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.     

RMN 13C d'α alcoxy-indenes et d'α alcoxy-styrenes : Topologie electronique du systeme Π et une reflexion sur la relation entre deplacement chimique et reactivite dans les ethers d'enol

¹³C NMR chemical shifts of ethylenic carbon atom C_β of α alkoxy-indenes and α-alkoxy-styrenes are affected by the conformation of the OR group with respect to the double bond and hence the efficiency of p- Π conjugation but, contrary to previous results, δC_α is not affected. The phenyl group exerts a diamagnetic Π- effect on C_α and C_β which is a function of its dihedral angle with the double bond. Although δC_β is especially sensitive to the Π-electron density, the chemical shifts of the ethylenic carbons are best understood by considering the total charge density. The σ and Π contributions to the total charge density are discussed using the preferred conformation of the molecules. This approach strongly suggests that the correlation between the gradual shift of δC_α to low frequency and the gradual shift of δC_β to high frequency (relative to TMS) as R changes from RCH₃ to RtC₄H₉ in certain series of enol-ethers is not due to pΠ conjugation variations. This method of interpreting ¹³C NMR shifts, as opposed to previous methods, is compatible with explanations of other physico-chemical properties of alkyl vinyl ethers. Although it is sometimes possible to correlate the gradual shifts of δC_β with (σ + Π) electron density variations in a homogeneous series, it seems impossible to predict the relation. In all cases, there is no evident correlation between gradual shifts of δC_β(orδC_α) and the reactivity of enol ethers because one cannot consider the role of the out-of-plane conformation of the alkoxy group (which increases from RCH₃ to RtC₄H₉); however, the out of plane conformation does not have an identical effect on δC_β and the reactivity.     

Comparaison entre la protolyse du diméthylcadmium et celle d'un alcoolate mixte. Étude des équilibres et des réactions d'échange.

PMR studies show that CH₃CdOC(CH₃)₃ is formed more rapidly than symmetrical alkoxide from (CH₃)₂Cd and (CH₃)₃COH. Spectra of CH₃CdOC(CH₃)₃ in different solvents show that this product is less solvated that (CH₃)₂Cd. An interpretation based on exchange of methyl groups in various cases is proposed.     

Reactions de dechlorhydratation d'organochlorohydrogermanes et -polygermanes

1,8-Diazabicyclo[5.4.0]undec-7-ene appears to be an efficient dehydrochlorination agent for the organochlorohydrogermanes PhCl₂GeH, R₂ClGeH (R = Et, Ph). In diluted solutions the intramolecular α-elimination process leads to germylene through germanate

formation while in concentrated solutions intermolecular reactions are predominant and give organochlorohydropolygermanes in good yields. The latter reaction is an interesting and selective way to obtain digermanes with bulky substituents (R = mesityl).Both intra- and inter-molecular dehydrochlorination mechanisms are discussed.     

Synthese et structure d'amino-4 aza-2 dienes-1,3

The action of enamines on tosylated isonitrosomalonic derivatives leads through substitution of the tosyloxy group to substituted 4-amino-2-aza-1,3-dienes. The structure and the configurational (respectively conformational) stability of the 4-amino-2-aza-1,3-dienes suggest a restricted rotation about the C₄N bond, a fast rotation about the C₃C₄ bond and the configurational stability of the azomethinic bond.     

L'extraction des lanthanides et des actinides par les oxydes d'alkylphosphine : L'extraction del'acide nitrique par quelques dioxydes de diphosphine

The distribution of nitric acid between an aqueous phase of constant or variable ionic strength and a benzene solution of diphosphine dioxide can be explained by the following reactions H⁺_a+ NO_3^-a+ DiPO₀ ? D1PO·HNO₃₀ H⁺_a+ NO_3^-a+ DiPO·HNO₃₀ ? DiPO·2 HNO₃₀ At constant ionic strength, the stability constants K₁″ were determined for the complexes 1,1-DiPO·HNO₃ (98 ± 01 (M)^-1), 1,4-DiPO·HNO₃(44±3 (M)_-1) and 1,5-DiPO·HNO₃ (51 ± 1 (M)^-1). The constants K₁₁″ for the complexes 1,1-DiPO·2 HNO₃ and 1,5-DiPO.2 HNO₃ are respectively 035±001 (M)^-1 and 62 ±0.05 (M)^-1 at 25°. With an aqueous phase of variable ionic strength, values of K₁'=54±7 (M)^-2 for 1,5-D1PO.HNO₃ and K_II'=65 ± 04 (M)^-2 for 1,5-DiPO·2 HN0₃ were obtained     

