- Aldol Condensations Catalyzed by Basic Anion-Exchange Resins
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The aldol condensations of various aldehydes with ketones in the presence of anionic (basic) ion-exchange resins have been investigated. Both batch and continuous modes were studied and compared for the reaction of citral (a mixture of geranial and neral) with acetone to give ψ-ionone. Different reaction conditions were investigated, and the performances of five different ion-exchange resins were compared. The most stable resins could be used for 10 cycles in batch mode or 1000 min in continuous mode without a significant loss in activity or selectivity.
- Bonrath, Werner,Pressel, Yann,Schütz, Jan,Ferfecki, Erich,Topp, Klaus-Dieter
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p. 3584 - 3591
(2016/12/14)
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- 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) an efficient homogeneous catalyst for aldol condensation reactions. Study of the catalyst recovery and reusability using CO2
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In this work it was shown that TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene), a cheap and commercially available guanidine base, efficiently catalyzes aldol condensation reactions yielding interesting products for pharmacological and fragrance industries. This methodology works under solvent-less conditions and affords with very good conversions the corresponding products. Moreover, a simple and effective separation protocol using the CO2 fixation was employed. The catalyst could be recovered and re-used for three consecutive runs without significant loss of activity.
- Cota, Iuliana,Medina, Francisco,Sueiras, Jesús E.,Tichit, Didier
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experimental part
p. 385 - 387
(2011/02/28)
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- CONTINUOUS PROCESS FOR PRODUCING PSEUDOIONONES AND IONONES
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The invention relates to a continuous process for producing pseudoionones of general formulas (I) and (I′) as well as isomers thereof, whereby: R1represents CH3 or (a); R2 and R3 represent hydrogen, CH3 or C2H5, and; R4 and R5represent hydrogen or CH3. These pseudoionones are produced by reacting an aldehyde of formula (II) with an excess of a ketone of general formula (III), whereby R1, R2 and R3 have the aforementioned meanings, in the presence of water and alkali hydroxide at an increased temperature and in a homogeneous solution. The inventive process is characterized in that: a) the intermixing of the homogeneous solution consisting of aldehyde, ketone and aqueous alkali lye occurs at a temperature ranging from 10 to 120 °C; b) the undissolved water and alkali hydroxide contained in the reaction mixture are subsequently separated out; c) while avoiding back mixing, the homogeneous reaction mixture is then guided through a reactor, which permits a residence time ranging from 2 to 300 minutes, at a temperature that is 10 to 120 °C higher than the boiling point of the lowest-boiling component and under a vapor pressure p ranging from 106 to 107 Pa; d) the reaction mixture is cooled by expansion; e) ketone is removed from the reaction mixture using vapor flowing in the opposite direction and; f) the raw product is dried and rid from excessive aldehyde and secondary components via a rectification column.
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Page/Page column 8-10
(2008/06/13)
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- Photochemical transformations of terpenoids in the presence of cyclodextrins
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The effect of complexation of terpene compounds with cyclodextrins on photolysis depends on the type of cyclodextrin and on the structure of the initial substrates. In some cases, only a change in the reaction rate is observed; in other cases, the complexation results in allylic rearrangements, hydride and acyl shifts, and cyclization with the formation of four-, five-, and six-membered cycles, whereas only cis-trans isomerization reactions are observed in the absence of complexation.
- Luzina,Tatarova,Korchagina,Salakhutdinov,Barkhash
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p. 183 - 193
(2007/10/03)
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- Preparation of pseudoionones
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A process is provided for the preparation of pseudoionones by the condensation reaction of citral with a ketone in the presence of lithium hydroxide catalyst.
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- Production of α,β-unsaturated ketones
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A process for the production of α,β-unsaturated ketones by reaction of an aldehyde with a ketone in the presence of a catalyst consisting essentially of zinc oxide in the liquid phase. The ketones obtained are suitable in some cases as solvents and in some cases as intermediates for the production of valuable odorants, dyes, plastics and especially natural substances.
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