- Synthesis of a polymer-bound iron Lewis acid and its utilization in Diels-Alder reactions
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The first polymer-bound iron Lewis acid 3 was synthesized in two steps from (η5-vinylcyclopentadienyl)dicarbonylmethyliron. Preliminary studies for catalysis of Diels-Alder reactions by the polymer-bound iron Lewis acid 3 are also reported.
- Saha, Anjan K.,Hossain, M. Mahmun
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- STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
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Lewis acidic metal-organic framework (MOF) materials comprising triflate-coordinated metal nodes are described. The materials can be used as heterogenous catalysts in a wide range of organic group transformations, including Diels-Alder reactions, epoxide-ring opening reactions, Friedel-Crafts acylation reactions and alkene hydroalkoxylation reactions. The MOFs can also be prepared with metallated organic bridging ligands to provide heterogenous catalysts for tandem reactions and/or prepared as composites with support particles for use in columns of continuous flow reactor systems. Methods of preparing and using the MOF materials and their composites are also described.
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Paragraph 0186-0188; 0197; 0239; 0249
(2021/02/26)
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- Methods for preparing benzene-ring-containing compounds from pinacol
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The invention relates to methods for preparing durene, 1,2,3-trimethylbenzene, o-xylene, pyromellitic acid and trimellitic acid from pinacol. Durene, 1,2,3-trimethylbenzene and o-xylene are prepared through three steps of reaction, and pyromellitic acid and trimellitic acid are prepared through four steps of reaction. A catalytic system used in the invention is green and environment-friendly, andcan be recycled. The raw materials of method, i.e., pinacol, crotonaldehyde, acrolein and crotonate can all be derived from biomass, and are cheap and easily available. All the reaction processes aresimple and are high in activity and selectivity in the dehydration of pinacol and the dehydrogenation, decarbonylation and oxidation of D-A products. The invention provides novel methods for preparingfine chemicals including durene, 1,2,3-trimethylbenzene, o-xylene, pyromellitic acid and trimellitic acid from lignocellulose-based platform chemicals.
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- Carbocations as lewis acid catalysts in diels-alder and Michael addition reactions
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In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction. Copyright
- Bah, Juho,Franzen, Johan
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p. 1066 - 1072
(2014/02/14)
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- Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction
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A one-pot procedure is described for using α,β-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no electron-with-drawing substituents. In this way, the aldehyde group serves as a traceless control element to direct the cycloaddition reaction. The Diels-Alder reactions are performed in a diglyme solution in the presence of a catalytic amount of boron trifluoride etherate. Subsequent quenching of the Lewis acid, addition of 0.3% of [Rh(dppp)2Cl] and heating to reflux achieves the ensuing decarbonylation to afford the product cyclohexenes. Under these conditions, acrolein, crotonaldehyde and cinnamaldehyde have been reacted with a variety of 1,3-dienes to afford cyclohexenes in overall yields between 53 and 88%. In these transformations, the three aldehydes serve as equivalents of ethylene, propylene and styrene, respectively.
- Taarning, Esben,Madsen, Robert
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supporting information; experimental part
p. 5638 - 5644
(2009/05/30)
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- EFFICIENT CYCLOADDITION DURING ADSORPTION ON CHROMATOGRAPHIC SOLVENTS
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An essentially new method was developed for carrying out cycloaddition on the surface of chromatographic adsorbents in the absence of solvent.This method permits the use of much milder reaction conditions and to increase the reaction's selectivity.
- Veselovskii, V. V.,Gybin, A. S.,Lozanova, A. V.,Moiseenkov, A. M.,Smit, V. A.
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- DRAMATIC ACCELERATION OF THE DIELS-ALDER REACTION BY ADSORPTION ON CHROMATOGRAPHY ADSORBENTS
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The development of a new method for effecting cycloadditions on the surface of chromatographic adsorbents in the absence of solvents that leads to a moderation of the reaction conditions and an increase in selectivity is described.
- Veselovsky, V. V.,Gybin, A. S.,Lozanova, A. V.,Moiseenkov, A. M.,Smit, W. A.,Caple, R.
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p. 175 - 178
(2007/10/02)
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- A New Total Synthesis of Epifenchone and Dehydrocamphenilone
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A new and simple method with good yields for the total synthesis of the title substances 5 and 9 is described.Methylation of 3, 4, and 8 with CH3I/LCIA in THF under reflux yields the geminal dimethylnorbornanones 5, 6, and 9.
- Dworan, Erich,Buchbauer, Gerhard
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p. 2357 - 2359
(2007/10/02)
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- Relationships between structure of some cyclohexene derivatives and attractiveness for the males of Ceratitis capitata
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Derivatives of 3 cyclohexene 1 carboxaldehyde variously substituted with methyl and phenyl groups at the 3, 4 and 6 positions, the corresponding 3 cyclohexene 1 methanol derivatives and their acetates were prepared and the relationships between their structure and their attractiveness for Ceratitis capitata males was investigated. Activity almost disappeared in the alcoholic derivatives, while some of the aldehydes and the acetates showed slight to strong attractiveness. Introduction of methyl or phenyl groups at the 3, 4 and 6 positions caused alteration of activity; the bulky phenyl group at position 6 caused loss of attractiveness in all cases.
- Guiotto,Rodighiero,Fornasiero
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