Etude des petits cycles—XXXVI. Photo-oxygenation d'alkylidenecyclopropanes. Syntheses specifiques d'alkenylcyclopropanols,de β′-hydroxy α-enones et d'α,α′-dienones

The dye-sensitized photo-oxygenation of alkylidenecyclopropanes 1a–4a at –50°C gives the hydroperoxydes 1b–4b, which were reduced in situ by PPh₃ into 1-alkenylcyclopropanols 1c–4c in high yield. At higher temperatures, 1b–4b rearranged exclusively into β′-hydroxy α-enones 1d–4d if pyridine was added (α,α′-dienones 1e–4e are also formed competitively in absence of pyridine). At 3°C the photosensitised oxygenation of alkylidenecyclopropanes 1a–4a gives ketones 1k–4k, cyclobutanones 1i–4i and β′-hydroxy α-enones 1d–4d. The origin of products is discussed.     

Photoreduction d'arylcetones par les amides et les lactames: applications synthetiques

Benzophenone is photoreduced by lactams and amides. In this reaction the hydrogen atom α to the lactam nitrogen is abstracted regioselectively, and radical coupling leads to adducts. The reaction is general and comparable to an hydroxyalkylation α to the nitrogen atom. Its quantum yield is 0.13 in the case of N-methyl 2-pyrrolidone in CH₃CN or in C₆H₆. Adducts obtained with acetophenone and p,p'-dimethoxy benzophenone are described. The reduction of adduct 12yields the diphenylethanolamine 22 and 12 is dehydrated to give the enamide 21.     

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.     

L'extraction des lanthanides et des actinides par les oxydes d'alkylphosphine : L'extraction de L'acide nitrique par les oxydes de tri-n-hexylphosphine,de tri-cyclohexylphosphine et de tri-n-octylphosphine

The distribution of nitric acid between an aqueous phase and a solution of THPO, TcHPO and TOPO in benzene was measured at 25°. The apparent stability constants K₁' were found to be 17.2±1.0 (M)^-2 for THPO.HNO₃, 7.0±0.8 (M)^-2 for TcHPO.HNO₃ and 15.2 ± I.I (M)^-2 for TOPO.HNO3. The stoichionetry of the last complex was confirmed in n-octane solution at constant ionic strength in the aqueous phase.     

L'extraction des lanthanides et des actinides par les oxydes d'alkylphosphine: Tome 1. l'extraction de l'acide nitrique par l'oxyde de tri-n-butylphosphine

The distribution of TBPO, water and nitric acid has been measured between an aqueous phase and various inert diluents at 25°. This study allowed the determination of the apparent stability constants for two molecular complexes, TBPO . HNO₃ (K₁=17.5±1.3 (M/l)^-2 (benzene); 20.1±0.8 (M/l)^-2 (toluene); II±2(M/l)^-2 (n-hexane) and TBPO . 2HNO₃.H₂O (K₂=(2.9±0.3) 10^-3(M/l)^-2 (benzene)).     

