- A dianionic C3-symmetric scorpionate: Synthesis and coordination chemistry
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Introducing charges into ligand systems fine-tunes their electronic properties and influences the solubility of their metal complexes. Herein, we present a synthesis of a dianionic, C3-symmetric ligand combining three anionic N-donors tethered to a positively charged phosphonium center. The tris-skatylmethylphosphonium (TSMP) ligand, isolated in the form of its dipotassium salt TSMPK2, is the first dianionic homoscorpionate capable of metal exchange. The potassium cations in TSMPK2 are exchangeable for other metals, which results in rich coordination chemistry. Thus, the ligand displays a bridging μ2:κ2:κ1 coordination mode with trigonal planar Cu(i) centers in the tetrameric complex [(TSMP)Cu]44-. The κ3 mode is accessed upon addition of 1 equiv. of P(OEt)3 per Cu(i) to yield the tetrahedral monomeric complex [(TSMP)CuP(OEt)3]-. Both Fe(ii) and Ni(ii) in pyridine give octahedral high-spin κ3 complexes with composition (TSMP)M(Py)3 (M = Fe, Ni). Displacement of three pyridine ligands in (TSMP)Fe(Py)3 for a second equivalent of TSMP gives a high-spin pseudotetrahedral 2?:?1 complex [(TSMP)2Fe]2- with the ligands in κ2 coordination mode. The reduction in coordination number is likely due to electrostatic repulsion of the negatively-charged indolides as well as their weaker π-accepting character as compared to pyridine. This journal is
- Tretiakov, Serhii,Damen, Johannes A. M.,Lutz, Martin,Moret, Marc-Etienne
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- An entry to 2-(cyclobut-1-en-1-yl)-1: H -indoles through a cyclobutenylation/deprotection cascade
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A transition-metal-free strategy for the synthesis of 2-(cyclobut-1-en-1-yl)-1H-indoles under mild conditions is described herein. A series of substituted 2-(cyclobut-1-en-1-yl)-1H-indoles are accessed by a one-pot cyclobutenylation/deprotection cascade from N-Boc protected indoles. Preliminary experimental and density functional theory calculations suggest that a Boc-group transfer is involved in the underlying mechanism.
- Natho, Philipp,Yang, Zeyu,Allen, Lewis A. T.,Rey, Juliette,White, Andrew J. P.,Parsons, Philip J.
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supporting information
p. 4048 - 4053
(2021/05/19)
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- Stereoselective Synthesis of Cyclohepta[b]indoles by Visible-Light-Induced [2+2]-Cycloaddition/retro-Mannich-type Reactions
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A novel method for the concise synthesis of cyclohepta[b]indoles in high yields was developed. The method involves a visible-light-induced, photocatalyzed [2+2]-cycloaddition/ retro-Mannich-type reaction of enaminones. Experimental and computational studies suggested that the reaction is a photoredox process initiated by single-electron oxidation of an enaminone moiety, which undergoes subsequent cyclobutane formation and rapidly fragmentation in a radical-cation state to form cyclohepta[b]indoles.
- Mu, Xin-Peng,Li, Yuan-He,Zheng, Nan,Long, Jian-Yu,Chen, Si-Jia,Liu, Bing-Yan,Zhao, Chun-Bo,Yang, Zhen
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supporting information
p. 11211 - 11216
(2021/04/09)
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- Tridentate Nickel(II)-Catalyzed Chemodivergent C-H Functionalization and Cyclopropanation: Regioselective and Diastereoselective Access to Substituted Aromatic Heterocycles
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A Schiff-base nickel(II)-phosphene-catalyzed chemodivergent C-H functionalization and cyclopropanation of aromatic heterocycles is reported in moderate to excellent yields and very good regioselectivity and diastereoselectivity. The weak, noncovalent interaction between the phosphene ligand and Ni center facilitates the ligand dissociation, generating the electronically and coordinatively unsaturated active catalyst. The proposed mechanisms for the reported reactions are in good accord with the experimental results and theoretical calculations, providing a suitable model of stereocontrol for the cyclopropanation reaction.
