387827-64-7Relevant articles and documents
Exploiting the Reactivity of Fluorinated 2-Arylpyridines in Pd-Catalyzed C-H Bond Arylation for the Preparation of Bright Emitting Iridium(III) Complexes
Boyaala, Rabab,Peng, Marie,Tai, Wun-Shan,Touzani, Rachid,Roisnel, Thierry,Dorcet, Vincent,Chi, Yun,Guerchais, Véronique,Doucet, Henri,Soulé, Jean-Fran?ois
, p. 13898 - 13911 (2020)
Pd-catalyzed C-H bond arylation applied to 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine (1) and 2-(3,5-difluorophenyl)-5-(trifluoromethyl)pyridine (5) allows the access to two families of Ir(III) complexes, charge-neutral and cationic species. The reaction is regioselective since only the C3- or C4-position of the fluorinated phenyl ring of 1 or 5 is readily functionalized - namely the C-H bond flanked by the two fluorine atoms which is the most acidic - which allows the electronic control of the reactive site. A range of electron-withdrawing (CN, CO2Et, C(O)Me) substituents on the aryl group has been incorporated leading to the pro-ligands (1, Ar-2,4-dFppy; 2, Ar = p-C6H4-CN; 3, Ar = p-C6H4-CO2Et; 4, Ar = p-C6H4-C(O)Me; 5, and Ar-3,5-dFppy; 6, Ar = p-C6H4-CO2Et). The unsubstituted complexes F1/G1 and F1/G5 featuring 1 and 5, respectively, as C^N ligands are used as reference complexes. The families of five charge-neutral [Ir(C^N)2(N^O)] complexes (C^N is 2-(5-aryl-(4,6-difluorophenyl)-5-(trifluoromethyl)pyridinato (F2-F4), and 2-(4-aryl-(3,5-difluorophenyl)-5-(trifluoromethyl)pyridinato (F5-F6), N^O = 2-picolinate) and five cationic [Ir(C^N)2(N^N)]PF6 complexes (N^N = dmbpy is 4,4′-dimethyl-2,2′-bipyridine) (G2-G6) were synthesized, and their structural and photophysical properties were studied with comparison to the unsubstituted analogues used as reference complexes. The appended aryl group provides large steric bulk as the biaryl fragment is twisted as shown by the X-ray crystal structures of F2, F5, F6, G3, and G5. These latter complexes display a wide variety of different Ir···Ir intermetallic distances in crystals, from 8.150 ? up to 15.034 ?. Moreover, the impact on the emission energy is negligible, as a result of the breaking of the conjugation between the two aryl groups. Charge-neutral complexes [Ir(C^N)2(N^O)] (N^O = 2-picolinate) show bright luminescence: F2-F4 (λem = 495-499 nm) are blue-green emitters, whereas F5 and F6 (λem = 537, 544 nm), where the fluorine substituents are located at the C3- and C5-positions, emit in the green region of the visible spectrum. In all cases, a unitary photoluminescence quantum yield is found. The improvement of φ might be explained by an increase of the radiative rate constant due to a higher degree of rigidity of these congested molecules, compared to the unsubstituted complex F1. The same trends are observed for the family of complexes G. Complexes G1-G4 exhibit blue photoluminescence, and G5 and G6 lead to a red-shifted emission band, as also found for the related complexes F5 and F6 due to the similar fluorine substitution pattern. Their emission quantum yields are remarkably high for charged complexes in the CH2Cl2 solution. These results showed that Pd-catalyzed C-H bond arylation is a valuable synthetic approach for designing efficient emitters with tunable photophysical properties.
Twofold Radical-Based Synthesis of N, C-Difunctionalized Bicyclo[1.1.1]pentanes
Anderson, Edward A.,Mousseau, James. J.,Nugent, Jeremy,Owen, Benjamin,Pickford, Helena D.,Smith, Russell C.
supporting information, p. 9729 - 9736 (2021/07/19)
Bicyclo[1.1.1]pentylamines (BCPAs) are of growing importance to the pharmaceutical industry as sp3-rich bioisosteres of anilines and N-tert-butyl groups. Here we report a facile synthesis of 1,3-disubstituted BCPAs using a twofold radical functionalization strategy. Sulfonamidyl radicals, generated through fragmentation of α-iodoaziridines, undergo initial addition to [1.1.1]propellane to afford iodo-BCPAs; the newly formed C-I bond in these products is then functionalized via a silyl-mediated Giese reaction. This chemistry also translates smoothly to 1,3-disubstituted iodo-BCPs. A wide variety of radical acceptors and iodo-BCPAs are accommodated, providing straightforward access to an array of valuable aniline-like isosteres.
