| 1. |
- Adeyemi, Ahmed, et al.
(författare)
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Continuous Flow Synthesis under High-Temperature/High-Pressure Conditions Using a Resistively Heated Flow Reactor
- 2017
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Ingår i: Organic Process Research & Development. - : AMER CHEMICAL SOC. - 1083-6160 .- 1520-586X. ; 21:7, s. 947-955
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Tidskriftsartikel (refereegranskat)abstract
- A cheap, easy-to-build, and effective resistively heated reactor for continuous flow synthesis at high temperature and pressure is herein presented. The reactor is rapidly heated directly using, an electric current and is capable of rapidly delivering temperatures and pressures up to 400 degrees C and 200 bar, respectively. High-temperature and high-pressure applications of this reactor were safely performed and demonstrated by selected transformations such as esterifications, transesterifications, and direct carboxylic acid to nitrile reactions using supercritical ethanol, methanol, and acetonitrile. Reaction temperatures were between 300 and 400 degrees C with excellent conversions and good to excellent isolated product yields. Examples of Diels-Alder reactions were also carried out at temperatures up to 300 degrees C in high yield. No additives or catalysts were used in the reactions.
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| 2. |
- Andaloussi, Mounir, et al.
(författare)
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Microwave-promoted palladium(II)-catalyzed C-P bond formation by using arylboronic acids or aryltrifluoroborates.
- 2009
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Ingår i: Chemistry - A European Journal. - Weinheim : Wiley-VCH Verlag GmbH. - 0947-6539 .- 1521-3765. ; 15:47, s. 13069-13074
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Tidskriftsartikel (refereegranskat)abstract
- The first Pd-II-catalyzed P arylation has been performed by using palladium acetate, the rigid bidentate ligand dmphen (dmphen=2,9-dimethyl-1,10-phenanthroline), and without the addition of base or acid. Couplings of arylboronic acids or aryl trifluoroborates with H-phosphonate dialkyl esters were conducted in 30 min with controlled microwave (MW) heating under non-inert conditions. Aryl phosphites were also synthesized at room temperature with atmospheric air as the sole reoxidant. The arylated phosphonates were isolated in 44-90% yields. The excellent chemoselectivity of the method was illustrated in the synthesis of a Mycobacterium tuberculosis glutamine synthetase (MTB-GS) inhibitor. Online ESIMS was used to detect cationic palladium species in ongoing reactions directly, and a catalytic cycle has been proposed based on these results.
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| 3. |
- Axelsson, Linda, et al.
(författare)
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An Improved Palladium(II)-Catalyzed Method for the Synthesis of Aryl Ketones from Aryl Carboxylic Acids and Organonitriles
- 2014
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Ingår i: Tetrahedron Letters. - : Elsevier BV. - 0040-4039 .- 1359-8562. ; 55:15, s. 2376-2380
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Tidskriftsartikel (refereegranskat)abstract
- A palladium(II)-catalyzed decarboxylative protocol for the synthesis of aryl ketones has been developed. The addition of TFA was shown to improve the reaction yield and employing THF as solvent enabled the use of solid nitriles and in only a small excess. Using this method, five different benzoic acids reacted with a wide range of nitriles to produce 29 diverse (hetero)aryl ketone derivatives in up to 94% yield.
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| 4. |
- Konda, Vivek, et al.
(författare)
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Safe Palladium-Catalyzed Cross-Couplings with Microwave Heating Using Continuous-Flow Silicon Carbide Reactors
- 2014
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Ingår i: Organic Process Research & Development. - : American Chemical Society (ACS). - 1083-6160 .- 1520-586X. ; 18:11, s. 1413-1418
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Tidskriftsartikel (refereegranskat)abstract
- Herein we present a 200 mm × 3 mm Øi silicon carbide (SiC) tube reactor for use in a commercially available microwave heated continuous-flow system. The SiC flow reactor enables palladium(0)-catalyzed reactions that, due to precipitation and subsequent hot spot formation, often followed by reactor failure, are unsuitable to conduct in standard microwave-transparent borosilicate glass reactors. We report continuous-flow protocols for the Mizoroki–Heck reaction (10 examples, 81–86% yield) as well as the Suzuki–Miyaura cross-coupling (14 examples, 70–87% yield), showing the utility of the SiC reactor. Furthermore, we performed a scale-out of the NSAID biphenylacetic acid, achieving outputs of 14 mmol/h of the Suzuki–Miyaura reaction, and a 72% overall yield over three steps. The SiC reactor enabled fast and efficient temperature control, high robustness, and easy maintenance.
