Etude theorique (cndo/s) des etats excites et des transitions electroniques de 2h-chromenes representant la partie responsable de l'ouverture photochimique de spiropyrannes

The excited states and electronic transitions of some 2H-chromenes (considered responsible for photochemical opening of photochromic spiropyrans) have been studied. The relative positions of nπ^* and ππ^* singlet and triplet energy levels of these compounds allow a satisfactory interpretation of their optical properties. Also highly localized electronic charge transfers are demonstrated in the case of 2H-chromenes substituted by a nitro group.     

Synthese des substances de groupe sanguin—IV : Synthese du 2-acetamido-2-desoxy-4-O-[2-O-(α-l-fucopyranosyl)-β-d-galactopyranosyl]-d-glucopyranose,porteur de la specificite H

The synthesis of a H blood group specific trisaccharide was performed by using benzyl ethers as temporary blocking groups for hydroxylic functions. Benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-d- glucopyranoside was glycosylated by 3,4,6-tri-O-benzyl-1,2-O-benzyl-1,2-O-(tert-butoxyethylidene)-α-d-galactopyranose; after O-deacetylation, glycosylation by 2,3,4-tri-O-benzyl-α-l-fucopyranosyl bromide, and hydrogenolysis, 2-acetamido-2-deoxy-4-O-[2-O-(α-l-fucopyranosyl)-β-d-galactopyranosyl]-d-glucopyranose is obtained.     

Synthese des substances de groupe sanguin—IX: Une synthese du 2-o-(α-l-fucopyranosyl)-3-o-(α-d-galactopyranosyl)-d-galactose,le determinant antigenique du groupe sanguin b

The trisaccharide 2-O-(α-L-fucopyranosyl)-3-O-(α-D-galactopyranosyl)-D-galactose has been synthesised stereospecifically using the imidate procedure. Allyl 3-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside was first α-L-fucosylated by 1-O-(N-methyl)-acetimidyl-2,3,4-tri-O-benzyl-β-L-fucopyranose then, after O-debenzoylation, α-D-galactosylated by 1-O-(N-methyl)-acetimidyl 2,3,4,6-tetra-O-benzyl-β-D-galactopyranose. The resulting tri-saccharide has also been obtained from allyl 2-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside after α-D-galactosylation, O-debenzoylation and α-L-fucosylation. The glycosylations were performed at room temperature in nitromethane in the presence of p-toluenesulfonic acid. Deallylation followed by catalytic hydrogenolysis gave the B blood-group antigenic determinant. The allyl group was also selectively transformed into hydroxyethyl group.     

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie I. Etude du pentafluorotellurate IV de lithium LiTeF5

Lithium pentafluorotellurate (IV) LiTeF₅ has been prepared by different methods:

• •slow evaporation of a 1/1 mixture of lithium fluoride and tellurium dioxide or tellurium tetrachloride in anhydrous hydrogen fluoride,
• •heating a 1/1 mixture of lithium fluoride and tellurium tetrafluoride. LiTeF₅ is orthorhombic

(a = 9,52 Å b = 9,12 Å c = 11, 60 Å)     

Synthese de la trifluoromethyl-vinyl-cetone

The synthesis of trifluoromethylvinylketone $\text{6}$ is described. The metal hydride reduction of ethyl trifluoroacetoacetate $\text{1}$ gives the glycol $\text{2}$. Selective tosylation of $\text{2}$ occurs on the primary hydroxyl group and leads to $\text{3}$. Tosyl-chloride exchange produces the chlorohydrin $\text{4}$ which is oxydized to the β chloroketone $\text{5}$. The dehydrohalogenation of $\text{5}$ leads to the fluorinated ethylenic ketone $\text{6}$.     

Synthese et cyclisation electrophile de la bromhydrine de l'acide homogeranique

A new synthesis of 5-bromohexahydro-4,4,7a-trimethyl-2($\text{3H}$)-Benzofuranone (3aα,5β,7aβ)($\text{1}$) was achieved by electrophilic cyclization of the bromohydrin issued from pure homogeranic acid.     

Vinylallenes—VI : Synthese de cetones de la serie de la jasmone

Dehydrojasmone 1a and nor-methyl dehydrojasmone 1b have been prepared by action of a peracid on appropriately substituted vinylallenes. Several pathways to these hydrocarbons are described.     

Synthese et reactivite de nitrones portant en α un groupe butadiene-fer tricarbonyle

Nitrones bearing a butadieneiron tricarbonyl moiety in the α position are easily prepared. These stable compounds show good reactivity in 1,3-dipolar cycloaddition reactions.     

Synthese de chlorofluorovinylsilanes et de quelques derives

Several chlorofluoroolefins were prepared from 1,1-dichloro-2,2-difluoroethylene via chlorofluorovinylsilanes.     

Nitroxydes-LXVIII : Synthese et etude cinetique de la decomposition du t-butyl isopropyl nitroxyde. Effet isotopique

Decomposition of t-butyl isopropyl nitroxide and its β²H-labelled homologue has been examined by UV and EPR. The bimolecular reaction does not show reversible formation of a dimer, but exhibits an isotope effect (k_H/k_d)_30°C?9 which shows that the rupture of the CH bond is involved in the slow step of the decomposition. The β proton coupling constant, determined by NMR, is +1.84 G.     

Recherches sur la synthese totale des alcaloides appartenant a la serie de la carpaine et de la cassine—V : Synthese totale de l'acide (±) carpamique

The total synthesis is described of (±) 6-(7-carboxy hept-1-yl) 3-hydroxy 2-methyl piperidine [(±) carpamic acid] in five steps from 1-ethoxycarbonyl 6-methyl hept-5-en-2-one.     

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie II: Etude des fluorotellurates d'ammonium NH4TeF5 et (NH4)2TeF6

New methods of synthesis:

• •reaction of aqueous or anhydrous HF with TeO₂ and NH₄F or NH₄HF₂, with (NH₄)₂TeCl₆
• •reaction of TeF₄ with NH₄F or NH₄HF₂
• •reaction of NH₄HF₂ with TeO₂

have been investigated for NH₄TeF₅ and a new compound (NH₄)₂TeF₆. The resulting compounds have been analysed and characterized.