- Unifying Evaluation of the Technical Performances of Iron-Tetra-amido Macrocyclic Ligand Oxidation Catalysts
-
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.
- Denardo, Matthew A.,Mills, Matthew R.,Ryabov, Alexander D.,Collins, Terrence J.
-
-
Read Online
- Ligand Redox Noninnocence in [CoIII(TAML)]0/- Complexes Affects Nitrene Formation
-
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.
- 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)
-
- Enantioselective Hydroxylation of Benzylic C(sp3)-H Bonds by an Artificial Iron Hydroxylase Based on the Biotin-Streptavidin Technology
-
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.
- Barnet, Maxime,Peterson, Ryan L.,Rebelein, Johannes G.,Rumo, Corentin,Serrano-Plana, Joan,Ward, Thomas R.
-
supporting information
p. 10617 - 10623
(2020/07/04)
-
- 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
-
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.
- Nathanael, Joses G.,Wille, Uta
-
p. 3405 - 3418
(2019/03/11)
-
- Redox-Active Ligand Assisted Multielectron Catalysis: A Case of CoIII Complex as Water Oxidation Catalyst
-
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.
- Du, Hao-Yi,Chen, Si-Cong,Su, Xiao-Jun,Jiao, Lei,Zhang, Ming-Tian
-
supporting information
p. 1557 - 1565
(2018/02/09)
-
- Silver-Catalyzed Efficient Synthesis of Oxindoles and Pyrroloindolines via α-Aminoalkylation of N-Arylacrylamides with Amino Acid Derivatives
-
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.
- Kanyiva, Kyalo Stephen,Makino, Sohei,Shibata, Takanori
-
supporting information
p. 496 - 499
(2018/03/06)
-
- Ligand-Enabled Alkynylation of C(sp3)?H Bonds with Palladium(II) Catalysts
-
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
- 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)
-
- FAR SUPERIOR OXIDATION CATALYSTS BASED ON MACROCYCLIC COMPOUNDS
-
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.
- -
-
Page/Page column 85
(2017/04/11)
-
- 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
-
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.
- Guan, Mingyu,Pang, Yubo,Zhang, Jingyu,Zhao, Yingsheng
-
supporting information
p. 7043 - 7046
(2016/06/09)
-
- Development of modifiable bidentate amino oxazoline directing group for Pd-catalyzed arylation of secondary C-H bonds
-
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.
- Chen, Kang,Li, Zhao-Wei,Shen, Peng-Xiang,Zhao, Hong-Wei,Shi, Zhang-Jie
-
supporting information
p. 7389 - 7393
(2015/05/13)
-
- Pd(II)-catalyzed C(sp3)-H arylation of amino acid derivatives with click-triazoles as removable directing groups
-
By using click-triazoles as conveniently approachable and removable directing groups, the direct palladium-catalyzed C(sp3)-H arylation of amino acid derivatives with various aryl iodides bearing different electronic properties has been achieved. Notably, the desired amino acid molecule can be obtained by the cleavage of the tethered click-triazoles after the catalytic reaction, which aims to provide a practical protocol for the accessibility of both natural and synthetic amino acids.
- Zhang, Guofu,Xie, Xiaoqiang,Zhu, Jianfei,Li, Shasha,Ding, Chengrong,Ding, Ping
-
supporting information
p. 5444 - 5449
(2015/05/20)
-
- Synthesis and characterization of Co(iii) amidoamine complexes: Influence of substituents of the ligand on catalytic cyclic carbonate synthesis from epoxide and carbon dioxide
-
A series of amidoamine ligands (1) and their cobalt(iii) complexes (2) were synthesized and characterized by various spectroscopic techniques including 1H-NMR and X-ray crystallographic techniques. X-ray crystallography shows that one of the complexes, 2a, forms a chiral coordination polymer due to bridge formation with Li+ associated with the complex, although the ligand is achiral. Complex 2 was employed for catalytic synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2) in a solvent free condition. A strong influence of the substituents on the ligand 1 was revealed by the varied activity of complex 2. The presence of electron withdrawing groups such as chloro (2b) and nitro (2c) increases the Lewis acidity of the catalyst, which, in turn, enhances the catalytic activity of 2. An electron withdrawing group containing complexes (2b and 2c) showed exceptionally high catalytic activity with a turnover frequency (TOF) of 662 and 602 h-1 respectively at 130°C and 300 psig CO2 pressure. On the other hand, our studies indicate that a catalyst with an electron releasing group (2d) showed relatively lower activity with a TOF of 488 h-1 under similar reaction conditions. Our results show that cobalt(iii) complexes follow the reactivity order of 2d 2a 2c 2b.
