

Réactions d'insertion d'oxygène moléculaire dans les liaisons cobalt-carbone d'allyl-, d'allényl, et de propargyl-cobaloximes☆

Abstract The reaction of molecular oxygen with alkylcobaloximes R-Co)dmg) 2 Py (R = allyl, allenyl-, propargyl- or alkenyl-) leads to the corresponding peroxo derivatives, ROOCo(dmg) 2 Py. In the case of allylcobaloximes partial or total isomerisation of the allyl radical occurs during the insertion. Allenyl- and propargyl-cobaloximes give, in each case, the corresponding propargyl dioxycobaloximes.

E´tude de la nucle´ophilie de la pyridinatocobaloxime(I): Ste´re´ochimie de la re´action avec les haloge´nures vinyliques

Abstract The reactions between cobaloximes(l) and vinyl halides yield alkenylcobaloximes in which the double bond has retained its configuration. The formation of acetylenic intermediates during these reactions is ruled out. This suggests that the nucleophilic substitution of halogen by cobalt(I) occurs by an addition-elimination mechanism.

Etude par rmn de la conformation des (1-indanyl)cobaloximes et des (1-indanyl)dioxycobaloximes

Abstract Pyridinecobaloxime(I)reacts with indene and indene oxide to give (1-indanyl)pyridinecobaloxime (I) and (2-hydroxy-1-indanyl)pyridinecobaloxime (II) respectively. Oxygen insertion into the cobalt-carbon bond of these compounds yields the corresponding peroxo derivatives. Probable stereochemistry for these compounds is deduced from their NMR data.

Structure du vernolide, nouvel ester sesquiterpeniqueisolé de vernonia colorata

Raoul Toubiana et Alain Gaudemer Institut de Chimie des Substances Naturelles, 91-Gif -sur-Yvette, France. (Received 24 January 1967) Vernonia colorata est une composee d’bfrique noire (region d’Adiopodoum8). A partir d’un extrait chloroformique des graines, nous avons pu isoler une substance cristallisle F: 180-183” (avec decomposition), [a] D = +230” (CHCl ) 3’ C H 0” que nous avons 19 22 7 appelee vernolide et pour laquelle nous proposons les formules l