Monoacetamidation de quelques hydrocarbures polycycliques par voie electrochimique

Anodic oxidation in acetonitrile of five polycyclic hydrocarbons gives products in ratios related to the relative stabilities of intermediate carbocations. If “non-classical” ions form they arise apparently from “classical” transition states.     

Comparaison des transformations polyreactionnelles induites par les chlorure et bromure de pyridinium : Cas de l'hexanediol-1,6

Pyridinium chloride and bromide react with 1,6-hexanediol through a complex multireactional chain process mostly furnishing unsaturated hydrocarbons, cyclic ethers, unsaturated halides and unsaturated alcohols. The similar transformations undergone by 5-hexene-1-ol and 1-hexanol under the same conditions suggest several hypotheses about the mechanism. Several original assignments from ¹³C NMR data were involved in determining the structures of the products.     

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.     

Action de l'anhydride acétique sur les (aziridinyl-1)-2 tétra-hydropyrannes et sur les dialkylamino-2 tétrahydropyrannes: Influence des substituants de l'azote sur l'orientation de la réaction

The 2-(1-aziridinyl)tetrahydropyrans cannot be obtained by aminolysis of the 2-dialkylaminotetrahydropyrans. These compounds are synthesized by the Hofmann reaction between 2-chlorotetrahydropyrans and ethylenimine. The effect of acetic anhydride on the 2-(1-aziridinyl) and 2-dialkylaminotetrahydropyrans was studied. The 2-dimethylaminotetrahydropyrans were converted into 2-acetoxytetrahydropyrans and dimethylacetamide by cleavage of the carbon-nitrogen bond. Ring opening of the oxygen heterocycle gives the corresponding dialkylacetamides and polymerised products. The 2-(1-aziridinyl)tetrahydropyrans allow the synthesis of the N-(2-tetrahydropyrannyl)-N-(2-acetoxy-ethyl)acetamides. Acetic anhydride ring opens the nitrogen heterocycle.     

The unusual reaction of 2-isocyanatophenyl acetate with amines and water

The reaction of 2-isocyanatophenyl acetate with adamantyl and phenyl-containing amines gave the corresponding acetamides. Intermediate 2-isocyanatophenol formed in the course of the reaction undergoes intramolecular cyclization to 2-benzoxazolinone. These reactions proceed only with amines possessing basicity (pK_b > 3.80).     

Systemes de strecker et apparentes—XI : Formation et stabilité de l'α-carboxyaminonitrile.Intermédiaire essentiel dans la synthèse des hydantoïnes selon bucherer-bergs

The determination of the structure of the intermediate in the Bucherer-Bergs reaction (the transformation in aqueous solution of an aldehyde into the corresponding amino-acid via the hydantoin) showed that this reaction involved the formation of α-aminonitrile carbamate. The slow formation of the carbonic anhydride from the carbonate buffer limited the formation of that main intermediate which was in equilibrium with the α-aminonitrile. The variation of the stability of the carbamate vs pH is mainly determined by the concentration of CO₂ dissolved in the mixture, but also by the equilibrated formation of products formed by the degradation of α-aminonitrile, i.e. the aminodinitrile and the cyanohydrin.     

The use of Cr (CO)6 as an alternative CO source in Pd‐catalyzed C‐N bond formation: Synthesis of benzamides

An efficient strategy for the synthesis of benzamides from acetamides and aryl iodides using 1 mol% Pd (OAc)₂ as catalyst and Cr (CO)₆ as CO‐precursor is described. This new synthetic methodology displays high functional group tolerance on both substrates and avoids the need for ligands, reducing agents, or other additives. The corresponding products were obtained in good to excellent yields at atmospheric pressure under mild reaction conditions.     