- Ramidi, Punnamchandar,Gerasimchuk, Nikolay,Gartia, Yashraj,Felton, Charlette M.,Ghosh, Anindya
-
supporting information
p. 13151 - 13160
(2013/09/12)
-
- Cyclic α-amino acids as precursors for synthesis of 2-amino-3-hetarylpyrrolin-4-ones and their spiro derivatives
-
α-Aminoisobutanoic acid and some representatives of cyclic α-amino acids were converted to corresponding 1-phthalimido- and N-trifluoroacylated acid chlorides. Treatment of 2-(1H-benzimidazol-2-yl) acetonitrile with 1-phthalimidoacid chlorides in DMF unexpectedly gave 2-(1H-benzimidazol-2-yl)-3-(dimethylamino)-2-propenenitrile. On the other hand, the reaction of hetarylacetonitriles with N-trifluoroacylated acid chlorides gave the desired (3-cyano-2-oxo-3-hetarylpropyl)-2,2,2-trifluoroacetamides that upon detrifluoroacetylation provided the target 2-amino-3-hetarylpyrrolin-4- ones. The acylation of benzoimidazolylamino-pyrrolinones by benzoyl chloride leads to formation of 3-benzoyl-2,3-dihydro-5-phenyl-1H-benzo[4,5]imidazo[1,2-c] pyrrolo[3,2-e]pyrimidin-1-ones. Springer-Verlag 2012.
- Dobrydnev, Alexey V.,Volovnenko, Tatyana A.,Volovenko, Yulian M.,Palamarchuk, Gennady V.,Shishkin, Oleg V.
-
experimental part
p. 779 - 789
(2012/09/22)
-
- Synthesis of new cyclic imides derivatives with potential hypolipidemic activity
-
Certain new nitrogen-substituted derivatives of cyclic imides phthalimide (a), 1,8-naphthalimide (b), and diphenimide (c), were synthesized aiming to obtain potent hypolipidemic agents. Thus, 2-(N-imido) propanoic acids, 2-(N-phthalimido)-2-methylpropionic acid, and their ethyl esters were synthesized (Target derivative A). Also their corresponding N-substituted-2-(N- imido) propionamides and 2-(N-phthalimido)-2-methylpropionamides were prepared (Target derivative B). In addition, N-phthalimidomethyleneoxy acetate was prepared. Some of the newly prepared compounds were subjected to 3D studies and were found to be superimposed on Clofibrate, which is the first generation of fibrate drugs. The preliminary evaluation of hypolipidemic activity of the newly prepared compounds against triton WR-1339-induced hyperlipidemia in rat showed that several derivatives have demonstrated significant lowering of serum total cholesterol and triglyceride levels at dose of 150 mg/kg/i.p. comparing with Fenofibrate which is one of the second generations of fibrate drugs. Springer Science+Business Media, LLC 2010.
- El-Zahabi, Mohamed A.,Gad, Laila M.,Bamanie, Faida H.,Al-Marzooki, Zohair
-
experimental part
p. 75 - 84
(2012/06/01)
-
- CATALYTICS ASYMMETRIC ACTIVATION OF UNACTIVATED C-H BONDS, AND COMPOUNDS RELATED THERETO
-
One aspect of the present invention is directed in part to catalytic and stereoselective functionalization of unactivated C-H bonds of simple organic substrates. The compounds and methods provided herein allow one to control the stereochemistry in a C-H activation step, activate substrates containing α-hydrogens next to the directing group, and remove a directing group under mild conditions. One aspect of the present invention relates to a transition-metal-catalyzed method for selective and asymmetric oxidation of carbons located in a β- or γ-position relative to an auxiliary. Another aspect of the invention relates to the enantiomerically-enriched substrates and the enantiomerically-enriched products formed via said method. In certain embodiments, oxazoline and oxazinone directing groups are used. In addition, the Boc protecting group has been identified as a directing group which does not necessitate removal.
- -
-
Page/Page column 89-90
(2010/10/20)
-
- Enantioselective and diastereoselective synthesis of fluorinated dipeptides by late electrophilic fluorination
-
A series of optically enriched monofluorinated dipeptides incorporating an α-fluoro-α-amino acid were prepared by enantio- and diastereoselective electrophilic fluorination. This previously unsuccessful approach to fluorinated dipeptides can now be achieved with up to 73:27 enantiomeric ratio and high >98:2 diastereomeric ratio.