Stereoselective Preparation of C-Aryl Glycosides via Visible-Light-Induced Nickel-Catalyzed Reductive Cross-Coupling of Glycosyl Chlorides and Aryl Bromides
Mou, Ze-Dong,Wang, Jia-Xi,Zhang, Xia,Niu, Dawen
supporting information, p. 3025 - 3029 (2021/05/27)
A nickel-catalyzed cross-coupling reaction of glycosyl chlorides with aryl bromides has been developed. The reaction proceeds smoothly under visible-light irradiation and features the use of bench-stable glycosyl chlorides, allowing the highly stereoselective synthesis of C-aryl glycosides. (Figure presented.).
Base-Activated Latent Heteroaromatic Sulfinates as Nucleophilic Coupling Partners in Palladium-Catalyzed Cross-Coupling Reactions
Blakemore, David C.,Cook, Xinlan A. F.,Moses, Ian B.,Pantaine, Lo?c R. E.,Sach, Neal W.,Shavnya, Andre,Willis, Michael C.
, p. 22461 - 22468 (2021/09/09)
Heteroaromatic sulfinates are effective nucleophilic reagents in Pd0-catalyzed cross-coupling reactions with aryl halides. However, metal sulfinate salts can be challenging to purify, solubilize in reaction media, and are not tolerant to multi-step transformations. Here we introduce base-activated, latent sulfinate reagents: β-nitrile and β-ester sulfones. We show that under the cross-coupling conditions, these species generate the sulfinate salt in situ, which then undergo efficient palladium-catalyzed desulfinative cross-coupling with (hetero)aryl bromides to deliver a broad range of biaryls. These latent sulfinate reagents have proven to be stable through multi-step substrate elaboration, and amenable to scale-up.
A Water-Soluble Iridium Photocatalyst for Chemical Modification of Dehydroalanines in Peptides and Proteins
van Lier, Roos C. W.,de Bruijn, A. Dowine,Roelfes, Gerard
supporting information, p. 1430 - 1437 (2020/12/11)
Dehydroalanine (Dha) residues are attractive noncanonical amino acids that occur naturally in ribosomally synthesised and post-translationally modified peptides (RiPPs). Dha residues are attractive targets for selective late-stage modification of these complex biomolecules. In this work, we show the selective photocatalytic modification of dehydroalanine residues in the antimicrobial peptide nisin and in the proteins small ubiquitin-like modifier (SUMO) and superfolder green fluorescent protein (sfGFP). For this purpose, a new water-soluble iridium(III) photoredox catalyst was used. The design and synthesis of this new photocatalyst, [Ir(dF(CF3)ppy)2(dNMe3bpy)]Cl3, is presented. In contrast to commonly used iridium photocatalysts, this complex is highly water soluble and allows peptides and proteins to be modified in water and aqueous solvents under physiologically relevant conditions, with short reaction times and with low reagent and catalyst loadings. This work suggests that photoredox catalysis using this newly designed catalyst is a promising strategy to modify dehydroalanine-containing natural products and thus could have great potential for novel bioconjugation strategies.
Dearomative Photocatalytic Construction of Bridged 1,3-Diazepanes
Dixon, Darren J.,Duarte, Fernanda,Leitch, Jamie A.,Rogova, Tatiana
supporting information, p. 4121 - 4130 (2020/02/05)
The construction of diverse sp3-rich skeletal ring systems is of importance to drug discovery programmes and natural product synthesis. Herein, we report the photocatalytic construction of 2,7-diazabicyclo[3.2.1]octanes (bridged 1,3-diazepanes) via a reductive diversion of the Minisci reaction. The fused tricyclic product is proposed to form via radical addition to the C4 position of 4-substituted quinoline substrates, with subsequent Hantzsch ester-promoted reduction to a dihydropyridine intermediate which undergoes in situ two-electron ring closure to form the bridged diazepane architecture. A wide scope of N-arylimine and quinoline derivatives was demonstrated and good efficiency was observed in the construction of sterically congested all-carbon quaternary centers. Computational and experimental mechanistic studies provided insights into the reaction mechanism and observed regioselectivity/diastereoselectivity.
