Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 1ère communication. Nouvelle méthode de synthèse de β-hydroxyesters

A new synthesis of β-hydroxyesters involving a reaction between a carbonyl compound, ketene and an alkyl-orthotitanate is described. The following carbonyl compounds have been studied: aldehydes, ketones, α-diketones, α- or γ-ketoesters. A reaction mechanism is proposed.     

Reactivité de composés carbonylés avec des cétènes en présence d'alkoxydes de titane ou de zirconium. 3e communication

Reactivity of Carbonyl Compounds with Ketenes in the Presence of Titanium or Zirconium Alkoxides The reaction of ketene or dimethylketene with aldehydes or ketones in the presence of titanium or zirconium alkoxides gives essentially β-hydroxyesters. By polyinsertion of ketene and aldehydes in the Ti? O bond, di- tri- and tetraesters are formed. An excess of ketene produces acetyl derivatives of esters and 6-alkyl-3,4,5,6-tetrahydro-2,4-pyrandiones.     

Induction asymetrique—III: Stereochimie de l'addition du reactif de reformatsky issu de l'α-bromopropionate de methyle a diverses phenylalkylcetones. Determination des configurations relatives des β-hydroxyesters obtenus

A study of the reactivity of four aromatic ketones (C₆H₅-CO-R) with the Reformatsky reagent from methyl α-bromopropionate shows thatthe ratios of resulting diastereomeric β-hydroxyesters are unchanged, whether or not the chain R is lengthened or ramified. The relative configurations of those diastereomeric compounds are assigned by chemical correlation.     

Synthèse de nouvelles amidines bicycliques . Dérivés de la pyrimidine,de la quinazoline et de la diazépine-1,3

The synthesis of pyrrolo[1,2-α] pyrimidines is described. Several homologous compounds contain pyridine or azepine instead of pyrrole ring. They are obtained by cyclization of iminolactams with β-ketoesters, αβ-unsaturated esters, aldehydes or ketones, or diketene. The possibility of obtaining isomers is discussed.     

Dérivés de l'imidazo[2,1–b] thiazole. IV. Réarrangements au cours de la condensation de β-dicétones α-bromées avec l'amino-2 thiazole et la mercapto-2 imidazoline

Formation of 2-acetyl- (ro benzoyl-) imino-3-acetonyl- (or phenacyl-)-thiazolines and l-acetyl- (or benzoyl-)-2-acetonyl- (or phenacy l)-thioimidazolines by the action of α-halogenated β-di-ketones on 2-aminothiazole and 2-mercaptoimidazoline has been observed. These compounds resulted by nucleophilic attack followed by rearrangement and then cleavage of the intermediate carbinolamine. A dissymmetrical βdiketone rearranged unequivocally.     

Sur une méthode générale de synthèse des pyridones-2 condensées

Condensed 2-pyridones have been prepared by thermal cyclization of vinyl isocyanates substituted in β-position with aromatic heterocyclic radicals.     

Monofluoration quantitative par le phenyltetrafluorophosphorane influence de la température

The monofluorination by substitution of the hydroxyl group of the β-hydroxyesters of (o, m, p) Z - C₆H₄ - C(OH)R - CH R′ - COOR″ structure (where Z = halogen, methyl, methoxy, nitro and H) of 2,2,2 trichloroarylcarbinols by the phenyl tetrafluorophosphorane is described. The temperature at which the alkoxytrifluorophosphorane is decomposed, determines the nature (alkene alkoxytrifluorophosphorane, monofluorinated compounds) of the products and their yield. Knowledge of this temperature for erythro and threo isomers permits the selective fluorination of one them in a mixture.     

Sur la composition de l'arôme de thé

A gas-chromatographic investigation of black tea aroma has revealed, besides 19 known components, the presence of 4 new substances: 1-penten-3-ol, trans-2-hexen-1-ol, α-terpineol and β-ionone. The fragmentation pattern of 1-penten-3-ol has been determined by means of high resolution mass spectrography.     

Etude de la fragmentation par impact électronique de dérivés du benzothiazole

Study of Electron-Impact Fragmentation of Benzothiazole Derivatives The mass spectra of eighteen substituted benzothiazoles are reported and discussed. All these compounds are thermodynamically stable and give an intense molecular ion, which undergoes different types of fragmentation depending on the nature of the substituent which is rarely eliminated directly. β-Cleavage with respect to the heterocyclic double bond is often observed. Specific ²H-, ¹³C-, ¹⁵N- and ³⁴S-labelling have been used in order to confirm the fragmentation patterns.     