Complexes dinucleaires pontes des metaux d8: VII. Reactions d'addition oxydante d'halogenures d'alkyle et d'acycle aux complexes μ-halogenes du rhodium(i) [RhX(CO)(PR3)]2. Structure cristalline de [RhCl(CO)(PMe2Ph)(Me)(Br)]2

The halogen bridged binuclear complexes of rhodium(I) [RhCl(CO)(PR₃)]₂ undergo oxidative addition with methyl halides to yield the complexes [RhCl(CO)(PR₃)(Me)(X)]₂ (X = Cl, Br). The crystal and molecular structures of [RhCl(CO)(PMe₂Ph)(Me)(Br)]₂ have been determined from a single crystal by use of X-ray crystallographic methods. The space group is Pca2₁ or Pacm with a 19.501(5), b 10.381(4), c 13.641(5) e? Z = 4. Parameters of 30 nonhydrogen atoms in the space group Pca2₁ were refined by the full-matrix least squares technique to a conventional R factor of 0.073. In a binuclear unit, each rhodium atom is in an octahedral environment being bonded to a carbonyl group, a methyl group and a tertiary phosphine ligand and three halogen atoms for which, due to a disorder phenomenon, the diffusion factors have been determined as the average between those of chlorine and bromine atoms. In solution the cis-migration of the methyl groups occurs, leading to the acetyl complexes. In the case of CH₃I, it is shown that an equilibrium is present in solution: [RhCl(CO)(PR₃(Me)(I)]₂ ? [RhCl(COMe)(PR₃)(I)(solvant)]₂] Carbonylation reactions shift this equilibrium to give the complexes [RhCl(CO)(COMe)(PR₃(I)]₂. Such complexes are readily prepared by direct oxidative addition of acyl halides to the compounds [RhCl(CO)(PR₃)]₂.     

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.     

Synthese univoque d'amines tertiaires insaturees par voie organometallique a partir de sels d'immonium : II. Synthese d'amines β- et α-ethyleniques

In this work, the best method to prepare unequivocally and in good yields β-and α-ethylenic tertiary amines: RR′CHNR″₂ (R unsaturated group, R′, R″ alkyl groups), from immonium salts, has been evaluated.     

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.     

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'organometalliques vis a vis des enynes conjugues α, α'-bifonctionnels: III. Enynes a groupement alcool en α de la triple liaison: Synthese d'allenes et de dienes mono- ou bifonctionnels

Organolithium, organomagnesium and organozinc compounds react with α,α'-difunctional enynes: HOCH₂CCCHCHCH₂Y (Y  OH, OCH₃, N(CH₃)₂). This reaction produces one or two derivatives, according to the nature of the metallic group: mono- or di-functional allenes, mono- or di-functional dienes.     

Systemes de strecker et apparentes—II : Mécanisme de formation en solution aqueuse des α-alcoylaminoisobutyronitrile à partir d'acétone,d'acide cyanhydrique et d'ammoniaque,methyl ou diméthylamine

The formation of N-substituted tertiary α-aminosobutyronitriles from acetone, alkali, cyanide amine, has been studied in aqueous solutions of pH 8–12. Competition between the cyanide and amine for acetone first favours cyanohydrin formation. The α-aminonitrile is then slowly formed. The kinetic study of the reaction, as a function of cyanide concentration, shows two successive slow steps. In the presence of excess cyanide, the first step, limiting the reaction rate, is formation of intermediate imine. This is catalysed neither by OH^? or H₃O⁺ and depends only on the concentration of amine in basic form. The mechanism of the second step, the imine forming the α-aminonitrile, is discussed in terms of acid catalysed addition of the cyanide ion to the imine.     

Hydroboration d'amines insaturees—II: Régio et stéréosélectivité de l'hydroboration-alkylation d'amines acétyléniques

The hydroboration reaction of acetylenic amines R¹R²NCH(R³)CCR⁴ was studied. We report the first results of a study of the reactivity of dialkylborane R₂BH towards these amines which allow us to propose a new method for the synthesis of differently substituted β-ethylenic amines. The regioselectivity and the stereoselectivity of this reaction are examined and allow us to set out the possibility of a trans hydroboration.     

Synthese et reactivite d'oxycyclopropanes electrophiles

“Electrophilic oxycyclopropanes” 4 to 6 have been prepared starting from olefins 7. Ring opening of these cyclopropanes occurs under very smooth conditions (DMSO, room temperature). A push-pull type system is then also a powerful driving force with regard to the C-C bond cleavage in cyclopropanes.