1440419-03-3Relevant articles and documents
Electrophile, Substrate Functionality, and Catalyst Effects in the Synthesis of α-Mono and Di-Substituted Benzylamines via Visible-Light Photoredox Catalysis in Flow
Vilé, Gianvito,Richard-Bildstein, Sylvia,Lhuillery, Arnaud,Rueedi, Georg
, p. 3786 - 3794 (2018)
We report herein the facile and one-pot synthesis of α-mono- and di-substituted benzylamines from cheap and readily available α-amino acids, via photocatalytic decarboxylative arylation in flow. This enables to access intermediates and building blocks that are difficult to obtain via other synthetic routes, but are key for the manufacture of pharmaceuticals, agrochemicals, and fine chemicals. The optimal decarboxylative conditions were identified through a high-throughput evaluation of catalysts, organic or inorganic bases, ligands, and reaction parameters (i. e., contact time, temperatures, and photoelectron power). The reaction turned out to be electronically controlled as the yields increased with increasing electron-density on the aryl moiety. The results were correlated with the redox properties of the photocatalysts, deriving catalyst structure-performance relationships which can facilitate the future identification of even better materials. In addition, compared to traditional batch chemistry, the use of a flow protocol led to quicker reactions (30 min instead of 12–72 h) and ensured more predictable reaction scale-ups.
Selective Coupling of 1,2-Bis-Boronic Esters at the more Substituted Site through Visible-Light Activation of Electron Donor–Acceptor Complexes
Aggarwal, Varinder K.,Noble, Adam,Wang, Hui,Wu, Jingjing
, (2022/03/14)
1,2-Bis-boronic esters are useful synthetic intermediates particularly as the two boronic esters can be selectively functionalized. Usually, the less hindered primary boronic ester reacts, but herein, we report a coupling reaction that enables the reversal of this selectivity. This is achieved through the formation of a boronate complex with an electron-rich aryllithium which, in the presence of an electron-deficient aryl nitrile, leads to the formation of an electron donor–acceptor complex. Following visible-light photoinduced electron transfer, a primary radical is generated which isomerizes to the more stable secondary radical before radical-radical coupling with the arene radical-anion, giving β-aryl primary boronic ester products. The reactions proceed under catalyst-free conditions. This method also allows stereodivergent coupling of cyclic cis-1,2-bis-boronic esters to provide trans-substituted products, complementing the selectivity observed in the Suzuki–Miyaura reaction.
Photoactive electron donor-acceptor complex platform for Ni-mediated C(sp3)-C(sp2) bond formation
Kammer, Lisa Marie,Badir, Shorouk O.,Hu, Ren-Ming,Molander, Gary A.
, p. 5450 - 5457 (2021/05/05)
A dual photochemical/nickel-mediated decarboxylative strategy for the assembly of C(sp3)-C(sp2) linkages is disclosed. Under light irradiation at 390 nm, commercially available and inexpensive Hantzsch ester (HE) functions as a potent organic photoreductant to deliver catalytically active Ni(0) species through single-electron transfer (SET) manifolds. As part of its dual role, the Hantzsch ester effects a decarboxylative-based radical generation through electron donor-acceptor (EDA) complex activation. This homogeneous, net-reductive platform bypasses the need for exogenous photocatalysts, stoichiometric metal reductants, and additives. Under this cross-electrophile paradigm, the coupling of diverse C(sp3)-centered radical architectures (including primary, secondary, stabilized benzylic, α-oxy, and α-amino systems) with (hetero)aryl bromides has been accomplished. The protocol proceeds under mild reaction conditions in the presence of sensitive functional groups and pharmaceutically relevant cores.
Photoredox Heterobimetallic Dual Catalysis Using Engineered Covalent Organic Frameworks
Alemán, José,Imaz, Inhar,López-Magano, Alberto,Mas-Ballesté, Rubén,Maspoch, Daniel,Ortín-Rubio, Borja
, p. 12344 - 12354 (2021/10/12)
The functionalization of an imine-based layered covalent organic framework (COF), containing phenanthroline units as ligands, has allowed the obtention of a heterobimetallated material. Photoactive Ir and Ni fragments were immobilized within the porous structure of the COF, enabling heterogeneous light-mediated Csp3-Csp2cross-couplings. As radical precursors, potassium benzyl- and alkoxy-trifluoroborates, organic silicates, and proline derivatives were employed, which brings out the good versatility ofIr,Ni@Phen-COF. Moreover, in all the studied cases, an enhanced activity and stability have been observed in comparison with analogous homogenous systems.
