| 1. |
- Agasti, Soumitra, et al.
(author)
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Palladium-Catalyzed Synthesis of 2,3-Disubstituted Benzofurans : An Approach Towards the Synthesis of Deuterium Labeled Compounds
- 2015
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 357:10, s. 2331-2338
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Journal article (peer-reviewed)abstract
- Palladium-catalyzed oxidative annulations between phenols and alkenylcarboxylic acids produced a library of benzofuran compounds. Depending on the nature of the substitution of the phenol precursor, either 2,3-dialkylbenzofurans or 2-alkyl-3-methylene-2,3-dihydrobenzofurans can be synthesized with excellent regioselectivity. Reactions between conjugated 5-phenylpenta-2,4-dienoic acids and phenol gave 3-alkylidenedihydrobenzofuran alkaloid motifs while biologically active 7-arylbenzofuran derivatives were prepared by starting from 2-phenylphenols. More interestingly, selective incorporation of deuterium from D2O has been discovered, which offers an attractive one-step method to access deuterated compounds.
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| 2. |
- Bah, Juho, et al.
(author)
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Carbocations as Lewis Acid Catalysts : Reactivity and Scope
- 2015
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 357:1, s. 148-158
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Journal article (peer-reviewed)abstract
- One class of potential Lewis acids that has received negligible attention as a catalyst is the carbocation. Here we show the potential of triarylmethylium ions as highly powerful Lewis acid catalysts for organic reactions. The Lewis acidity of the triarylmethylium ion can be easily tuned by variation of the electronic properties of the aromatic rings and the catalytic activity of the carbocation is shown to correlate directly to the level of stabilization of the empty p(C)-orbital at the cationic carbon. The versatility of triarylmethylium ions as efficient Lewis acid catalysts for organic reactions is demonstrated in Diels-Alder, aza-Diels-Alder, conjugate addition, halogenation, epoxide rearrangement and intramolecular hetro-ene reactions.
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| 3. |
- Di Francesco, Davide, et al.
(author)
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Ductile Pd-Catalysed Hydrodearomatization of Phenol-Containing Bio-Oils Into Either Ketones or Alcohols using PMHS and H2O as Hydrogen Source
- 2018
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 360:20, s. 3924-3929
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Journal article (peer-reviewed)abstract
- A series of phenolic bio-oil components were selectively hydrodearomatized by palladium on carbon into the corresponding ketones or alcohols in excellent yields using polymethylhydrosiloxane and water as reducing agent. The selectivity of the reaction was governed by the water concentration where selectivity to alcohol was favoured at higher water concentrations. As phenolic bio-oil examples cardanol and beech wood tar creosote were studied as substrate to the developed reaction conditions. Cardanol was hydrodearomatized into 3-pentadecylcyclohexanone in excellent yield. From beech wood tar creosote, a mixture of cyclohexanols was produced. No hydrodeoxygenation occurred, suggesting the applicability of the reported method for the production of ketone-alcohol oil from biomass.
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| 4. |
- Kohls, Hannes, et al.
(author)
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Selective Access to All Four Diastereomers of a 1,3-Amino Alcohol by Combination of a Keto Reductase- and an Amine Transaminase-Catalysed Reaction
- 2015
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 357:8, s. 1808-1814
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Journal article (peer-reviewed)abstract
- The biocatalytic synthesis of chiral amines has become a valuable addition to the chemists' tool-box. However, the efficient asymmetric synthesis of functionalised amines bearing more than one stereocentre, such as 1,3-amino alcohols, remains challenging. By employing a keto reductase (KRED) and two enantiocomplementary amine transaminases (ATA), we developed a biocatalytic route towards all four diastereomers of 4-amino-1-phenylpentane-2-ol as a representative molecule bearing the 1,3-amino alcohol functionality. Starting from a racemic hydroxy ketone, a kinetic resolution using an (S)-selective KRED provided optically active hydroxy ketone (86% ee) and the corresponding diketone. Further transamination of the hydroxy ketone was performed by either an (R)- or an (S)-selective ATA, yielding the (2R,4R)- and (2R,4S)-1,3-amino alcohol diastereomers. The remaining two diastereomers were accessible in two subsequent asymmetric steps: the diketone was reduced regio- and enantioselectively by the same KRED, which yielded the (S)-configured hydroxy ketone. Eventually, the subsequent transamination of the crude product with (R)- and (S)-selective ATAs yielded the remaining (2S,4R)and (2S,4S)-diastereomers, respectively.
