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| 2. |
- Fardost, Ashkan, et al.
(författare)
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A non-resonant microwave applicator fully dedicated to continuous flow chemistry
- 2012
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Ingår i: Chimica oggi. - 0392-839X .- 1973-8250. ; 30:4, s. 14-16
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Tidskriftsartikel (refereegranskat)abstract
- The concept of a non-resonant microwave applicator designed for continuous flow chemistry was introduced by our group this year. With a power output of 0 - 150 W, adjustable frequency range of 2.4 - 2.5 GHz and five IR sensors monitoring the temperature along a tubular borosilicate reactor, the instrument ensures fast, efficient and uniform heating. A variety of organic reactions were optimized for continuous flow chemistry using a 200 mm x empty set 3 mm reactor, which proved the instrument to be an unprecedented tool for fast method optimization. A scale-out study is now reported where reactions already optimized in a empty set 3 mm reactor are run in a empty set 6 mm reactor, aiming for a fourfold increase in chemical throughput with no or little need for re-optimization.
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| 3. |
- Fardost, Ashkan, et al.
(författare)
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Palladium(II)-Catalyzed Decarboxylative Heck Arylations of Acyclic Electron-Rich Olefins with Internal Selectivity
- 2014
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 356:4, s. 870-878
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Tidskriftsartikel (refereegranskat)abstract
- Despite the recent emergence of decarboxylative CC bond forming reactions, methodologies providing internally arylated electron-rich olefins are still lacking. We herein report on palladium(II)-catalyzed decarboxylative Heck arylations of linear electron-rich olefins with excellent selectivity for the internal position. The method allows a variety of electron-rich linear olefins to undergo arylation with ortho-functionalized aromatic carboxylic acids, including heterocycles. The reaction mechanism has been explored with ESI-MS studies to confirm previous findings, and to reveal the formation of a highly stable palladium complex as a result of the Heck product reacting with the catalyst.
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| 4. |
- Fardost, Ashkan, 1985-
(författare)
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Palladium(II)-Catalyzed Heck Reactions : Domino Reactions, Decarboxylations, Mechanistic Studies & Continuous Flow Applications
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes research efforts dedicated to the development of palladium(II)-catalyzed oxidative Heck and Heck/Suzuki domino reactions, and the applications of a new microwave heating technology, purpose-built for continuous flow in organic synthesis.Paper I describes the development of a ligand-modulated approach for attaching aryl groups to a chelating vinyl ether. By switching the ligand being used, selectivity for the arylation could be shifted to obtain three different outcomes: internal α- or terminal β-arylation, as well as a serendipitously discovered domino α,β-diarylation process. The latter was proposed to be an effect of para-benzoquinone, effectively acting as a stabilizing π-acidic ligand with the ability to suppress β-hydride elimination.Paper II explores the performance of a new microwave heating technology in combination with continuous flow. The novel nonresonant microwave applicator allowed rapid heating of common laboratory solvents and reaction mixtures above their boiling points with stable and reproducible temperature profiles. The technology was successfully applied to small-scale method development and subsequent scale-out of palladium-catalyzed reactions, heterocycle synthesis and classical organic transformations such as the Fischer indole synthesis.Paper III focuses on developing regioselective oxidative decarboxylative Heck reactions with electron-rich olefins. Successful internal α-arylations were achieved using various olefins and ortho-substituted aromatic acids. The mechanism was also studied by ESI-MS analysis. Key cationic organopalladium intermediates were identified, as well as an unexpected palladium(II)-complex which was isolated and characterized. Its experimentally deduced structure was in accordance with the lowest energy minimum found by DFT calculations. Preliminary findings suggested that the complex acts as a catalyst trap.Paper IV studies the mechanism of the reaction in Paper III by means of DFT calculations. Reductive elimination was identified as the rate-determining step when using a linear enamide as the olefin, due to its propensity to form low energy chelates. Its chelating properties also played a key role in the stability of the isolated palladium(II)-complex. The complex, which can act as a catalyst trap, was characterized by X-ray crystallography.
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| 5. |
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| 6. |
- Lindh, Jonas, et al.
