Solvolyses de derives de spiro[2.3]hexyle-4

Solvolysis and acid catalysed isomerisation of spiro[2.3]hexyl derivatives are versatile synthetic routes to 2-(Δ¹-cyclobutenyl)ethyl alcohols and methylenecyclopentanols. The course of the reactions is discussed.     

Sur la composition de l'arôme de cacao

A gas-chromatographic separation of cocoa aroma, followed by infra-red and mass-spectrometric identification, has yielded, besides 22 of the 91 previously described constituents, 35 new substances (8 aliphatic, 1 alicyclic, 7 aromatic, 9 o-heterocyclic, 4 pyrrolic, and 6 pyrazinic).     

Sur la composition de l'arôme de tomate

A gas-chromatographic investigation of tomato aroma has revealed 46 components of which 32 are new. The isolation and identification of 2-isobutyl-thiazole, substance for the first time found in a natural aroma, are given in detail.     

Rearrangement photochimique de 4h-pyrannes et de dienones en 2h-pyrannes

The photoreactivity of the 4H-pyrans 1 was studied in detail by fluorescence and phosphorescence, by deactivation measurements for the singlet state and by the determination of the accessible quantum yields and rate constants. The photochemical isomerisation of the 4H-pyrans 1 into 2H-pyrans 2 occurs with concerted migration of the benzyl group, in a singlet state as a sigmatropic 1, 3-transposition. The 2H-pyrans 2 are also obtained by irradiation of the nonconjugated dienone isomers 3 of the 2H-pyrans 2.     

Réactions de cyclisation de pentynyl-2 pyrimidones-4

Acetylenic amindines HC≈?C·(CH₂)_n·C(?NH)NH₂ give, by condensation with β-ketoesters, pyrimidones substituted on carbon 2 by an acetylenic chain. Two types of evolution are observed when compounds are heated without any catalyst. The minor route is a cyclization by attack on a triple bond by the amidic nitrogen atom. The main reaction is a cycloaddition involving the non activated triple bond and an azadienic system, leading to non isolated tricyclic intermediates which retrocyclize to stable bicyclic compounds.     

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.     

Calcul de l'equilibre conformationnel de la fluoro-4 cyclohexanone

The equilibrium constant of 4-fluoro cyclohexanone has been determined by means of the knowledge of the electronic structures of the axial and equatorial isomers and the calculation of the solute—solvent dipolar and quadrupolar interactions made with field reaction theory. The axial isomer is largely predominent.     

Selectivite de la reduction de cyclohexen-2 ones par NBu4BH4 dans divers solvants et par NaBH4 dans des conditions de transfert de phase

The 2-cyclohexenone 1 and isophorone 2 reductions with NBu₄BH₄ in aprotic solvents lead to a highly preferential 1–4 attack; i.e. 85% with 1 and 96% with 2 in THF. These regioselectivities are nearly the same as those observed with LiBH₄ in the presence of[2.1.1) cryptand confirming thus the cation influence. This method which is inexpensive and easy to work up, seems to constitute a general way to reduction of α-enones to saturate alcohols while other reagents such as K(sec Bu)₃BH are not able to reduce the carbon-carbon double bond of isophoron.Phase transfer catalysis conditions are not useful for selective reduction: large amounts of allylic alcohols are formed in liquid-liquid phase transfer conditions (60% in toluene-water); a good regioselectivity is only obtained when a cryptand is used as a transfer agent in solid-liquid conditions.     

Deplacements homolytiques intramoleculaires-I : Etude de la decomposition du perpentene-4 oate de t-butyle dans les cyclanes. synthese de cycloalkyl-5 pentanolides-4

The thermolysis of t-butyl-4-peroxypentenoate 1, in cyclohexane led to several compounds; the main product was 5-cyclohexyl-4-pentanolide (yield 35%). Hypotheses are proposed to explain their formation. The lactone could be obtained by two different mechanisms: a concerted one and a two-step one (cyclohexyl radical addition to the double bond of the perester leading to a discrete radical followed by an intramolecular displacement of a t-butoxyl radical). The thermolysis of 1 has synthetic interest: several original 5-cycloalkyl-4-pentanolides have been obtained by this way.     

Synthese de F-alkyl-2 hydroxy-4 quinoleines

F-alkynes and F-alkynyl esters are versatile intermediates for the synthesis of F-alkyl substituted heterocyclic compounds.Condensation of these compounds with aniline and its derivatives, followed by cyclisation of intermediates obtained (enamines and imines), is in fact the only way of synthesis of hydroxy-4 quinolines substituted in position 2 by a F-alkyl chain other than CF₃.     

Structure Cristalline de l'Arseniate Double de Potassium et de Zirconium: KZr2(AsO4)3

Crystal Structure of KZr₂(AsO₄)₃ KZr₂(AsO₄)₃ crystals have been prepared by the flux method. The compound crystallizes in the rhombohedral system with the parameters: a = 9.028(1), c = 24.399(3) Å. The density is d = 3.694 g/cm³ and Z = 6. The space group is R3 c. The structure has been solved by isotypism with that of NaZr₂(PO₄)₃ to R = 0.041, for 353 independent reflections. It consists in 3-dimensional chains of AsO₄ tetrahedra and ZrO₆ octahedra. K⁺ ions are the center of the antiprism with K—O distances equal to 2.813 Å. The Zr–O and As–O distances have the same values of those usually observed (Zr–O = 2,05 Å and As–O = 1.66 Å).     

Sur la composition de l'arôme de thé noir II

Trans-2-penten-1-ol, 1-ethyl-2-formyl-pyrrole, 2-trans, 4-cis-heptadienal, phenyl-acetonitrile, methyl benzoate, 2-phenyl-but-2-enal and the lactone of 2,6,6-trimethyl-2-hydroxy-cyclohexylidene acetic acid have been separated from black tea aroma by gas-liquid chromatography, and identified by infra-red and mass spectrometry.