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| 5. |
- Margalef, Jessica, et al.
(author)
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Third-Generation Amino Acid Furanoside-Based Ligands from d-Mannose for the Asymmetric Transfer Hydrogenation of Ketones : Catalysts with an Exceptionally Wide Substrate Scope
- 2016
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 358:24, s. 4006-4018
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Journal article (peer-reviewed)abstract
- A modular ligand library of -amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected -amino acids and three different amino alcohols derived from 2,3-O-isopropylidene--d-mannofuranoside. The ligand library was evaluated in the half-sandwich ruthenium- and rhodium-catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including simple as well as sterically demanding aryl alkyl ketones, aryl fluoroalkyl ketones, heteroaromatic alkyl ketones, aliphatic, conjugated and propargylic ketones. Under the optimized reaction conditions, secondary alcohols were obtained in high yields and in enantioselectivities up to >99%. The choice of ligand/catalyst allowed for the generation of both enantiomers of the secondary alcohols, where the ruthenium-hydroxyamide and the rhodium-thioamide catalysts act complementarily towards each other. The catalytic systems were also evaluated in the tandem isomerization/asymmetric transfer hydrogenation of racemic allylic alcohols to yield enantiomerically enriched saturated secondary alcohols in up to 98% ee. Furthermore, the catalytic tandem -alkylation/asymmetric transfer hydrogenation of acetophenones and 3-acetylpyridine with primary alcohols as alkylating and reducing agents was studied. Secondary alcohols containing an elongated alkyl chain were obtained in up to 92% ee.
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| 6. |
- Marx, Lisa, et al.
(author)
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Chemoenzymatic Approaches to the Synthesis of the Calcimimetic Agent Cinacalcet Employing Transaminases and Ketoreductases
- 2018
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In: Advanced Synthesis and Catalysis. - : Wiley-VCH Verlagsgesellschaft. - 1615-4150 .- 1615-4169. ; 360:11, s. 2157-2165
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Journal article (peer-reviewed)abstract
- Abstract Several chemoenzymatic routes have been explored for the preparation of cinacalcet, a calcimimetic agent. Transaminases (TAs) and ketoreductases (KREDs) turned out to be useful biocatalysts for the preparation of key optically active precursors. Thus, the asymmetric amination of 1â€acetonaphthone yielded an enantiopure (R)â€amine, which can be alkylated in one step to yield cinacalcet. Alternatively, the bioreduction of the same ketone resulted in an enantiopure (S)â€alcohol, which was easily converted into the previous (R)â€amine. In addition, the reduction was efficiently performed with the KRED and its cofactor coâ€immobilized on the same porous surface. This selfâ€sufficient heterogeneous biocatalyst presented an accumulated total turnover number (TTN) for the cofactor of 675 after 5 consecutive operational cycles. Finally, in a preparative scale synthesis the TAâ€based approach was performed in aqueous medium and led to enantiopure cinacalcet in two steps and 50% overall yield.
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| 7. |
- Mishra, Abhishek Kumar, et al.