(författare)
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Convenient Stille carbonylative cross-couplings using molybdenum hexacarbonyl
- 2010
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Ingår i: Tetrahedron Letters. - : Elsevier BV. - 0040-4039 .- 1359-8562. ; 51:18, s. 2470-2472
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Tidskriftsartikel (refereegranskat)abstract
- Palladium catalysis was used in Stille-type carbonylative cross-couplings employing Mo(CO)(6) as the carbon monoxide source. Robust and convenient transformations were carried out in closed vessels at 100 degrees C, providing a set of diaryl ketones in good yields. Aryl triflates and bromides were used as coupling partners with aryl stannanes. Inclusion of the Mo(CO)(6) destabilizing agent DBU made this protocol operationally simple and suppressed side-product formation. (C) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
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| 8. |
- Trejos, Alejandro, et al.
(författare)
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Palladium(II)-catalyzed coupling reactions with a chelating vinyl ether and arylboronic acids : a new Heck/Suzuki domino diarylation reaction
- 2009
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 48, s. 7587-7589
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Tidskriftsartikel (refereegranskat)abstract
- A mild and novel palladium(II)-catalyzed domino Heck/Suzuki alpha,beta-diarylation-reduction of a dimethylaminoethyl substituted chelating vinyl ether was developed by using electron-rich arylboronic acids in combination with p-benzoquinone. Based on the preparative results, a catalytic cycle is proposed. Further, highly regioselective palladium(II)-catalyzed alpha- or beta-monoarylation of the chelating vinyl ether was achieved using either a bidentate ligand or by employing ligand-less conditions.
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| 9. |
- Yahiaoui, Samir, et al.
(författare)
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Chelation-Mediated Palladium(II)-Catalyzed Domino Heck-Mizoroki/Suzuki-Miyaura Reactions Using Arylboronic Acids : Increasing Scope and Mechanistic Understanding
- 2011
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:8, s. 2433-2438
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Tidskriftsartikel (refereegranskat)abstract
- A palladium(II)-catalyzed Heck-Mizoroki/Suzuki-Miyaura domino reaction involving metal coordinating dimethylaminoethyl vinyl ethers and a number of electron-rich and electron-deficient arylboronic acids has been developed. Through variation of the temperature and the concentration of the p-benzoquinone (p-Bq) ligand/reoxidant, conditions for the robust and convenient one-pot generation of diarylated-saturated ethers were identified. With the aid of coordination of the dimethylamino group to the arylpalladium intermediate, the otherwise predominant formation of the beta-arylated olefin could be reversed. A reaction route involving a chelation-controlled carbopalladation, providing a p-Bq stabilized six-membered palladacycle, followed by transmetalation and reductive elimination is suggested to explain the selective formation of saturated diarylated ether products.
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| 10. |
- Öhrngren, Per, et al.
(författare)
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Evaluation of a Nonresonant Microwave Applicator for Continuous-Flow Chemistry Applications
- 2012
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Ingår i: Organic Process Research & Development. - : American Chemical Society (ACS). - 1083-6160 .- 1520-586X. ; 16:5, s. 1053-1063
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Tidskriftsartikel (refereegranskat)abstract
- The concept of a nonresonant microwave applicator for continuous-flow organic chemistry is introduced and evaluated. The frequency of the incident microwave radiation can be adjusted between 2.4 and 2.5 GHz to optimize the energy absorbance. The temperature of the reaction is monitored by five IR sensors, and their signals can be used to automatically adjust the power output from the microwave generator. The heating of several different solvents up to 20 degrees C above the standard boiling point has been explored. Several different organic reactions have been successfully carried out using a 200 mm X (sic) 3 mm tubular borosilicate reactor and a flow between 47 and 2120 mu L/min. The microwave heating pattern was visualized with an IR camera. The transformations include palladium-catalyzed coupling reactions (oxidative Heck and Suzuki reactions), heterocyclic chemistry (oxathiazolone and Fischer indole synthesis), rearrangement (Claisen), and a Diels-Alder cycloaddition reaction. A scale-out to 57 mmol/h was performed with the Fischer indole reaction.
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