14463-79-7Relevant academic research and scientific papers
Unifying Evaluation of the Technical Performances of Iron-Tetra-amido Macrocyclic Ligand Oxidation Catalysts
Denardo, Matthew A.,Mills, Matthew R.,Ryabov, Alexander D.,Collins, Terrence J.
, p. 2933 - 2936 (2016)
The main features of iron-tetra-amido macrocyclic ligand complex (a sub-branch of TAML) catalysis of peroxide oxidations are rationalized by a two-step mechanism: FeIII + H2O2 → Active catalyst (Ac) (kI), and Ac + Substrate (S) → FeIII + Product (kII). TAML activators also undergo inactivation under catalytic conditions: Ac → Inactive catalyst (ki). The recently developed relationship, ln(S0/S∞) = (kII/ki)[FeIII]tot, where S0 and S∞ are [S] at time t = 0 and ∞, respectively, gives access to ki under any conditions. Analysis of the rate constants kI, kII, and ki at the environmentally significant pH of 7 for a broad series of TAML activators has revealed a 6 orders of magnitude reactivity differential in both kII and ki and 3 orders differential in kI. Linear free energy relationships linking kII with ki and kI reveal that the reactivity toward substrates is related to the instability of the active TAML intermediates and suggest that the reactivity in all three processes derives from a common electronic origin. The reactivities of TAML activators and the horseradish peroxidase enzyme are critically compared.
Ligand Redox Noninnocence in [CoIII(TAML)]0/- Complexes Affects Nitrene Formation
De Bruin, Bas,Oudsen, Jean-Pierre H.,Rietdijk, Niels R.,Siegler, Maxime A.,Tepaske, Martijn A.,Tromp, Moniek,Van Der Vlugt, Jarl Ivar,Van Leest, Nicolaas P.,Venderbosch, Bas
supporting information, p. 552 - 563 (2020/02/20)
The redox noninnocence of the TAML scaffold in cobalt-TAML (tetra-amido macrocyclic ligand) complexes has been under debate since 2006. In this work, we demonstrate with a variety of spectroscopic measurements that the TAML backbone in the anionic complex [CoIII(TAMLred)]- is truly redox noninnocent and that one-electron oxidation affords [CoIII(TAMLsq)]. Multireference (CASSCF) calculations show that the electronic structure of [CoIII(TAMLsq)] is best described as an intermediate spin (S = 1) cobalt(III) center that is antiferromagnetically coupled to a ligand-centered radical, affording an overall doublet (S = 1/2) ground-state. Reaction of the cobalt(III)-TAML complexes with PhINNs as a nitrene precursor leads to TAML-centered oxidation and produces nitrene radical complexes without oxidation of the metal ion. The ligand redox state (TAMLred or TAMLsq) determines whether mono-or bis-nitrene radical complexes are formed. Reaction of [CoIII(TAMLsq)] or [CoIII(TAMLred)]- with PhINNs results in the formation of [CoIII(TAMLq)(Na￠Ns)] and [CoIII(TAMLq)(Na￠Ns)2]-, respectively. Herein, ligand-to-substrate single-electron transfer results in one-electron-reduced Fischer-type nitrene radicals (Na￠Ns-) that are intermediates in catalytic nitrene transfer to styrene. These nitrene radical species were characterized by EPR, XANES, and UV-vis spectroscopy, high-resolution mass spectrometry, magnetic moment measurements, and supporting CASSCF calculations.
Enantioselective Hydroxylation of Benzylic C(sp3)-H Bonds by an Artificial Iron Hydroxylase Based on the Biotin-Streptavidin Technology
Barnet, Maxime,Peterson, Ryan L.,Rebelein, Johannes G.,Rumo, Corentin,Serrano-Plana, Joan,Ward, Thomas R.
