Metathese d'acetates d'alcools ω-insatures : Synthese de pheromones d'insectes

Esters of alkenoic acids, including insect pheromones as examples, have been synthesized using alkene metathesis reactions.     

Hydroboration d'amines insaturees: III - Reactions anormales d'hydroboration-alkylation d'amines propargyliques bromees

By hydroboration-alkylation of brominated propargylamines, we obtain brominated ethylenic amines and not the expected ethylenic amines with thexylalkylboranes. The thexyl group shows, in all cases, an anomalous high migratory aptitude.     

Stereochimie d'halogenation d'enols en serie exocyclique du cyclohexane

The steric course of the halogenation of exocyclic cyclohexyl enols E is not affected by the nature of halogenating species, medium, or substituent. In every case, equal amounts of axial and equatorial attack are formed. The results may be interpreted by a cyclic halogenation mechanism.     

Photochimie d'azido-steroides

Photolysis of azido-steroids leads to alkyl migration and 1–2 hydrogen transfer products. Pyrrolidine formation through an intermediate nitrene occurred in the case of 6β azido 5α-pregnane. Different excited states of azide and nitrene are considered.     

Sels d'atdp—19: Cinetique de decomposition d'un chlorure d'atdp en chlorure d'alkyle et HMPT. Effet de solvant et effet de sel

The kinetics of decomposition of the 2-methyl-1-pentyloxy(trisdimethylamino)phosphonium chloride, was measured in several solvents. The experimental kinetic order towards the chloride anion was in the range from 2, in a dissociating solvent, to 1 in non dissociating solvents. Hence we afford experimental confirmation of an earlier prevision in the literature. A linear correlation of log k with the dielectric constants of the solvents was found in the case of the systems exhibiting first order kinetics, contrasting with the classical correlation in $\text{1}\text{?}$, generally observed for the reactions between ions of opposite charge. The salt effect has been measured and interpreted. It allows the performance of kinetic runs for non hindered, very labile ATDP salts, by their replacement by a mixture of an ATDP perchlorate and an aryloxyphosphonium chloride, both of which are stable.     

Etude des interferences spectrophotometriques par utilisation d'une matrice d'experiences factorielle

(Use of a factorial design to study interferences in spectrophotometry.) Ozonation of aqueous solutions leads to the formation of hydrogen peroxide and oxalic acid. Hydrogen peroxide is determined spectrophotometrically by the classical method in which TiO·H₂O₂²⁺ is formed, but oxalic acid interferes by forming a complex with titanium. The interference is studied by using a simple factorial design. The results, calculated by linear regression, show the existence of both translational and rotational effects on the absorbance signals.     

Stereochimie d'heterocycles du groupe IVB—I : Syntheses stereoselectives d'alcoxy-1 et d'amino-1 sila-1 cyclobutanes

Stereoselective synthéses (60 to 90%) of some silacyclobutanes were performed by alcoholysis or aminolysis of 2 (or 3)-methyl-1-chloro-1-silacyclobutanes. Relative configurations of 2 (or 3)- methyl-1-alkoxy (or 1-amino)-1-silacyclobutanes thus prepared have been assigned from their NMR spectra. The mechanism of these stereoselective reactions, based on the rapid stereomutation of 1-chloro-1-silacyclobutanes, is discussed.     

Stereochimie d'heterocycles du groupe IVB—II : Syntheses stereoselectives d'hydrogeno-1 et d'alkyl-1 sila-1 cyclobutanes

The reaction between n-butyllithium and 1,2 (or 1,3)-dimethyl-1-t-butoxy-1-silacyclobutanes proceeds with retention of configuration at silicon, and yields 10/90 (or 80/20) Z/E mixture of 1,2 (or 1,3)-dimethyl-1-n-butyl-1-silacyclobutanes. Methylation of 2 (or 3)-methyl-1-t-butoxy-1-silacyclobutanes (Z/E = 15/85 or 65/35) by methylmagnesium iodide gives 15/85 (or 65/35) Z/E mixture of 1,2 (or 1,3)-dimethyl-1-silacyclobutanes. The proposed configurations for substituted silacyclobutanes are supported by spectroscopic data (RMN) and chemical results (correlation of configuration and stereomutation of hydrogenosilacyclobutanes).     