- Mohar, Barbara,Sterk, Damjan,Ferron, Laurent,Cahard, Dominique
-
p. 5029 - 5031
(2007/10/03)
-
- Synthesis of macrocyclic tetraamido compounds and new metal insertion process
-
An improved method of synthesizing a macrocyclic tetraamido compound includes protecting the amino portion of an amino carboxylic acid to form a protected amino carboxylic acid; exposing the protected amino carboxylic acid to a first solvent, preferably a hydrocarbon solvent, such as toluene or 1,2-dichloroethane, dichloromethane, dibromomethane and 1,2-dibromoethane. The carboxylic acid portion of the protected amino carboxylic acid is then converted to an activated carboxylic acid by one of esterification or acid halide formation, to form a protected amino activated carboxylic acid derivative. The protected amino activated carboxylic acid derivative is reacted with a diamine in the presence of a second solvent, such as THF or ,2-dichloroethane, dichloromethane, dibromomethane and 1,2-dibromoethane, to form a protected diamide diamine intermediate. Following deprotection, the diamide diamine intermediate is reacted with an activated diacid, such as an activated malonate, oxalate or succinate derivative to form the macrocyclic tetraamido compound. The macrocyclic tetraamido compound may further be complexed with a transition metal.
- -
-
-
- Macrocyclic tetraamido ligands as bleaching catalysts and synthesis thereof
-
The invention relates to a novel synthetic route for a group of ligands and to an improved catalyst containing the ligand. It provides a method for the synthesis of a ligand having the structure: (I) The invention also provides use of a ligand for inhibiting dye transfer.
- -
-
-
- Methyl 2-((succinimidooxy)carbonyl)benzoate (MSB): a new, efficient reagent for N-phthaloylation of amino acid and peptide derivatives.
-
A new, efficient, and readily available reagent, methyl 2-((succinimidooxy)carbonyl)benzoate (MSB), for N-phthaloylation of amino acids and amino acid derivatives is described. The phthaloylation procedure is simple and racemization-free and gives excellent results with alpha-amino acids, alpha-amino alcohols, dipeptides, alpha-amino carboxamides, and alpha-amino esters.
- Casimir, J Richard,Guichard, Gilles,Briand, Jean-Paul
-
p. 3764 - 3768
(2007/10/03)
-
- Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 7. Cyclisation of amino acid derived α-phthalimidoacyl ylides to give pyrroloisoindolediones
-
A series of 11 amino acid-derived stabilised ylides 12-14 and 16 have been prepared and characterised. In one case, for compound 17, an X-ray structure determination supports formulation of the compounds as phosphonium enolates. Flash vacuum pyrolysis (FVP) of 12 and 13 at 500°C results in loss of R23PO between the ylide function and one carbonyl of the phthalimido group to give products characterised spectroscopically as the pyrroloisoindolediones 18. The identity of these is also supported by the results of 13C and 15N labelling experiments, but owing to their high reactivity complete separation from the phosphine oxide was not generally possible even when Bu3PO rather than Ph3PO was involved. Chromatographic purification of 29, similarly produced by FVP of 14, led to partial hydrolysis, rearrangement and decarboxylation to give 30. FVP of 12 at 750°C gave the 1-unsubstituted pyrroloisoindolediones 19 in two cases.
- Aitken, R. Alan,Cooper, Harris R.,Mehrotra, Amit P.
-
p. 475 - 483
(2007/10/03)
-
- Specific Inhibitors in Vitamin Biosynthesis. Part 7. Syntheses of Blocked 7,8-Dihydropteridines via &α-Amino Ketones
-
The synthesis of 15 blocked 7,8-dihydropteridines is described in which the pyrazine ring is built from a derivative of an α-amino ketone.Three routes to the amino ketones based upon amino acids, nitrosyl chloride addition to alkenes, and nitro alcohols are discussed.The compounds synthesised are inhibitors of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase , an enzyme in the pathway leading to dihydrofolate, and the inhibitory potencies of the compounds are discussed in the light of a hypothetical active site model for the enzyme.
- Al-Hassan, Saiba S.,Cameron, Robert J.,Curran, Adrian W. C.,Lyall, William J. S.,Nicholson, Sydney H.,et al.
-
p. 1645 - 1660
(2007/10/02)
-