1778-08-1Relevant academic research and scientific papers
Aryl Carbamates: Mechanisms of Orthosodiations and Snieckus-Fries Rearrangements
Ma, Yun,Woltornist, Ryan A.,Algera, Russell F.,Collum, David B.
, p. 9051 - 9057 (2019)
Aryl carbamates are orthometalated by sodium diisopropylamide (NaDA) in tetrahydrofuran. The resulting arylsodiums undergo Snieckus-Fries rearrangement to give orthoacylated phenols in good yield. The intermediate arylsodiums and resulting orthoacylated phenolates are suggested to be monomeric. The rate-limiting step in the two-step sequence depends on the steric demands of the carbamoyl moiety and the substituents in the meta position of the arene. Rate studies reveal a dominant disolvated-monomer-based orthometalation followed by a di- or trisolvated arylsodium monomer-based rearrangement. Kinetic evidence of a NaDA-catalyzed Snieckus-Fries rearrangement suggests the intermediacy of mixed trimers. Competitive halide eliminations to form benzyne are also discussed.
A series of NiII-flavonolate complexes as structural and functional ES (enzyme-substrate) models of the NiII-containing quercetin 2,3-dioxygenase
Sun, Ying-Ji,Huang, Qian-Qian,Zhang, Jian-Jun
, p. 6480 - 6489 (2014)
NiII-flavonolate complexes [NiIILR(fla)] (LRH: 2-{[bis(pyridin-2-ylmethyl)amino]methyl}-p/m-R-benzoic acid, R: p-OMe (1), p-Me (2), m-Br (4) and m-NO2 (5), fla: flavonolate) were synthesized and characterized with relevance to structural and functional models for the ES (enzyme-substrate) adduct of the NiII-containing quercetin 2,3-dioxygenase (2,3-QD). Their structures, spectroscopic features, redox properties and the reactivity toward molecular oxygen have been investigated. The complexes show a similar distorted octahedral structure and higher enzyme-type dioxygenation reactivity than other reported metal-flavonolate complexes in the oxidative O-heterocyclic ring-opening of the bound substrate flavonolate at lower temperature owing to the introduced carboxylate group in the supporting model ligands. The reaction rate shows first-order dependence on both of the complex and O2 and the second-order rate constant k fits a Hammett linear free energy relationship (ρ = -0.71) for the substituent group in the supporting model ligand L R. The complexes exhibit substituent group dependent structures, properties and reactivity and there are some relationship among them, which could be ascribed to the electronic nature of the substituent group via the benzoate, NiII ion and O(4)C(27)-C(21)C(22) electron conduit . In a word, the stronger electron donating group could induce a smaller torsion angle, larger λmax and lower redox potential of the bound flavonolate, making a higher reactivity finally. This study is the first example of a series of structural and functional ES models of the Ni II-containing 2,3-QD, providing important insights into the structure-property-reactivity relationship, the electronic substituent effects and carboxylate effects on the enzymatic reactivity and the catalytic role of the NiII-containing 2,3-QD. This journal is the Partner Organisations 2014.
Flavonolate complexes of MII (M = Mn, Fe, Co, Ni, Cu, and Zn). structural and functional models for the ES (Enzyme-substrate) complex of quercetin 2,3-dioxygenase
Sun, Ying-Ji,Huang, Qian-Qian,Tano, Tetsuro,Itoh, Shinobu
, p. 10936 - 10948 (2013)
A series of flavonolate complexes [MIIL(fla)] (M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5), and Zn (6), LH: 2-{[bis(pyridin-2-ylmethyl)amino] methyl}benzoic acid, fla: flavonolate) have been synthesized as structural and functional models for the ES (enzyme-substrate) complexes of the active site of various MII-containing quercetin 2,3-dioxygenase (2,3-QD) and their structures, spectroscopic features, and redox properties, as well as the reactivity toward molecular oxygen, have been investigated. The metal centers of [FeIIL(fla)]·H2O (2), [CoIIL(fla)] ·CH3OH (3), and [NiIIL(fla)] (4) exhibit a distorted octahedral geometry with two oxygen atoms of fla, one oxygen atom of the benzoate group of ligand L, and three nitrogen atoms of ligand L, in which oxygen atom of the carbonyl group of fla and one of the pyridine nitrogen atoms occupy the axial positions. The complexes [MIIL(fla)] exhibit relatively high reactivity in the oxidative ring-opening of the bound flavonolate at lower temperature, presumably due to the existing carboxylate group in the supporting ligand. Thus, our complexes act as good functional ES models of various metal(II)-containing 2,3-QD. In addition, complexes [Fe IIL(fla)]·H2O (2), [CoIIL(fla)] ·CH3OH (3), and [NiIIL(fla)] (4) are the first structurally characterized FeII-, CoII-, and Ni II-flavonolate complexes, as an active site ES model of Fe II-, CoII-, and NiII-containing 2,3-QD, respectively. The model complexes exhibit notably different reactivity in the order of Fe (2) > Cu (5) > Co (3) > Ni (4) > Zn (6) > Mn (1). The differences in the reactivity among them may be attributed to the redox potential of the coordinated flavonolate of the complexes, which are remarkably influenced by the Lewis acidity of the metal ion and its coordination environment. Our study is the first example of the metal ion effects on the enzyme-like dioxygenation reactivity, providing important insights into the metal ion effects on the enzymatic reactivity of various metal(II)-containing 2,3-QD.