supporting information, p. 10617 - 10623 (2020/07/04)
The selective hydroxylation of C-H bonds is of great interest to the synthetic community. Both homogeneous catalysts and enzymes offer complementary means to tackle this challenge. Herein, we show that biotinylated Fe(TAML)-complexes (TAML = Tetra Amido Macrocyclic Ligand) can be used as cofactors for incorporation into streptavidin to assemble artificial hydroxylases. Chemo-genetic optimization of both cofactor and streptavidin allowed optimizing the performance of the hydroxylase. Using H2O2 as oxidant, up to ～300 turnovers for the oxidation of benzylic C-H bonds were obtained. Upgrading the ee was achieved by kinetic resolution of the resulting benzylic alcohol to afford up to >98% ee for (R)-tetralol. X-ray analysis of artificial hydroxylases highlights critical details of the second coordination sphere around the Fe(TAML) cofactor.
Oxidative Damage in Aliphatic Amino Acids and Di- and Tripeptides by the Environmental Free Radical Oxidant NO3?: the Role of the Amide Bond Revealed by Kinetic and Computational Studies
Nathanael, Joses G.,Wille, Uta
, p. 3405 - 3418 (2019/03/11)
Kinetic and computational data reveal a complex behavior of the important environmental free radical oxidant NO3? in its reactions with aliphatic amino acids and di- and tripeptides, suggesting that attack at the amide N-H bond in the peptide backbone is a highly viable pathway, which proceeds through a proton-coupled electron transfer (PCET) mechanism with a rate coefficient of about 1 × 106 M-1 s-1 in acetonitrile. Similar rate coefficients were determined for hydrogen abstraction from the α-carbon and from tertiary C-H bonds in the side chain. The obtained rate coefficients for the reaction of NO3? with aliphatic di- and tripeptides suggest that attack occurs at all of these sites in each individual amino acid residue, which makes aliphatic peptide sequences highly vulnerable to NO3?-induced oxidative damage. No evidence for amide neighboring group effects, which have previously been found to facilitate radical-induced side-chain damage in phenylalanine, was found for the reaction of NO3? with side chains in aliphatic peptides.
Redox-Active Ligand Assisted Multielectron Catalysis: A Case of CoIII Complex as Water Oxidation Catalyst
Du, Hao-Yi,Chen, Si-Cong,Su, Xiao-Jun,Jiao, Lei,Zhang, Ming-Tian
supporting information, p. 1557 - 1565 (2018/02/09)
Water oxidation is the key step in both natural and artificial photosynthesis to capture solar energy for fuel production. The design of highly efficient and stable molecular catalysts for water oxidation based on nonprecious metals is still a great challenge. In this article, the electrocatalytic oxidation of water by Na[(L4-)CoIII], where L is a substituted tetraamido macrocyclic ligand, was investigated in aqueous solution (pH 7.0). We found that Na[(L4-)CoIII] is a stable and efficient homogeneous catalyst for electrocatalytic water oxidation with 380 mV onset overpotential in 0.1 M phosphate buffer (pH 7.0). Both ligand- and metal-centered redox features are involved in the catalytic cycle. In this cycle, Na[(L4-)CoIII] was first oxidized to [(L2-)CoIIIOH] via a ligand-centered proton-coupled electron transfer process in the presence of water. After further losing an electron and a proton, the resting state, [(L2-)CoIIIOH], was converted to [(L2-)CoIV=O]. Density functional theory (DFT) calculations at the B3LYP-D3(BJ)/6-311++G(2df,2p)//B3LYP/6-31+G(d,p) level of theory confirmed the proposed catalytic cycle. According to both experimental and DFT results, phosphate-assisted water nucleophilic attack to [(L2-)CoIV=O] played a key role in O-O bond formation.
Silver-Catalyzed Efficient Synthesis of Oxindoles and Pyrroloindolines via α-Aminoalkylation of N-Arylacrylamides with Amino Acid Derivatives
Kanyiva, Kyalo Stephen,Makino, Sohei,Shibata, Takanori
supporting information, p. 496 - 499 (2018/03/06)
α-Aminoalkylation of N-arylacrylamides with amino acid derivatives was achieved by silver-catalysis in moderate to high yields. The reaction provides an efficient strategy for the synthesis of functionalized oxindoles, and is suitable for a wide range of N-arylacrylamides and amino acids, both of which are inexpensive and readily available. The oxindoles obtained were readily transformed into densely functionalized pyrroloindolines by deprotection and cyclization in one pot.
