- Amberlyst-15-catalyzed efficient cyclization of γ-and δ-unsaturated alcohols: Green synthesis of oxygen heterocycles
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Amberlyst-15 (H+) resin catalyzes efficient cationic endo-cyclization of-and-unsaturated alcohols to yield tetrahydro-(2H)-pyrans and oxepanes. The merits of the present protocol are good yield of the products under mild conditions, simple workup, and reusability of the resin.
- Singh, Soni A.,Kabiraj, Shilpi,Khandare, Reena P.,Nalawade, Shrikant P.,Upar, Kiran B.,Bhat, Sujata V.
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experimental part
p. 74 - 80
(2010/03/24)
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- Cerium(IV) ammonium nitrate (CAN): A very efficient reagent for the synthesis of tertiary ethers
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Treatment of tertiary 1,4- and 1,5-diols with cerium ammonium nitrate at room temperature led to the corresponding tetrahydrofuran and tetrahydropyran derivatives in high yield-and stereoselectivity. Utilizing this methodology, manoyl oxide (25a) and a variety of fragrant compounds, such as linalool oxide (8), caparrapi oxide (12), ambrox (14) and other related amber-gris-type odorants have been synthesized; 16 examples are described. Georg Thieme Verlag Stuttgart.
- Alvarez-Manzaneda,Chaboun,Alvarez,Cabrera,Alvarez-Manzaneda,Haidour,Ramos
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p. 1829 - 1834
(2008/02/08)
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- A PRACTICAL SYNTHESIS OF MYRCENOL BY PALLADIUM COMPLEX-CATALYZED ELIMINATION REACTION
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A Palladium complex-catalyzed elimination reaction of allyl amines was studied to establish a practical process for production of myrcenol.The catalytic elimination occurred smoothly with the cationic Pd(II) complexes.Among a variety phosphorous ligands, the tetramethylene and the pentamethylene diphosphine ligands proved to be the best ligand with respects to the catalytic activity and selectivity.
- Kumobayashi, Hidenori,Mitsuhashi, Shigeru,Akutagawa, Susumu,Ohtsuka, Sei
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p. 157 - 160
(2007/10/02)
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- Etude des phenomenes physico-chimiques intervenant lors du procede d'hydrodistillation
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During the steam distillation of aromatic plants, some terpenic compounds undergo various chemical reactions (hydrolysis, elimination, cyclisation rearrangement) which depend on the acidity of the water in which the plant is soaked.In order to study the physical and chemical phenomena involved in this process and in particular the formation of artefacts, we have performed steam distillation experiments on lavender flowers in a buffered aqueous medium.The essential oils collected are rich in linalol and linalyl acetate, two monoterpenic compounds known for their propensity to undergo heat induced transformations.At pH 4 or 7, the chromatograms of the essential oils are similar whereas in a more acidic medium (pH = 2), the degradation of linalyl acetate gives rise to a number of terpenic products (α and γ terpinenes; 2,6,6-trimethyl 2-vinyl tetrahydropyran; 1,4-cineol, cis and trans ocimenols, myrcenol, terpin 1-en 4-ol, etc.).A study of the reactions involved during the thermal degradation of linalyl acetate in a model experiment (heating to reflux) as well as the determination of the kinetic parameters, show that some terpenes, present in lavender oil originate in part from the transformations of linalyl acetate during steam distillation.Furthermore, the decomposition of this ester is directly and quantitatively related to the concentration of acid in the medium (pseudo first order rate constant is 0.008 min-1 at pH 7 and 0.0147 min-1 at pH 2).It is therefore necessary to control and maintain the pH of the water during steam distillation to avoid the alteration of the essential oils by formation of artefacts and preserve the integrity of the oil originally present in the plant.The study of the various steam distillation fractions gives informaiton on the kinetics of the steam distillation of the various components which apparently do not depend only on the boiling point but also on their polarity (hydrodiffusion phenomenon).
- Morin, Ph.,Gunther, C.,Peyron, L.,Richard, H.
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p. 921 - 930
(2007/10/02)
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- Cyclisation des alcools δ-alleniques par le nitrate d'argent ou les sels mercuriques. Synthese d'α-alcenyl-2 tetrahydropyrannes
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Eight diversely substituted δ-allenic alcohols have been synthesized by using three different methods for the formation of the allenic linkage.When treated with silver nitrate or mercuric salts, these alcohols are transformed in fairly good yields into α-alkenyl-2 tetrahydropyrans.In addition to its regioselectivity in the formation of the heterocycle this reaction shows in certain cases a high stereoselectivity.Alcohols monosubstituted on the thermal allenic carbon lead to more than 90percent of the E product whereas the 2,4 or 2,6 disubstituted tetrahydropyrans are obtained in predominantly the Z configuration.
- Audin, Patrick,Doutheau, Alain,Gore, Jacques
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p. 297 - 306
(2007/10/02)
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- Process for the catalytic synthesis of conjugated dienes from dialkylallylamines
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There is disclosed a novel process for converting allylic amines, having a hydrogen bonded to a carbon δ to the amino group, to a diene in the presence of a zero valent palladium phosphine complex and a weak acid. The process has been used to make novel compositions containing 7-methoxy-3,7-dimethyloctadienes which are useful as odorants and flavorants.
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- FACILE PREPARATION OF 2,6-DIMETHYL-2,6-TETRAHYDROPYRANCARBOLACTONE, A VERSATILE INTERMEDIATE FOR THE SYNTHESES OF (+/-)-FRONTALIN, (+/-)-CINENIC ACID, AND (+/-)-LINALOYL OXIDE
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2,6-Dimethylcyclohexanone has been converted via its 2,6-dihydroxy derivative by base-catalyzed oxygenation to 2,6-dimethyl-2,6-tetrahydropyrancarbolactone which can be used as a key intermediate for the syntheses of the title natural products in racemic forms.
- Utaka, Masanori,Makino, Hiroshi,Oota, Yukito,Tsuboi, Sadao,Takeda, Akira
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p. 2567 - 2570
(2007/10/02)
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