(author)
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Catalytic O- to N-Alkyl Migratory Rearrangement : Transition Metal-Free Direct and Tandem Routes to N-Alkylated Pyridones and Benzothiazolones
- 2018
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In: Advanced Synthesis and Catalysis. - : WILEY-V C H VERLAG GMBH. - 1615-4150 .- 1615-4169. ; 360:20, s. 3930-3939
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Journal article (peer-reviewed)abstract
- The present study reports the synthesis of N-alkylated pyridones and benzothiazolones via O- to N-alkyl group migration under transition metal-free TfOH-catalyzed reaction conditions for the first time, to the best of our knowledge. Primary as well as secondary alkyl groups smoothly migrate under the present reaction conditions. Moreover, a minor modification of the protocol used in this study is found to be applicable for an entirely new tandem synthesis of 2-alkoxy-N-heterocycles from the simplest starting materials in a solvent-free reaction conditions. Density Functional Theory (DFT) calculation identifies the energy species associated with the rearrangement, whereas, mechanistic experiments explore the role of the catalyst as the alkyl group transfer mediator.
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| 8. |
- Ni, Shengjun, et al.
(author)
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Carbocation Catalyzed Bromination of Alkyl Arenes, a Chemoselective sp3 vs. sp2 C−H Functionalization
- 2018
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In: Advanced Synthesis and Catalysis. - : Wiley-VCH Verlagsgesellschaft. - 1615-4150 .- 1615-4169. ; 360:21, s. 4197-4204
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Journal article (peer-reviewed)abstract
- The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst isdemonstrated in a light induced benzylic brominaion of alkyl-arenes under mild conditions. The reaction wasconducted at ambient temperature under common hood light (55 W fluorescent light) with catalyst loadingsdown to 2.0 mol% using N-bromosuccinimide (NBS) as the brominating agent. The protocol is applicable toan extensive number of substrates to give benzyl bromides in good to excellent yields. In contrast to mostpreviously reported strategies, this protocol does not require any radical initiator or extensive heating. Forelectron-rich alkyl-arenes, the trityl ion catalyzed bromination could be easily switched between benzylic sp3CH functionalization and arene sp2 CH functionalization by simply alternating the solvent. Thischemoselective switch allows for high substrate control and easy preparation of benzyl bromides andbromoarenes, respectively. The chemoselective switch was also applied in a one-pot reaction of 1-methylnaphthalene for direct introduction of both sp3 CBr and sp2 CBr functionality.
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| 9. |
- Pàmies, Oscar, et al.
(author)
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Artificial Metalloenzymes in Asymmetric Catalysis : Key Developments and Future Directions
- 2015
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 357:8, s. 1567-1586
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Research review (peer-reviewed)abstract
- Artificial metalloenzymes combine the excellent selective recognition/binding properties of enzymes with transition metal catalysts, and therefore many asymmetric transformations can benefit from these entities. The search for new successful strategies in the construction of metal-enzyme hybrid catalysts has therefore become a very active area of research. This review discusses all the developed strategies and the latest advances in the synthesis and application in asymmetric catalysis of artificial metalloenzymes with future directions for their design, synthesis and application (Sections 2-4). Finally, advice is presented (to the non-specialist) on how to prepare and use artificial metalloenzymes (Section 5).
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| 10. |
- Payer, Stefan E., et al.
(author)
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Exploring the Catalytic Promiscuity of Phenolic Acid Decarboxylases : Asymmetric, 1,6-Conjugate Addition of Nucleophiles Across 4-Hydroxystyrene
- 2017
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 359:12, s. 2066-2075
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Journal article (peer-reviewed)abstract
- The catalytic promiscuity of a ferulic acid decarboxylase from Enterobacter sp. (FDC_Es) and phenolic acid decarboxylases (PADs) for the asymmetric conjugate addition of water across the C=C bond of hydroxystyrenes was extended to the N-, C-and S-nucleophiles methoxyamine, cyanide and propanethiol to furnish the corresponding addition products in up to 91% ee. The products obtained from the biotransformation employing the most suitable enzyme/nucleophile pairs were isolated and characterized after optimizing the reaction conditions. Finally, a mechanistic rationale supported by quantum mechanical calculations for the highly (S)selective addition of cyanide is proposed.
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