FAR SUPERIOR OXIDATION CATALYSTS BASED ON MACROCYCLIC COMPOUNDS
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Page/Page column 85, (2017/04/11)
An especially robust compound and its derivative metal complexes that are approximately one hundred-fold superior in catalytic performance to the previously invented TAML analogs is provided having the formula (I) wherein Y1, Y2, Y3 and Y4 are oxidation resistant groups which are the same or different and which form 5- or 6-membered rings with a metal, M, when bound to D; at least one Y incorporates a group that is significantly more stable towards nucleophilic attack than the organic amides of TAML activators; D is a metal complexing donor atom, preferably N; each X is a position for addition of a labile Lewis acidic substituent such as (i) H, deuterium, (ii) Li, Na, K, alkali metals, (iii) alkaline earth metals, transition metals, rare earth metals, which may be bound to one or more than one D, (iv) or is unoccupied with the resulting negative charge being balanced by a nonbonded counteraction; at least one Y may contain a site that is labile to acid dissociation, providing a mechanism for shortening complex lifetime. The new complexes deliver catalytic performances that promise to revolutionize multiple oxidation technology spaces including water purification.
Ligand-Enabled Alkynylation of C(sp3)?H Bonds with Palladium(II) Catalysts
Fu, Haiyan,Shen, Peng-Xiang,He, Jian,Zhang, Fanglin,Li, Suhua,Wang, Peng,Liu, Tao,Yu, Jin-Quan
supporting information, p. 1873 - 1876 (2017/02/05)
The palladium(II)-catalyzed β- and γ-alkynylation of amide C(sp3)?H bonds is enabled by pyridine-based ligands. This alkynylation reaction is compatible with substrates containing α-tertiary or α-quaternary carbon centers. The β-methylene C(sp
Pd-Catalyzed sequential β-C(sp3)-H arylation and intramolecular amination of δ-C(sp2)-H bonds for synthesis of quinolinones: Via an N,O-bidentate directing group
Guan, Mingyu,Pang, Yubo,Zhang, Jingyu,Zhao, Yingsheng
supporting information, p. 7043 - 7046 (2016/06/09)
The pharmacological importance of 2-quinolinone derivatives is well known. Herein, we developed an effective protocol for the synthesis of 2-quinolinone derivatives by palladium-catalyzed sequential β-C(sp3)-H arylation and selective intramolecular C(sp2)-H/N-H amination starting with aryl iodides and carboxylic acids. A novel directing group, glycine dimethylamide, was used in the synthesis. We synthesized various quinolinone derivatives, including 5-substituted quinolinones, which are difficult to obtain using the traditional pathway. The directing group could be easily removed and could be readily transformed into other useful functional groups.
Development of modifiable bidentate amino oxazoline directing group for Pd-catalyzed arylation of secondary C-H bonds
Chen, Kang,Li, Zhao-Wei,Shen, Peng-Xiang,Zhao, Hong-Wei,Shi, Zhang-Jie
supporting information, p. 7389 - 7393 (2015/05/13)
Abstract A novel bidentate α-amino oxazolinyl directing group has been developed. Different from previous directing groups, this newly designed directing group was easily prepared from amino acids and modified in structure. This auxiliary preferentially effects functionalization at secondary C(sp3)-H bonds, rather than at aryl C(sp2)-H bonds. The diastereoselectivity of direct arylation between geminal secondary C(sp3)-H bonds in linear molecules has also been realized for the first time with a chiral directing group by remote chirality relay. Two diastereoisomers are produced with the same chiral source by changing the substituents of substrates and aryl halides. A new direction: A multifunctional amino oxazoline directing group that is readily available from amino acids, has been developed, which can induce chemo-, regio- and diastereoselectivity in secondary C(sp3)-H arylation reactions. Furthermore, this directing group is removable and modifiable. Steric control and counterions play important roles in the relayed chirality transfer.