- Nag, Ekta,Gorantla, Sai Manoj N. V. T.,Arumugam, Selvakumar,Kulkarni, Aditya,Mondal, Kartik Chandra,Roy, Sudipta
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supporting information
p. 6313 - 6318
(2020/09/02)
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- Metal-Free Oxidative Cross Coupling of Indoles with Electron-Rich (Hetero)arenes
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A new method for the synthesis of bi-heteroaryls is reported, based on the umpolung of indoles with benziodoxol(on)e hypervalent iodine reagents (IndoleBX). The oxidative coupling of IndoleBX with an equimolar amount of electron-rich benzenes, indoles, pyrroles, and thiophenes proceeded under mild transition-metal-free conditions. Functionalized non-symmetrical bi-indolyl heterocycles were accessed efficiently. Introduction of a new type of C2-substituted indole benziodoxole reagents further allowed extending the scope of the reaction to NH unprotected and C3-alkylated indoles. The obtained bi-heterocycles are important building blocks in synthetic and medicinal chemistry, and could be easily transformed into more complex heterocyclic systems.
- Caramenti, Paola,Nandi, Raj Kumar,Waser, Jerome
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supporting information
p. 10049 - 10053
(2018/07/29)
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- Strongly Reducing, Visible-Light Organic Photoredox Catalysts as Sustainable Alternatives to Precious Metals
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Photoredox catalysis is a versatile approach for the construction of challenging covalent bonds under mild reaction conditions, commonly using photoredox catalysts (PCs) derived from precious metals. As such, there is need to develop organic analogues as sustainable replacements. Although several organic PCs have been introduced, there remains a lack of strongly reducing, visible-light organic PCs. Herein, we establish the critical photophysical and electrochemical characteristics of both a dihydrophenazine and a phenoxazine system that enables their success as strongly reducing, visible-light PCs for trifluoromethylation reactions and dual photoredox/nickel-catalyzed C?N and C?S cross-coupling reactions, both of which have been historically exclusive to precious metal PCs.
- Du, Ya,Pearson, Ryan M.,Lim, Chern-Hooi,Sartor, Steven M.,Ryan, Matthew D.,Yang, Haishen,Damrauer, Niels H.,Miyake, Garret M.
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supporting information
p. 10962 - 10968
(2017/08/22)
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- Microwave-assisted synthesis of 3,1-benzoxazin-2-ones from 3-hydroxyoxindoles
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A general protocol for the synthesis of 3,1-benzoxazin-2-ones 18 from 3-hydroxyoxindoles 16 in a two steps sequence through phenylsuccinates or phenylpropionates 17 is described. Best reaction conditions for ring opening of 16 to succinates or propionates 17 were achieved using alcohol/silica gel, while cyclization of 17 to benzoxazinones 18 was easily done with HCl/alcohol. It was also found that 17 and 18 can be transesterified using HCl/alcohol. Most transformations were carried out by traditional heating and by microwave (MW) irradiation to accelerate reaction rates.
- Suarez-Castillo, Oscar R.,Bautista-Hernandez, Claudia I.,Sanchez-Zavala, Maricruz,Melendez-Rodriguez, Myriam,Sierra-Zenteno, Araceli,Morales-Rios, Martha S.,Joseph-Nathan, Pedro
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p. 2147 - 2171,25
(2020/08/31)
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- A trans diacyloxylation of indoles
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A trans diacyloxylation of indoles is accomplished by employing PhI(OAc)2 as the oxidant. A broad range of functional groups are well tolerated. Both the electronic properties of the N-protecting groups of indoles and the acidity of the reaction media play important roles in the selectivity of indole acyloxylation reactions. The Royal Society of Chemistry 2012.
- Liu, Qiang,Zhao, Qing Yong,Liu, Jie,Wu, Pan,Yi, Hong,Lei, Aiwen
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supporting information; experimental part
p. 3239 - 3241
(2012/04/10)
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- Enantioselective cyclopropanation of indoles: Construction of all-carbon quaternary stereocenters
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The first enantioselective copper-catalyzed cyclopropanation of N-acyl indoles is described. Using carbohydrate-based bis(oxazoline) ligands (glucoBox), the products were obtained in up to 72% ee. Cyclopropanation of N-Boc 3-methyl indole yielded a product with an all-carbon quaternary stereocenter, which is a valuable building block for the synthesis of indole alkaloids: Deprotection and rearrangement gave a tricyclic hemiaminal ester in 96% ee, which was subsequently employed as a key intermediate for the synthesis of (-)-desoxyeseroline.
- ?züduru, Gülsüm,Schubach, Thea,Boysen, Mike M. K.
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supporting information
p. 4990 - 4993
(2013/01/15)
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- Reduction of 1-pyrrolyl and 1-indolyl carbamates to hemiaminals
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Hemiaminals of pyrroles and indoles have been prepared from the lithium aluminum hydride reduction of 1-pyrrolyl and 1-indolyl carbamates with good yields (67-82%). These carbamates are more reactive than aliphatic amides and carbamates under the LAH reduction, but less reactive than esters.