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| 5. |
- Lindh, Jonas, et al.
(författare)
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Synthesis of styrenes by palladium(II)-catalyzed vinylation of arylboronic acids and aryltrifluoroborates by using vinyl acetate
- 2009
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 15:18, s. 4630-4636
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of aromatic and heteroaromatic boronic acids or aryltrifluoroborate salts with vinyl acetate in the presence of a palladium(II) catalyst give the corresponding styrenes in good yields. This Heck reaction proceeds with microwave heating in less than 30 min at 140 degrees C in the absence of base and tolerates a variety of substituents. No palladium reoxidant is needed and the vinylation is performed under non-inert conditions. Mass spectrometry (electrospray ionization mass spectrometry (ESIMS) and tandem mass spectrometry (MS/MS)) was used to identify cationic palladium-containing complexes in ongoing reactions. The key intermediates that have been detected, together with experiments that used deuterated vinyl acetate, support the existence of catalytically active palladium hydride species, and that it is the arylation of ethylene, not vinyl acetate, which generates the styrene product. The mechanism of the reaction is discussed in terms of the palladium(II) intermediates mentioned above.
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| 6. |
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| 7. |
- Roy, Tamal, et al.
(författare)
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Selective Synthesis of Spirooxindoles by an Intramolecular Heck-Mizoroki Reaction
- 2017
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Ingår i: Organic Letters. - : AMER CHEMICAL SOC. - 1523-7060 .- 1523-7052. ; 19:10, s. 2738-2741
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Tidskriftsartikel (refereegranskat)abstract
- We report a highly diastereoselective synthesis of cydopentene-spirooxindole derivatives via an intramolecular Heck-Mizoroki reaction using aryl bromides as precursors. The reactions were performed under dry conditions or in a DMF-water system. This protocol can be useful to introduce several functionalities to the aromatic nucleus of the spirooxindoles. DFT calculations were performed to rationalize the high antiselectivity. A functionalized spiroproduct was transformed into a cyclic amino acid derivative.
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| 8. |
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| 9. |
- Rydfjord, Jonas, et al.
(författare)
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Decarboxylative Palladium(II)-Catalyzed Synthesis of Aryl Amidines from Aryl Carboxylic Acids : Development and Mechanistic Investigation
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:41, s. 13803-13810
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Tidskriftsartikel (refereegranskat)abstract
- A fast and convenient synthesis of aryl amidines starting from carboxylic acids and cyanamides is reported. The reaction was achieved by palladium(II)-catalysis in a one-step microwave protocol using [Pd(O2CCF3)(2)], 6-methyl-2,2-bipyridyl and trifluoroacetic acid (TFA) in N-methylpyrrolidinone (NMP), providing the corresponding aryl amidines in moderate to excellent yields. The protocol is very robust with regards to the cyanamide coupling partner but requires electron-rich ortho-substituted aryl carboxylic acids. Mechanistic insight was provided by a DFT investigation and direct ESI-MS studies of the reaction. The results of the DFT study correlated well with the experimental findings and, together with the ESI-MS study, support the suggested mechanism. Furthermore, a scale-out (scale-up) was performed with a non-resonant microwave continuous-flow system, achieving a maximum throughput of 11mmolh(-1) by using a glass reactor with an inner diameter of 3mm at a flow rate of 1mLmin(-1).
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| 10. |
- Rydfjord, Jonas, et al.
(författare)
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Temperature measurements with two different IR sensors in a continuous-flow microwave heated system
- 2013
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 9, s. 2079-2087
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Tidskriftsartikel (refereegranskat)abstract
- In a continuous-flow system equipped with a nonresonant microwave applicator we have investigated how to best assess the actual temperature of microwave heated organic solvents with different characteristics. This is non-trivial as the electromagnetic field will influence most traditional methods of temperature measurement. Thus, we used a microwave transparent fiber optic probe, capable of measuring the temperature inside the reactor, and investigated two different IR sensors as non-contact alternatives to the internal probe. IR sensor 1 measures the temperature on the outside of the reactor whilst IR sensor 2 is designed to measure the temperature of the fluid through the borosilicate glass that constitutes the reactor wall. We have also, in addition to the characterization of the before mentioned IR sensors, developed statistical models to correlate the IR sensor reading to a correct value of the inner temperature (as determined by the internal fiber optic probe), thereby providing a non-contact, indirect, temperature assessment of the heated solvent. The accuracy achieved with these models lie well within the range desired for most synthetic chemistry applications.
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