| 1. |
- Adeyemi, Ahmed, et al.
(författare)
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Regio- and Stereoselective Synthesis of Allylic Spiroethers (Spirobenzofuranes) via an Intramolecular Mizoroki-Heck Reaction
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:12, s. 7648-7657
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Tidskriftsartikel (refereegranskat)abstract
- The palladium(0)-catalyzed intramolecular annulation of 12 1,3-disubstituted cyclopentenes, derived from (+)-vincelactam, resulted in 5-exo cyclizations which furnished a series of 2,5-dimethyl-14(3R,4'S)-2H-spiro[benzofuran-3,1'-cyclopentan]2'-en-4'-yl)-1H-pyrroles in excellent diastereoselectivities and useful isolated yields. The double bond migration process that followed the arylpalladium insertion was controlled by a fine-tuning of the reaction system, which provided regioselectivities of up to 98:2. The selective Mizoroki-Heck reaction was used as the key transformation for preparing two new spirocyclic monoprotected amino acids as single stereoisomers.
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| 2. |
- Adolfsson, Dan E., 1989-, et al.
(författare)
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Intramolecular Povarov Reactions for the Synthesis of Chromenopyridine fused 2-Pyridone Polyheterocycles Binding to α-Synuclein and Amyloid-β fibrils
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:21, s. 14174-14189
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A BF3×OEt2 catalyzed intramolecular Povarov reaction was used to synthesize a library of 15 chromenopyridine fused thiazolino-2-pyridone peptidomimetics. The reaction works with a range of O-alkylated salicylaldehydes and amino functionalized thiazolino-2-pyridones, to generate polyheterocycles with diverse substitution. The synthesized compounds were screened for their ability to bind α-synuclein and amyloid β fibrils in vitro. Analogs substituted with a nitro group bind to mature amyloid fibrils, and the activity moreover depends on the positioning of this functional group.
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| 3. |
- Azzi, Emanuele, et al.
(författare)
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Visible Light Mediated Photocatalytic N‑Radical Cascade Reactivity of γ,δ-Unsaturated N‑Arylsulfonylhydrazones : A General Approach to Structurally Diverse Tetrahydropyridazines
- 2021
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 86:4, s. 3300-3323
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Tidskriftsartikel (refereegranskat)abstract
- Tetrahydropyridazines are of particular interest for their versatility as intermediates in organic synthesis and display pharmacological activity in several domains. Here, we describe the photocatalytic synthesis of different tetrahydropyridazines starting from gamma,delta-unsaturated N-arylsulfonylhydrazones. Simple structural changes of substrates result into three different pathways beginning from a common N-hydrazonyl radical, which evolves through a domino carboamination/dearomatization, a HAT process, or a photoinduced radical Smiles rearrangement to afford diverse tetrahydropyridazines. All reactions are carried out in very mild conditions, and the quite inexpensive [Ru(bpy)(3)]Cl-2 is used as the catalyst. Preliminary mechanism studies are presented, among them luminescence and electrochemical characterization of the involved species. Computational studies allow to rationalize the mechanism in accord with the experimental findings.
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| 4. |
- Baumruck, A. C., et al.
(författare)
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Native Chemical Ligation of Highly Hydrophobic Peptides in Ionic Liquid-Containing Media
- 2021
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 86:2, s. 1659-1666
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Tidskriftsartikel (refereegranskat)abstract
- The chemical synthesis of a highly hydrophobic membrane-associated peptide by native chemical ligation (NCL) in an ionic liquid (IL) [C2mim][OAc]/buffer mixture was achieved by employing peptide concentrations up to 11 mM. NCL was studied at different pH and water content and compared to several "gold-standard"ligation protocols. The optimized reaction protocol for the NCL in IL required the addition of 40% water and pH adjustment to 7.0-7.5, resulting in ligation yields of up to 80-95% within 1 to 4 h. This new ligation protocol is generally applicable and outperforms current "gold-standard"NCL methods. ©
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| 5. |
- Biosca, Maria, et al.
(författare)
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Mechanism of Asymmetric Homologation of Alkenylboronic Acids with CF3-Diazomethane via Borotropic Rearrangement
- 2024
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Ingår i: Journal of Organic Chemistry. - 0022-3263 .- 1520-6904. ; 89:7, s. 4538-4548
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations have been performed to investigate the mechanism for the BINOL-catalyzed asymmetric homologation of alkenylboronic acids with CF3-diazomethane. The reaction proceeds via a chiral BINOL ester of the alkenylboronic acid substrate. The calculations reveal a complex scenario for the formation of the chiral BINOL-alkenylboronate species, which is the key intermediate in the catalytic process. The aliphatic alcohol additive plays an important role in the reaction. This study provides a rationalization of the stereoinduction step of the reaction, and the enantioselectivity is mainly attributed to the steric repulsion between the CF3 group of the diazomethane reagent and the γ-substituent of the BINOL catalyst. The complex potential energy surface obtained by the calculations is analyzed by means of microkinetic simulations.
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| 6. |
- Brea, Oriana, et al.