Anti-Markovnikov Hydroamination of Unactivated Alkenes with Primary Alkyl Amines
Miller, David C.,Ganley, Jacob M.,Musacchio, Andrew J.,Sherwood, Trevor C.,Ewing, William R.,Knowles, Robert R.
supporting information, p. 16590 - 16594 (2019/11/03)
We report here a photocatalytic method for the intermolecular anti-Markovnikov hydroamination of unactivated olefins with primary alkyl amines to selectively furnish secondary amine products. These reactions proceed through aminium radical cation (ARC) intermediates and occur at room temperature under visible light irradiation in the presence of an iridium photocatalyst and an aryl thiol hydrogen atom donor. Despite the presence of excess olefin, high selectivities are observed for secondary over tertiary amine products, even though the secondary amines are established substrates for ARC-based olefin amination under similar conditions.
Photocatalytic Reductive Formation of α-Tertiary Ethers from Ketals
Rossolini, Thomas,Ferko, Branislav,Dixon, Darren J.
supporting information, p. 6668 - 6673 (2019/09/03)
A general photocatalytic reductive strategy for the construction of unsymmetrical α-tertiary dialkyl ethers is reported. By merging Lewis acid-mediated ketal activation and visible-light photocatalytic reduction, in situ-generated α-alkoxy radicals were found to engage in addition reactions with a variety of olefinic partners. Good reaction efficiency is demonstrated with a range of ketals of aromatic and aliphatic ketones. Extension to acetal substrates is also described, demonstrating the overall synthetic utility of this methodology for complex ether synthesis.
Fundamentally Different Distance Dependences of Electron-Transfer Rates for Low and High Driving Forces
Neumann, Svenja,Wenger, Oliver S.
supporting information, p. 855 - 860 (2019/01/11)
The distance dependences of electron-transfer rates (kET) in three homologous series of donor-bridge-acceptor compounds with reaction free energies (ΔGET0) of ca. -1.2, -1.6, and -2.0 eV for thermal charge recombination after initial photoinduced charge separation were studied by transient absorption spectroscopy. In the series with low driving force, the distance dependence is normal and kET decreases upon donor-acceptor distance (rDA) elongation. In the two series with higher driving forces, kET increases with increasing distance over a certain range. This counterintuitive behavior can be explained by a weakly distance-dependent electronic donor-acceptor coupling (HDA) in combination with an increasing reorganization energy (λ). Our study shows that highly exergonic electron transfers can have distance dependences that differ drastically from those of the more commonly investigated weakly exergonic reactions.
Merging Photoredox and Organometallic Catalysts in a Metal–Organic Framework Significantly Boosts Photocatalytic Activities
Zhu, Yuan-Yuan,Lan, Guangxu,Fan, Yingjie,Veroneau, Samuel S.,Song, Yang,Micheroni, Daniel,Lin, Wenbin
supporting information, p. 14090 - 14094 (2018/10/15)
Metal–organic frameworks (MOFs) have been extensively used for single-site catalysis and light harvesting, but their application in multicomponent photocatalysis is unexplored. We report here the successful incorporation of an IrIII photoredox catalyst and a NiII cross-coupling catalyst into a stable Zr12 MOF, Zr12-Ir-Ni, to efficiently catalyze C?S bond formation between various aryl iodides and thiols. The proximity of the IrIII and NiII catalytic components to each other (ca. 0.6 nm) in Zr12-Ir-Ni greatly facilitates electron and thiol radical transfers from Ir to Ni centers to reach a turnover number of 38 500, an order of magnitude higher than that of its homogeneous counterpart. This work highlights the opportunity in merging photoredox and organometallic catalysts in MOFs to effect challenging organic transformations.