O-benzoylhydroxylamines as alkyl nitrene precursors: Synthesis of saturated N-heterocycles from primary amines
Noda, Hidetoshi,Asada, Yasuko,Shibasaki, Masakatsu
, p. 8769 - 8773 (2020/10/12)
We introduce O-benzoylhydroxylamines as competent alkyl nitrene precursors. The combination of readily available, stable substrates and a proficient rhodium catalyst provides a straightforward means for the construction of various pyrrolidine rings from the corresponding primary amines. Preliminary mechanistic investigation suggests that the structure of the nitrene precursor plays a role in determining the nature of the resulting reactive intermediate.
Benzaldehyde- And Nickel-Catalyzed Photoredox C(sp3)-H Alkylation/Arylation with Amides and Thioethers
Si, Xiaojia,Zhang, Lumin,Hashmi, A. Stephen K.
supporting information, p. 6329 - 6332 (2019/08/20)
Herein a synergistic combination of a nickel catalyst and benzaldehyde for the utilization of amides and thioethers in C(sp3)-H alkylation and arylation reactions employing simple aryl or alkyl halides is reported. This method provides a simple and cheap strategy for the direct functionalization of amides and thioethers. Readily available starting materials, mild reaction conditions, a good functional-group tolerance, and a broad substrate scope make this methodology attractive and practical for pharmaceutical and synthetic chemistry.
3-amino-fluorene-2,4-dicarbonitriles (AFDCs) as photocatalysts for the decarboxylative arylation of α-amino acids and α-oxy acids with arylnitriles
Chen, Yiyang,Lu, Ping,Wang, Yanguang
supporting information, p. 2130 - 2133 (2019/03/26)
1-(4-(9H-Carbazol-9-yl)phenyl)-3-amino-9H-fluorene-2,4-dicarbonitrile as a new photocatalyst for the decarboxylative cross-coupling reaction of α-amino acids or α-oxy carboxylic acids with arylnitriles is described. This light-driven reaction enables a va
RETRACTED ARTICLE: Heterogeneous Titania-Photoredox/Nickel Dual Catalysis: Decarboxylative Cross-Coupling of Carboxylic Acids with Aryl Iodides
McTiernan, Christopher D.,Leblanc, Xavier,Scaiano, Juan C.
, p. 2171 - 2175 (2017/08/09)
The efficient, mild, and semiheterogeneous decarboxylative cross-coupling of a variety alkyl carboxylic acids with aryl iodides has been accomplished through a merger of TiO2 photoredox and nickel cross-coupling chemistries. The protocol is tolerant to a wide range of substituted aryl iodides and alkyl carboxylic acids. Through replacement of the commonly employed Ir transition-metal complexes with P25 TiO2 as photocatalyst, we show that these transformations can be heterogenized with little effect on the efficiency of these transformations, while at the same time decreasing the associated costs due to the reusability and inexpensive nature of the TiO2 photocatalyst.
Donor-Acceptor Fluorophores for Visible-Light-Promoted Organic Synthesis: Photoredox/Ni Dual Catalytic C(sp3)-C(sp2) Cross-Coupling
Luo, Jian,Zhang, Jian
, p. 873 - 877 (2016/02/18)
We describe carbazolyl dicyanobenzene (CDCB)-based donor-acceptor (D-A) fluorophores as a class of cheap, easily accessible, and efficient metal-free photoredox catalysts for organic synthesis. By changing the number and position of carbazolyl and cyano groups on the center benzene ring, CDCBs with a wide range of photoredox potentials are obtained to effectively drive the energetically demanding C(sp3)-C(sp2) cross-coupling of carboxylic acids and alkyltrifluoroborates with aryl halides via a photoredox/Ni dual catalysis mechanism. This work validates the utility of D-A fluorophores in guiding the rational design of metal-free photoredox catalysts for visible-light-promoted organic synthesis.
Effects of Molecular Oxygen, Solvent, and Light on Iridium-Photoredox/Nickel Dual-Catalyzed Cross-Coupling Reactions
Oderinde, Martins S.,Varela-Alvarez, Adrian,Aquila, Brian,Robbins, Daniel W.,Johannes, Jeffrey W.
, p. 7642 - 7651 (2015/08/18)
In order to achieve reproducibility during iridium-photoredox and nickel dual-catalyzed sp3-sp2 carbon-carbon bond-forming reactions, we investigated the role that molecular oxygen (O2), solvent and light-source (CF lamp o