(författare)
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Mechanisms of Formation and Rearrangement of Benziodoxole-Based CF3 and SCF3 Transfer Reagents
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:23, s. 15577-15585
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Tidskriftsartikel (refereegranskat)abstract
- Togni's benziodoxole-based reagents are widely used in trifluoromethylation reactions. It has been established that the kinetically stable hypervalent iodine form (I-CF3) of the reagents is thermodynamically less stable than its acyclic ether isomer (O-CF3). On the other hand, the trifluoromethylthio analogue exists in the thermodynamically stable thioperoxide form (O-SCF3), and the hypervalent form (I-SCF3) has been elusive. Despite the importance of these reagents, very little is known about the reaction mechanisms of their syntheses, which has hampered the development of new reagents of the same family. Herein, we use density functional theory calculations to understand the reasons for the divergent behaviors between the CF3 and SCF3 reagents. We demonstrate that they follow different mechanisms of formation and that the metals involved in the syntheses (potassium in the case of the trifluoromethyl reagent and silver in the trifluoromethylthio analogue) play key roles in the mechanisms and greatly influence the possibility of their rearrangements from the hypervalent (I-CF3, I-SCF3) to the corresponding ether-type form (O-CF3, O-SCF3).
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| 7. |
- Burke, Anthony, et al.
(författare)
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Recent Advances in Asymmetric Hydrogenation Catalysis Utilizing Spiro and Other Rigid C-Stereogenic Phosphine Ligands
- 2022
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society. - 0022-3263 .- 1520-6904. ; 87:4, s. 1898-1924
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Tidskriftsartikel (refereegranskat)abstract
- Transition-metal-catalyzed asymmetric reactions have been a powerful tool in organic synthesis for many years. The design of chiral ligands with the right configuration is fundamental to induce high regio- and stereoselectivity to catalytic reactions and to achieve high turnover numbers and high yields. A challenge is the control of prochiral centers with similar electronic properties in a similar steric environment within the same molecule. Over the last 10 years, a range of novel rigid C-stereogenic chiral phosphine ligands has been developed and successfully applied in various types of asymmetric transformations. Many of these ligands are of a di-, tri-, or multidentate nature. The purpose of this Perspective is to highlight recent synthetic achievements (since 2010) with spiro-phosphines and other rigid phosphines and discuss some mechanistic aspects of the catalytic reactions.
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| 8. |
- Cao, Guanyue, et al.
(författare)
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Porphyrindiene-Based Tandem Diels-Alder Reaction for Preparing Low-Symmetry pi-Extended Porphyrins with Push-Pull Skeletons
- 2022
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Ingår i: Journal of Organic Chemistry. - : AMER CHEMICAL SOC. - 0022-3263 .- 1520-6904. ; 87:14, s. 9001-9010
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Tidskriftsartikel (refereegranskat)abstract
- Tandem Diels-Alder reactions of masked porphyrindienes (i.e., sulfolenoporphyrins) with benzoquinones and stilbenes, followed by aromatization, have been developed to load porphyrin with mixed annulation units (i.e., terphenyl and naphthoquinone), furnishing the low-symmetry pi-extended porphyrins (DxAy) with push-pull skeletons. All low-symmetrical chromophores display panchromatic absorption spectra, which look like a spectral combination of symmetrical congeners (D4/A4) in a certain ratio. Among them, tD2A2 with trans-arrangement of push/pull units possesses the largest maximum centered at 766 nm with the onset around 900 nm. The fusion of the electron-deficient naphthoquinone moiety on the porphyrin core results in the approximately quantitative regulation of the E-ox1 and HOMOs (i.e., 0.10-0.13 V increase for the E-ox1 and 0.14-0.16 eV decrease for the HOMOs per naphthoquinone unit). In brief, this work provides a new way to construct low-symmetry pi-extended porphyrins with tunable properties resorting to the ratios and locations of the annulated push-pull units.
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| 9. |
- Carreiro, Elisabete P., et al.
(författare)
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Asymmetric Additions Empowered by OrganoCatalysts, Metal Catalysts, and Deep Natural Eutectic Solvents (NADES)
- 2024
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society. - 0022-3263 .- 1520-6904. ; 89, s. 6631-
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Tidskriftsartikel (refereegranskat)abstract
- This article is a history of an industrial-academic partnership that started almost two decades ago and details the evolution of a relationship between a small academic research group and a spin-out company located in Portugal. Their activities have ranged from the development of new metal-based catalytic systems for asymmetric epoxidations, allylic alkylations, and arylations to the development of novel cinchona-based organocatalysts for asymmetric hydrosilylations and Michael additions. Current common interests are centered on the development of novel chiral Natural Deep Eutectic Solvent systems, which they are investigating in different types of reaction systems.
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| 10. |
- Dunås, Petter, 1990, et al.
(författare)
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Azulene functionalization by iron-mediated addition to a cyclohexadiene scaffold
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:21, s. 13453-16465
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Tidskriftsartikel (refereegranskat)abstract
- The functionalization of azulenes via reaction with cationic η5-iron carbonyl diene complexes under mild reaction conditions is demonstrated. A range of azulenes, including derivatives of naturally occurring guaiazulene, were investigated in reactions with three electrophilic iron complexes of varying electronic properties, affording the desired coupling products in 43−98% yield. The products were examined with UV− vis/fluorescence spectroscopy and showed interesting halochromic properties. Decomplexation and further derivatization of the products provide access to several different classes of 1-substituted azulenes, including a conjugated ketone and a fused tetracycle.
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