Catalytic dioxygenation of flavonol by MII-complexes (M = Mn, Fe, Co, Ni, Cu and Zn)-mimicking the MII-substituted quercetin 2,3-dioxygenase
Sun, Ying-Ji,Huang, Qian-Qian,Li, Pei,Zhang, Jian-Jun
, p. 13926 - 13938 (2015)
In order to get insights into the metal ion effects and the carboxylate effects on enzymatic activity, a series of the carboxylate ligand supported transition metal complexes [MIIL(OAc)] (M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5) and Zn (6); L
Suppressing the anionic fries rearrangement of aryl dialkylcarbamates; the isolation of a crystalline ortho-deprotonated carbamate
Garcia, Felipe,McPartlin, Mary,Morey, James V.,Nobuto, Daisuke,Kondo, Yoshinori,Naka, Hiroshi,Uchiyama, Masanobu,Wheatley, Andrew E. H.
, p. 644 - 647 (2008)
In the presence of organolithium bases phenyl dialkylcarbamates have previously been shown to undergo facile rearrangement to yield the corresponding salicylamides. However, heterometallic lithium diethyl(2,2,6,6- tetramethylpiperidido)zincate achieves th
Oxygenolysis of a series of copper(ii)-flavonolate adducts varying the electronic factors on supporting ligands as a mimic of quercetin 2,4-dioxygenase-like activity
Anoop, Anakuthil,Dey, Subhasis,Mandal, Sukanta,Podder, Nirmalya
supporting information, p. 4338 - 4353 (2022/04/07)
Four copper(ii)-flavonolate compounds of type [Cu(LR)(fla)] {where LR = 2-(p-R-benzyl(dipyridin-2-ylmethyl)amino)acetate; R = -OMe (1), -H (2), -Cl (3) and -NO2 (4)} have been developed as a structural and functional enzyme-substrate (ES) model of the Cu2+-containing quercetin 2,4-dioxygenase enzyme. The ES model complexes 1-4 are synthesized by reacting 3-hydroxyflavone in the presence of a base with the respective acetate-bound copper(ii) complexes, [Cu(LR)(OAc)]. In the presence of dioxygen the ES model complexes undergo enzyme-type oxygenolysis of flavonolate (dioxygenase type bond cleavage reaction) at 80 °C in DMF. The reactivity shows a substituent group dependent order as -OMe (1) > -H (2) > -Cl (3) > ?NO2 (4). Experimental and theoretical studies suggest a single-electron transfer (SET) from flavonolate to dioxygen, rather than valence tautomerism {[CuII(fla?)] ? [CuI(fla˙)]}, to generate the reactive flavonoxy radical (fla˙) that reacts further with the superoxide radical to bring about the oxygenative ring opening reaction. The SET pathway has been further verified by studying the dioxygenation reaction with a redox-inactive Zn2+ complex, [Zn(LOMe)(fla)] (5).
Rhoda-Electrocatalyzed Bimetallic C?H Oxygenation by Weak O-Coordination
Tan, Xuefeng,Massignan, Leonardo,Hou, Xiaoyan,Frey, Johanna,Oliveira, Jo?o C. A.,Hussain, Masoom Nasiha,Ackermann, Lutz
, p. 13264 - 13270 (2021/05/06)
Rhodium-electrocatalyzed arene C?H oxygenation by weakly O-coordinating amides and ketones have been established by bimetallic electrocatalysis. Likewise, diverse dihydrooxazinones were selectively accessed by the judicious choice of current, enabling twofold C?H functionalization. Detailed mechanistic studies by experiment, mass spectroscopy and cyclovoltammetric analysis provided support for an unprecedented electrooxidation-induced C?H activation by a bimetallic rhodium catalysis manifold.
Intramolecular interception of the Newman-Kwart rearrangement by carboxylic acids
Ablott, Timothy A.,Fishburn, Mitchell G.,Turner, David R.,Richardson, Christopher
supporting information, (2020/07/03)
Instead of undergoing the Newman-Kwart rearrangement, thermally-promoted reactions of O-aryl dimethylthiocarbamates featuring ortho-carboxylic acid substituents result in the loss of carbonylsulfide and formation of N,N-dimethylsalicylamides in high yield
C?H Oxygenation Reactions Enabled by Dual Catalysis with Electrogenerated Hypervalent Iodine Species and Ruthenium Complexes
Massignan, Leonardo,Tan, Xuefeng,Meyer, Tjark H.,Kuniyil, Rositha,Messinis, Antonis M.,Ackermann, Lutz
supporting information, p. 3184 - 3189 (2020/01/24)
The catalytic generation of hypervalent iodine(III) reagents by anodic electrooxidation was orchestrated towards an unprecedented electrocatalytic C?H oxygenation of weakly coordinating aromatic amides and ketones. Thus, catalytic quantities of iodoarenes in concert with catalytic amounts of ruthenium(II) complexes set the stage for versatile C?H activations with ample scope and high functional group tolerance. Detailed mechanistic studies by experiment and computation substantiate the role of the iodoarene as the electrochemically relevant species towards C?H oxygenations with electricity as a sustainable oxidant and molecular hydrogen as the sole by-product. para-Selective C?H oxygenations likewise proved viable in the absence of directing groups.
Selective cleaving the N–P bond of difluoromethylene phosphabetaines for effective synthesis of β-ketoamides
Liu, Yingle,Yang, Tao,Dong, Yuting,Cai, Junjie,Luo, Gen,Tong, Xia,Jiang, Yan,Yang, Yi,Xu, Xiu-Hua
supporting information, p. 1934 - 1937 (2019/06/25)
An unprecedent transition-metal-free protocol for the synthesis of β-ketoamides from β-ketoesters is described. This method involves selective cleaving N–P bond of an unusual aminating reagent, [tris(dimethylamino)phosphonio]difluoroacetate (ADFA), which
