3805-10-5Relevant articles and documents
Nitrone Formation by Reaction of an Enolate with a Nitro Group
Shimizu, Hiroaki,Yoshinaga, Kohei,Yokoshima, Satoshi
, p. 2704 - 2709 (2021/04/12)
Ketones with a 2-nitrophenyl group at the α-position were treated with sodium hydroxide in methanol at 60 °C. Under these conditions, enolates derived from the ketones intramolecularly reacted with the nitro group to form a variety of nitrones. Additional experimental results, including the unexpected isolation of N-hydroxyindolinone as a byproduct, led to a proposed reaction mechanism, occurring via an α-hydroxyketone. The resultant nitrones underwent inter- and intramolecular 1,3-dipolar cycloaddition with olefins to afford polycyclic isoxazolidines.
Competition Between Cα-S and Cα-Cβ Bond Cleavage in β-Hydroxysulfoxides Cation Radicals Generated by Photoinduced Electron Transfer?
Lapi, Andrea,D'Alfonso, Claudio,Del Giacco, Tiziana,Lanzalunga, Osvaldo
, p. 1310 - 1321 (2021/06/07)
A kinetic and product study of the 3-cyano-N-methyl-quinolinium photoinduced monoelectronic oxidation of a series of β-hydroxysulfoxides has been carried out to investigate the competition between Cα-S and Cα-Cβ bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λmax ≈ 520?nm) and that of 3-CN-NMQ? (λmax ≈ 390?nm). Steady-state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo Cα-S bond cleavage, the presence of a β-hydroxy group makes, in some cases, the Cα-Cβ scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β-OH group with -OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the Cα-Cβ bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission.
Intermetallic Nanocatalyst for Highly Active Heterogeneous Hydroformylation
Chen, Minda,Gupta, Geet,Ordonez, Claudio W.,Lamkins, Andrew R.,Ward, Charles J.,Abolafia, Celia A.,Zhang, Biying,Roling, Luke T.,Huang, Wenyu
supporting information, p. 20907 - 20915 (2021/12/14)
Hydroformylation is an imperative chemical process traditionally catalyzed by homogeneous catalysts. Designing a heterogeneous catalyst with high activity and selectivity in hydroformylation is challenging but essential to allow the convenient separation and recycling of precious catalysts. Here, we report the development of an outstanding catalyst for efficient heterogeneous hydroformylation, RhZn intermetallic nanoparticles. In the hydroformylation of styrene, it shows three times higher turnover frequency (3090 h-1) compared to the benchmark homogeneous Wilkinson's catalyst (966 h-1), as well as a high chemoselectivity toward aldehyde products. RhZn is active for a variety of olefin substrates and can be recycled without a significant loss of activity. Density functional theory calculations show that the RhZn surfaces reduce the binding strength of reaction intermediates and have lower hydroformylation activation energy barriers compared to pure Rh(111), leading to more favorable reaction energetics on RhZn. The calculations also predict potential catalyst design strategies to achieve high regioselectivity.
Expeditious Total Synthesis of Hemiasterlin through a Convergent Multicomponent Strategy and Its Use in Targeted Cancer Therapeutics
Carroll, Jason S.,Charoenpattarapreeda, Jiraborrirak,Spring, David R.,Walsh, Stephen J.
supporting information, p. 23045 - 23050 (2020/11/11)
Hemiasterlin is an antimitotic marine natural product with reported sub-nanomolar potency against several cancer cell lines. Herein, we describe an expeditious total synthesis of hemiasterlin featuring a four-component Ugi reaction (Ugi-4CR) as the key st
Nitrile Synthesis by Aerobic Oxidation of Primary Amines and in situ Generated Imines from Aldehydes and Ammonium Salt with Grubbs Catalyst
Utsumi, Tatsuki,Noda, Kenta,Kawauchi, Daichi,Ueda, Hirofumi,Tokuyama, Hidetoshi
supporting information, p. 3583 - 3588 (2020/08/05)
Herein, a Grubbs-catalyzed route for the synthesis of nitriles via the aerobic oxidation of primary amines is reported. This reaction accommodates a variety of substrates, including simple primary amines, sterically hindered β,β-disubstituted amines, allylamine, benzylamines, and α-amino esters. Reaction compatibility with various functionalities is also noted, particularly with alkenes, alkynes, halogens, esters, silyl ethers, and free hydroxyl groups. The nitriles were also synthesized via the oxidation of imines generated from aldehydes and NH4OAc in situ. (Figure presented.).