Solvolysis-decomposition of 2-adamantyl chloroformate: evidence for two reaction pathways

Reaction of 2-adamantyl chloroformate under a variety of solvolytic conditions leads to 2-adamantyl chloride accompanied by solvolysis products, some with and some without retention of the CO(2) unit. For example, in 100% ethanol, only 4.8% 2-adamantyl chloride is formed with the mixed carbonate (88%) being the dominant product, and in 100% 2,2,2-trifluoroethanol, the products are both formed with loss of CO(2), 59% of the chloride and 41% of the ether. With exclusion of the specific rates in 100% and 90% ethanol and methanol, a good Grunwald-Winstein plot against Y(Cl) values (solvent ionizing power) is obtained, with a slope of 0.47 +/- 0.03. The results are compared with those reported earlier for 1-adamantyl chloroformate and isopropyl chloroformate and mechanistic conclusions are drawn.     

New rearrangement in the adamantylation reaction of 4-iodophenol and 4-iodoanisole

A reaction of 2-iodophenol and 2-iodoanisole with 1-adamantanol in trifluoroacetic acid gives the corresponding 4-(1-adamantyl) derivatives. Similar adamantylation of 4-iodophenol and 4-iodoanisole is accompanied by migration of the iodine atom from para- to ortho-position, giving 4,6-di(1-adamantyl)-2-iodophenol and 4-(1-adamantyl)-2-iodoanisole, respectively, as the reaction products.     

Cinetique complexe de l'halogenation de cetones en milieu acide—II : Controle par la diffusion des vitesses d'halogenation des enols-consequences

The kinetics of the bromination and chlorination of acetone, diethylketone and di-isopropylketone (bromination only) have been studied at [X₂]_a^o ≈ 10^?7 to 10^?5 M; the apparent rate constants k_II^X₂ = K_Ek₂^X₂ (where K_E is the keto-enol equilibrium constant) for iodination, bromination and chlorination are approximately equal. This result is attributed to diffusion-controlled kinetics. The order of magnitude of such a limiting rate constant, 10⁹ M^?1s^?1 calculated from Smoluchowski's equation, leads to new values for K_E in solution (1·5 x 10^?8 for acetone) much smaller than those in the literature. The rate constants derived for enol ketonisation are then in good agreement with those from proton addition to the corresponding enol ethers.     

Photoréactivité de dérivés de l'acide carbonique en milieu réducteur

Photoreduction of carbamates, thiocarbamates and carbonate occurs in a mixture of HMPTH₂O. A better yield of alkane is observed for thiocarbamates. Formates and photoFries products are also isolated from the reaction mixture. Radical intermediates can be trapped by cyclohexene even in HMPA.     

Chimie organométallique: IV. Réversibilité de l'amination des complexes diènes-palladium (II)

An elimination reaction takes place with palladium compounds arising from the reaction of benzylamine with 1,5-cyclooctadiene—PdCl₂ (IV) and 1,5-hexadiene—PdCl₂ (VI) complexes. Evidence for this retroamination reaction is given by the reaction of hydrogen chloride on the cyclooctadiene derivative (V) and by a study of the products resulting from the amination of the hexadiene complex (VI) under various conditions.     

Telomeres photoreticulables—1. Synthese de telomeres photoreticulables a partir du cinnamate et de l'acetate de vinyle

Photocrosslinkable telomers containing cinnamoyl groups can be prepared by two methods, viz, (i) direct telomerisation of vinyl cinnamate using either redox initiation (FeCl₃ benzoin-CuCl₂) or conventional radical initiation (benzoyl peroxide), and (ii) esterification of polyvinylalcohol telomers with cinnamoyl chloride. The former method gives products which are extensively cyclised, as indicated by i.r. and NMR spectra, whereas the latter method gives materials in which all the cinnamoyl groups are available for crosslinking.     

Synthesis of substituted anilides of the alkaloid cytisine and molecular structure of <Emphasis Type="Italic">N</Emphasis>-(2′,6′-dichloro-4′-nitrophenyl)-2-<Emphasis Type="Italic">N</Emphasis>-cytisinoacetamide

Anilides of cytisinylacetic acid were synthesized by reaction of the alkaloid cytisine with 2-bromo-N-(2,6-dihalo-4-nitrophenyl)acetamides. The compositions and structures of the products were confirmed by IR and PMR spectroscopy, mass spectrometry, and x-ray structure analysis.     