Reactivite d'hydrocarbures methylenecyclo-hexaniques—I : Stereochimie de la reaction d'oxymercuration-demercuration

Methylenecyclohexanes, prepared in excellent yield by Corey and Chaykovsky then Cornforth reactions, give on oxymercuration followed by reductive demercuration tertiary alcohols resulting from axial attack by solvent. The attack takes place trans to the substiuent when the latter is at the 2 position. α-Hydroxy or methoxy compounds behave similarly to each other. For acetoxy compounds, the cis alcohols are obtained preferentially, by intramolecular attack of acetoxy group on the mercurinium ion intermediate. The results can be explained satisfactorily on the assumption that the factors inducing stereochemistry are short distance interactions.     

Hydroboration d'amines insaturees: V. Nouvelle voie d'access aux aminoalkylidenecycloalkanes

Hydroboration of various 1-bromopropargylamines by borinane and 3,6-dimethylborepane has led to α-bromovinylboranes. Treatment of these compounds with iodine in basic media, only gives aminoalkylidenecycloalkanes with excellent yields.     

Reactions d'insertion d'aldehydes dans la liaison germaniumphosphore de germaphospholannes

The 1,2-addition reactions of aldehydes with the germaniumphosphorus bond of germaphospholanes lead to diastereoisomeric germoxyphosphepanes. An asymmetric induction of the chiral phosphorus atom is observed with preferential formation of sterically favoured diastereoisomers. This stereochemistry seems to derive from the four centered insertion concerted mechanism.     

Alcaloides steroidiques—CLXIV : Isomerisation en presence d'une base ou d'un acide d'oxazirannes steroidiques derives de la conanine

Isomerisation into an imino-carbinol or a nitrone is the first step in the hydrolysis of an oxazirane. This isomerisation, studied on three steroidal compounds lead to the following results: compound 6, bearing cis-oriented 18H and oxazirane ring, gives rise only to the nitrone 13. Compound 1 which bears trans 18H may isomerise either into the imino-carbinol 5 or into the nitrone 11 (11 is quantitatively obtained in acidic conditions with minimum basic catalysis). The case of compound 7 which isomerises whatever the conditions into the α hydroxylated imino-ether 8 shows the influence of structural factors which enhance the mobility of the 18H.     

Preparation d'acides β-amino-ethyl-phosphoniques

We describe a new, practical, synthesis of β-amino ethyl phosphonic acids. Organolithium reagents generated from nitriles are condensed with bis(dimethyl amino) chlorophosphates, followed by alkylation using phase transfer catalysis, reduction of nitrile group, and acid hydrolysis.     

Synthese d'azides tertiaires—V: Formation d'azido- et d'amino-8α et 8β dans la serie du labdan

HN₃/BF₃-Et₂O was used in the synthesis of tertiary azides from sclareol and dihydrosclareol. An ion-pair mechanism was observed. Under appropriate conditions, stereoselective introduction an azido-group at C-8 was observed. Manoyl-oxide and 13-epimanoyl oxide provided azido-ketones by CC vinylic fragmentation with loss of C₁₄ and C₁₅.     

Voie d'acces aux benzylidene-1 cyclohexadiene-2,4 fer tri-carbonyle et autres composes apparentes. Stabilisation singuliere d'une forme tautomere d'un aromatique

2,4-Cyclohexadien-1-yldimethylphenylphosphonium tetrafluoroborate obtained from the reaction of 2,4-cyclohexadien-1-yltricarbonyliron with PMe₂Ph in 96% yield, reacts readily with benzaldehyde in the presence of base to give 1-benzylidiene-2,4-cyclohexadienetricarbonyliron in 90% yield; this and other related reactions provide the first examples of the Wittig reaction adjacent to a tricarbonyl moiety.     

Phénylation d'alcools allyliques acycliques : II. Regioselectivite du transfert d'hydrogene

PdCl₂, HNaCO₃-catalysed phenylation of deuterium-labelled allylic butenols, a Heck type reaction, proceeds by a highly regioselective 1,2-hydrogen shift $\text{via}$ a Wacker type intermediate. No decomplexed enol was formed during this reaction.