Potassium Poly(Heptazine Imide): Transition Metal-Free Solid-State Triplet Sensitizer in Cascade Energy Transfer and [3+2]-cycloadditions
Antonietti, Markus,Guldi, Dirk M.,Hussain, Tanveer,Karton, Amir,Markushyna, Yevheniia,Mazzanti, Stefano,Oschatz, Martin,Sánchez Vadillo, José Manuel,Savateev, Aleksandr,Strauss, Volker,Tarakina, Nadezda V.,Tyutyunnik, Alexander P.,Walczak, Ralf,ten Brummelhuis, Katharina
supporting information, p. 15061 - 15068 (2020/06/17)
Polymeric carbon nitride materials have been used in numerous light-to-energy conversion applications ranging from photocatalysis to optoelectronics. For a new application and modelling, we first refined the crystal structure of potassium poly(heptazine imide) (K-PHI)—a benchmark carbon nitride material in photocatalysis—by means of X-ray powder diffraction and transmission electron microscopy. Using the crystal structure of K-PHI, periodic DFT calculations were performed to calculate the density-of-states (DOS) and localize intra band states (IBS). IBS were found to be responsible for the enhanced K-PHI absorption in the near IR region, to serve as electron traps, and to be useful in energy transfer reactions. Once excited with visible light, carbon nitrides, in addition to the direct recombination, can also undergo singlet–triplet intersystem crossing. We utilized the K-PHI centered triplet excited states to trigger a cascade of energy transfer reactions and, in turn, to sensitize, for example, singlet oxygen (1O2) as a starting point to synthesis up to 25 different N-rich heterocycles.
Styrene Hydroformylation with In Situ Hydrogen: Regioselectivity Control by Coupling with the Low-Temperature Water–Gas Shift Reaction
Chen, Fang,Lang, Rui,Li, Tianbo,Qiao, Botao,Su, Yang,Wang, Aiqin,Wang, Hua,Zhang, Tao
supporting information, p. 7430 - 7434 (2020/03/13)
The hydroformylation of olefins is one of the most important homogeneously catalyzed industrial reactions for aldehyde synthesis. Various ligands can be used to obtain the desired linear aldehydes in the hydroformylation of aliphatic olefins. However, in the hydroformylation of aromatic substrates, branched aldehydes are formed preferentially with common ligands. In this study, a novel approach to selectively obtain linear aldehydes in the hydroformylation of styrene and its derivatives was developed by coupling with a water–gas shift reaction on a Rh single-atom catalyst without the use of ligands. Detailed studies revealed that the hydrogen generated in situ from the water–gas shift is critical for the highly regioselective formation of linear products. The coupling of a traditional homogeneous catalytic process with a heterogeneous catalytic reaction to tune product selectivity may provide a new avenue for the heterogenization of homogenous catalytic processes.
Encapsulated liquid nano-droplets for efficient and selective biphasic hydroformylation of long-chain alkenes
Zhang, Xiaoli,Wei, Juan,Zhang, Xiaoming
supporting information, p. 14134 - 14138 (2019/09/18)
Aqueous nano-droplets of homogeneous Rh-TPPTS catalyst encapsulated within the cavity of hollow silica nanospheres were fabricated for biphasic hydroformylation of long-chain alkenes, which showed significant reaction rate enhancement effects and improved aldehyde selectivity.
Br?nsted Acid-Catalyzed Intramolecular Hydroarylation of β-Benzylstyrenes
Cai, Xiao,Keshavarz, Amir,Omaque, Justin D.,Stokes, Benjamin J.
supporting information, p. 2626 - 2629 (2017/05/24)
Using triphenylmethylium tetrakis(pentafluorophenyl)borate as a convenient Br?nsted acid precatalyst, β-(α,α-dimethylbenzyl)styrenes are shown to cyclize efficiently to afford a variety of new indanes that possess a benzylic quaternary center. The geminal dimethyl-containing quaternary center is proposed to be necessary to arm the substrate for cyclization through steric biasing.
Dual Gold Catalysis: Synthesis of Fluorene Derivatives from Diynes
Bucher, Janina,Wurm, Thomas,Taschinski, Svenja,Sachs, Eleni,Ascough, David,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
supporting information, p. 225 - 233 (2017/02/05)
1,5-Diyne systems bearing one terminal and one benzyl- or allyl-substituted alkyne attached to an aromatic backbone were converted in the presence of a gold catalyst. In a dual gold-catalyzed process, gold vinylidenes are formed that selectively undergo formal CH insertion into the C(sp2)–H bond of the offered unsaturated systems. If H atoms are present in the propargylic position, a subsequent isomerization to the aromatic system takes place leading to 9H-fluorene and 11H-benzo[b]fluorene derivatives as final products. In the case of a quaternary carbon in the propargylic position no further aromatization is observed and 10H-benzo[b]fluorene derivatives are obtained in high yield. (Figure presented.).
