Couplage selectif d'azaallyllithium et d'arylallenes : synthese generale d'arylmethylenepyrrolidines

1–3 Cycloaddition of 1,3-diphenyl-2-azallyllithium with arylallenes affords a general synthetic method for arylmethylenepyrrolidines, a new class of five-membered-heterocycles.     

Method d'estimation des limites d'inflammabilite

We have employed the criteria defined by the CHETAH (ASTM) program to predict the lower and the upper flammability limits of various organic compounds. The results obtained for molecules containing carbon, hydrogen, oxygen and nitrogen are, in most cases, in good agreement with experimental values. The difficulties encountered when the molecule contains a heteroatom can be overcome by knowledge of the stoichiometric conditions of the combustion reactions.     

Determination de la constante d'acidite intrinseque d'un echangeur d'ions carboxylique

To obtain the intrinsic acidity constant of a carboxylic ion-exchanger, we propose a method of graphical double extrapolation. The results for an ion-exchanger made of polyvinyl alcohol grafted with acrylic acid are close to those published for the corresponding linear polyacid.     

Coupures alcalines d'ethers bi-tertiaires et d'alcools

Heating αα′-tetrasubstituted ethers with sodium amide at 225–300° leads to smooth cleavage of one of the α-substituents, which is reduced in the process; the Intermediacy of an alkoxide ion is postulated, and a high yield cleavage of a tertiary alkoxide is indeed observed.     

Synthese ambidoselective d'enamines et d'imines siliciees

Trimethylchlorosilane reacts with organotin imines or enamines leading mainly (or only) to the corresponding silicon enamine. In contrast, the silylation of lithium or magnesium iminates gives only the isomeric imine when the nitrogen is hindered by bulky groups (i-Pr, t-Bu).The study of the NSi ? CSi equilibration shows clearly that in both cases the isomer obtained is the kinetic product of each reaction.These results show that a proper choice of both the metal associated with the iminate and of the iminate itself allows the formation of each isomer in a pure state.     

Mecanisme d'ignifugation d'elastomeres organosiliciques par le platine

The role of platinum and of some mineral oxides in improving the thermal stability of a silicone rubber has been studied by temperature-programmed thermogravimetric analysis and by isothermal pyrolysis. Platinum has no significant influence on the scission of side chains. It limits the rupture of the polymer backbone by preventing the formation of a transition complex involved in silicone degradation. Mineral oxides combine with certain products of the thermal decomposition of the polymer.     

Action d'organozinciques α-ethyleniques sur le chloroformiate d'ethyle: preparation d'esters β-ethyleniques

The reaction of organozinc compounds RCHCHCH₂ZnBr with ethyl chloroformate gives β-ethylenic esters CH₂CHCH(R)COOC₂H₅ in good yields; these esters are readily converted to the corresponding α-ethylenic esters on treatment with piperidine.     

Reactivite du tetraallyletain et d'allyltrialkyletains vis a vis d'aldehydes,de cetones et d'epoxydes

Tetraallytin reacts readily with non activated ketones and exothermically with aldehydes contrary to other allylic organotins such as allytributyltin. Homoallylic alcohols are obtained after acidolysis of the adducts. Upon extended heating, allylic organotins and epoxides form products which correspond to additon products of isomeric carbonyl compounds. However, starting from cis- and trans-1-phenyl-1,2-epoxypropanes, direct regiospecific but non-stereospecific ring opening is observed with poor yields.     

Existence d'isomeres e et z d'ylures de cycloimmonium

E and Z isomers of p-nitrobenzoyl, 4-p-tolyl[1-2-4]triazolum methylide 5b and p-nitrobenzoyl, 4-p-phenyl[1-2-4]triazolium methylide 5e, have been characterised.     

Alkylamidation d'organometalliques par les sels d'oxoimminium-1,3 cycliques

Dialkylcuprolithium reagents are efficiently condensed at low temperature onto N-Methyl 2-(2,4,6-trimethyl) cyclo 1,3-oxoimminium salts giving rise specifically to the corresponding alkylamides.     

Reactions photochimiques d'amines tertiaires et d'alcaloides—III

Photo-oxidation reactions, sensitized by methylene blue, of various tertiary amines and alkaloids have been studied. An immonium ion is postulated as an intermediate in the formation of secondary amines and of some cyclization and dimerization products.