Synthèse de pyrimidines et purines adamantylées par alkylation régiosélective directe,en catalyse par transfert de phase

The use of 1-adamantyl bromomethyl ketone, under phase transfer catalysis conditions permits the regioselective N₁ alkylation of uracil and thymine,the N₁,N₃ dialkyl derivatives. The observed selectivity is discussed in relaxation with the structure of the alkylating agent.     

Action des halogenures d'alkylmagnesium sur les pyrones-2—VI : Etude de la regioselectivite de l'ion enolate intermediaire de la reaction

Grignard reagents normally react with 2H-pyrones to yield unsaturated ketols, dihydropyranols, dienones and 2H-pyrans. In some cases, products are obtained by attack on the most sterically crowded position of the enolate ion. Since steric hindrance is an unsatisfactory basis for predicting the reactivity, we have applied a theoretical study to this problem. The model used is based on an enlarged electronic delocalization in the transition state, and allows the interpretation of the regioselectivity of the reaction.     

Cinetique complexe de l'halogenation de cetones en milieu acide—I : Iodation des enols

The kinetics of the iodination of acetone, diethylketone and di-isopropylketone in aqueous media ([H₂SO₄] = 0·1 to 1·0 N; [I₂]_a^o = 10^?7 to 10^?5M) have been studied by couloamperometry under irreversible conditions. At these concentrations the rates of formation of the enol and of its iodination are similar. The general equation, which assumes the steady state approximation for the enol, is applicable, and is used to separate the rate constants of enolisation (k₁) and the apparent enol iodination rate constant (k_II^I₂ = K_Ek₂^I₂). For acetone, the value given by Schwarzenbach for the enol equilibrium constant (K_E = 2·5 x 10^?6) leads to an elementary rate constant for the addition of iodine to the enol (k₂^I₂ = 6·5 x 10⁶ M^?1s^?1). This value is not, however, consistent with k_I2 = 1·5 x 10⁸ M^?1s^?1, the rate constant for the iodination of the corresponding ether 2-ethoxypropene.     

Adamantylazoles: XII. Alkylation of 1-R-tetrazole-5-thiones and 1-R-tetrazol-5-ones with tertiary alcohols in sulfuric acid

In the reaction of 1-(1-adamantyl)-4,5-dihydro-1H-tetrazole-5-thione with 1-adamantyl in sulfuric acid 2-(1-adamantyl)-5-(1-adamantylsulfanyl)-2H-tetrazole and 1,3-bis(1-adamantyl)-5-(1-adamantylsulfanyl)-1H-tetrazolium salt are formed. Methylation of 1-(1-adamantyl)-4,5-dihydro-1H-tetrazole-5-thione in alkaline medium affords 1-(1-adamantyl)-5-methylsulfanyl-1H-tetrazole while its interaction with formaldehyde affoeds 1-(1-adamanttl)-4-(hydroxymethyl)-4,5-dihydro-1H-tetrazole-5-thione.     

Analyse conformationnelle a l'aide de la notation des angles de torsion—III: Controle conformationnel de certaines reactions de type sn2' ou sni' de derives cyclohexeniques faisant intervenir un deplacement allylique de l'olefine

To take place stereoselectively S_N2' reactions of cyclohexene derivatives require an axial leaving group either on a half-chair (suprafacial reaction) or on a 1,3-diplanar form or a boat (antarafacial reaction). These conclusions appear generally relevant to concerted reactions of cyclohexenic derivatives involving an allylic migration of the olefinic bond.     

Neutron diffraction evidence for anion sublattice disordering in alkali earth fluorides at high temperatures

High temperature powder neutron diffraction studies of calcium, strontium and barium fluorides indicate that there are large thermal motions associated with the anions. This suggests that the anion sublattice in these compounds with the fluoride structure may disorder at temperatures below the melting points. In S:F₂ this disordering appears at about 1370 K and for BaF₂ at about 1300 K. This is in good agreement with transitions of 1440 K and 1240 K, predicted from thermodynamic data.