Migration du groupe éthoxycarbonyle dans la transposition de Wagner-Meerwein

Ethoxycarbonyl group migration in the Wagner-Meerwein rearrangement . 13 β-Hydroxy-esters have been treated with P₂O₅ in benzene at 80°. Olefin-forming dehydration, when possible, was found to be the main reaction. When this is excluded, tertiary or benzylic hydroxy-esters react in a manner most easily explained by migration of the COOEt group, thus avoiding the formation of α-carbonyl-carbenium ions. On the other hand, in primary hydroxy-esters (incapable of direct olefin formation), phenyl and methyl groups migrate in preference to COOEt, indicating in this case a concerted reaction.     

Sur la composition de l'arôme de Thé noir IV

17 substances were shown to be present in the aroma of black tea. This brings the total number of substances now identified to 187. Many of these new aromatic constituents are present only in traces. Nevertheless they possess an appreciable olfactive intensity whose flowery and/or fruity characteristics are found in many perfumed black teas such as: Kenya, Darjeeling, Ceylan, China and Oolong. The components were identified by GC/MS. and their presence in the aroma verified by GC.     

Etudes configurationnelles et conformationnelles de quelques chlorures de désoxy-6 β-L-héxopyrannosyle chlorosulfonyles et de leurs glycosides de méthyle

A total analysis of the NMR spectra of 6-deoxy-L -hexopyranoses in the α-configuration and of the corresponding β-anomers was carried out. The parameters obtained are characteristic of a 1C (L ) chair conformation, having the anomeric substituent in an axial orientation for the methyl α-fuco-, α-rhamno- and α-chinovopyranosides and for the α-fuco- and α-rhamnopyranosyl chlorides. The structure is also of a 1C (L ) chair type for the methyl β-fuco- and β-chinovopyranosides; the geometry is the same for the β-fuco- and β-rhamnopyranosyl chlorides despite the anomeric effect of a chlorine atom. However, the NMR parameters of the β-chinovopyranosyl chloride are not explicable on the basis of a chair conformation with an equatorial chlorine or a boat structure.     

Identification de la damascénone et de la β-damascone dans le tabac Burley

The successful identification of damascenone (I)

1 DORICENONE (trade mark of Firmenich & Cie, Geneva).

and β-damascone (III)

2 DORINONE (trade mark of Firmenich & Cia, Geneva)

in Burley tobacco oil was achieved through the use of an efficient vapour phase chromatography/mass spectrometry combination. Thus, the occurrence of β-damascone in nature and the presence of damascenone in an essential oil not related to rose oil were demonstrated.     

Catalyseurs Ziegler-Natta supportés sur MgCl2 pour la polymérisation stéréorégulée du propène. III. Systèmes catalytiques à hautes performances comprenant un solide ternaire: MgCl2, ester aromatique,TiCl4

An examination of the precatalyst which contains three compounds (MgCl₂–TiCl₄-aromatic ester) uncovered numberous properties that apparently are common to all precatalysts and have already been observed in the simpler systems: a continous decrease in the polymerization rate during polymerization, characterized by a deactivation index that does not depend on the precatalyst but only on the cocatalyst; isotacTiClty control by the [AI]/[aromatic ester] ratio in the cocatalytic solution; and fast and reversible control of kinetics and tacTiClty by the same ratio. The precatalyst prepared by impregnation of the aromatic ester in MgCl₂ or MgCl₂–TiCl₄ presents moderate or no improvement when compared with the simpler MgCl₂–TiCl₄ catalysts. The yellow precatalyst prepared by milling MgCl₂ with the aromatic ester and impregnating with TiCl₄ are the only products that provide high activity and isotactic index above 95% simultaneously, as revealed by the patent literature. Interpretation of the role played by the electron donor, based on infrared studies, are proposed: in the precatalyst it controls fixation of TiCl₄ on MgCl₂; in the cocatalytic solution it regulates the isospecificity of the active site by contact with the alkylaluminium-aromatic ester complex and slows polymerization. Free electron donor gradually poisons the active centers.     

Réactivité des esters de la carboxyméthylène-1 hydroxy-4 méthyl-6 pyridone-2 vis-à-vis des aldéhydes aromatiques

A Novel condansation of aromatic aldehyde with 2-pyrodone: 4-hydroxy-6-methyl-2-pyridone-1-acetate 1 and its 2 and 3 has been explored. It leads to the formation of arylmethenes 7 or 8 obtained by the reaction of one molecule of aldehyde with two molecules of 2-pyridone-2. The structure of all compounds was determined by pmr, cmr, mass spectra and ir. A reaction mechanism is proposed.     

Friedel-Crafts reactions catalyzed by samarium diiodide

Samarium diiodide is an efficient precatalyst for the Friedel-Crafts reaction involving various aromatic substrates and chelating electrophiles. Alkyl 3,3,3-trifluoropyruvates are transformed into α-hydroxyesters in good yields with total regioselectivity. In reactions involving an ethyl glyoxylate or a glyoxylic imine, α-hydroxyesters or α-aminoesters are obtained with variable amounts of products resulting from a double Friedel-Crafts reaction.     

Réactions de Friedel et Crafts de dérivés aromatiques sur les composés dioxo-1,4,2,3-non saturés. IV. Réactions des hydroxy-5-ouchloro-5-diméthyl-3,5- ou diméthyl-4,5-dihydro-2,5-furannones-2

Friedel-Crafts reactions of aromatic derivatives with 1,4-dicarbonyls 2,3-éthylenic compounds. Part IV. Reactions of 5-hydroxy or 5-chloro 3,5-dimethyl or 4,5-dimethyl 2 (5 H) furanones We studied the Friedel-Crafts reactions of 2-(5H)-furanones. In the presence of sulfuric acid and of an aromatic derivative, 5-hydroxy- or 5-chloro-5-methyl-2-(5H)-furanones with one methyl group either in the 3 position, or in the 4 position generally give the corresponding 5-aryl-2-(5H)-furanones, while with aluminium chloride, it is possible to obtain, when a reaction takes place, isomeric 1H-indenecarboxylic acids. However, in a particular case, an addition to the substrate's double bond is observed. The 3-aryl-5-hydroxy-tetrahydrofuran-2-one obtained is methylated in two ways and gives either a cyclic product, or a linear one. In two cases tautomerism between 1H-1-indenecarboxylic acid and 1H-3-indenecarboxylic has been shown by ¹H-NMR.     

Addition de dérivés maloniques sur des β-énaminones cycliques

The addition of activated acctonitriles 6 on cyclic and benzylic β-enaminoketones 5 under basic conditions (sodium ethoxide or trition B) have been investigated. This reaction leads exclusively to the formation of α-pyrones 8 and never to the pyridine ring. The strucutre of the newly synthesized α-pyrone derivatives 8 are supported by nmr and ir spectral data.     

Action d'organolithiens sur la méthyl-2 quinoxaline. Etude de la réactivité des adduits

The action of organolithium reagents such as phenyllithium or n-bulyllithium on 2-methylquinoxaline gave lithiation of the methyl group which upon reaction with electtropholesphiles produce side chain alkenyl derivatives. On the other hand organolithium reagents react with the quinoxaline azomethine bond to give I-lithio-2-alkyl)or ary-1)-3 methylquinoxalines which can be further loithiated on the methyl group to give 2-alkyl(or aryl)-3-alkenylquinoxaline derivatives. The adducts can be condensed with clectrophiles such as benzonitrile or methlyl benzoate but only methyl benzoate leads to N condensed derivatives. Furthermore substituted 1,2,3,4-terahydroqinoxalines are available via the above lithio intermediates.     

Synthetic transformations of higher terpenoids: XXII. Reactions of lambertianic acid derivatives with organozinc reagents obtained from ethyl bromoalkanoates

Reactions of 16-cyanomethyllambertianate with organozinc reagents obtained from ethyl esters of α-bromoacetic, α-bromopropionic, and α-bromobutyric acids gave the corresponding enaminoesters, β-ketoesters, and β-hydroxyesters of labdanoids whose yield depended on the reaction conditions and the structure of the α-bromoester. By Reformatsky reaction of 16-formylmethyllambertianate with α-bromoesters of carboxylic acids stereoisomeric β-hydroxyesters of labdanoids were synthesized.