- Hsu, He-Chu,Hou, Duen-Ren
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supporting information; experimental part
p. 7169 - 7171
(2010/03/03)
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- Double functionalization of N-Boc-3-(tosylmethyr)indole exploiting the activating properties of the tosyl group
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The anion prepared from N-Boc-3-(tosylmethyl)indole using NaH in DMF can be readily functionalized by reaction with various electrophiles. The obtained sulfonyl indoles, upon removal of the N-protecting group, undergo nucleophilic attack via a vinylogous imino derivative, leading to branched 3-substituted indoles. Georg Thieme Verlag Stuttgart.
- Palmieri, Alessandro,Petrini, Marino,Shaikh, Rafik R.
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scheme or table
p. 1845 - 1851
(2009/04/07)
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- Efficient N-tert-butoxycarbonylation of indoles with di-tert-butyl dicarbonate catalyzed by cesium fluoride
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An environmentally friendly process for the tert-butoxycarbonylation of indoles with di-tert-butyl dicarbonate has been developed. Catalytic amount of cesium fluoride can accelerate this tert-butoxycarbonylation. Georg Thieme Verlag Stuttgart.
- Inahashi, Nobuyuki,Matsumiya, Ayako,Sato, Tsuneo
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p. 294 - 296
(2008/12/21)
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- Ruthenium-catalyzed asymmetric hydrogenation of N-Boc-indoles
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Highly enantioselective hydrogenation of various N-Boc-indoles proceeded successfully in the presence of the ruthenium complex generated from an appropriate ruthenium precursor and a trans-chelate chiral bisphosphine PhTRAP. Various 2- or 3-substituted indoles were converted into chiral indolines with high enantiomeric excesses (up to 95% ee). The PhTRAP-ruthenium catalyst was able to promote the hydrogenation of 2,3-dimethylindoles, giving cis-2,3-dimethylindolines with 72% ee.
- Kuwano, Ryoichi,Kashiwabara, Manabu
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p. 2653 - 2655
(2007/10/03)
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- Novel pyridazinone derivatives as inhibitors of CDK2
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The present invention relates to compounds according to the general formula (I), with the definitions of the substituents X, R1 and R2 given below in the text, as well as their physiologically acceptable salts, methods for producing these compounds and their use as pharmaceuticals. These compounds are kinase inhibitors, in particular inhibitors of the kinase CDK2 (cyclin-dependent kinase 2)
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Page/Page column 24
(2008/06/13)
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- PYRIDAZINONE DERIVATIVES, METHODS FOR PRODUCING THEM AND THEIR USE AS PHARMACEUTICALS
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The present invention relates to compounds according to the general formula (I), with the definitions of the substituents X, R1 and R2 given below in the text, as well as their physiologically acceptable salts, methods for producing these compounds and their use as pharmaceuticals. Formula (I) These compounds are kinase inhibitors, in particular inhibitors of the kinase GSK-15 30 (glycogen synthase kinase-3?).
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Page/Page column 61
(2010/02/14)
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- New synthesis of 3-substituted indoles using lithium trimethylsilyldiazomethane
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Lithium trimethylsilyldiazomethane smoothly reacted with N-tosyl-o-acylanilines to give 3-substituted indoles in good to high yields.
- Miyagi, Takashi,Hari, Yoshiyuki,Aoyama, Toyohiko
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p. 6303 - 6305
(2007/10/03)
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- A new synthesis of 2-nitroindoles
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The C-2 lithiation of N-Boc- and N-(phenylsulfonyl)indoles (4-7) followed by reaction with dinitrogen tetroxide at low temperature affords the corresponding 2-nitroindoles 10-13 in 63-78% yields. Deprotection of the N-Boc-2-nitroindoles (10, 11) with trifluoroacetic acid gives 2-nitroindole (3) and 3-methyl-2-nitroindole (14) in essentially quantitative yields.
- Jiang, Jun,Gribble, Gordon W
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p. 4115 - 4117
(2007/10/03)
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- Total synthesis of tryprostatin A and B as well as their enantiomers
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The 3-methylindoles 3a, 3b were convened into tryprostatin A (1a), B (1b) and their enantiomers 2a, 2b via prenylation at the indole 2-position by generation of the required 2-lithioindole derivatives (from 7a, 7b), followed by alkylation.
- Zhao, Shuo,Gan, Tong,Yu, Peng,Cook, James M.
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p. 7009 - 7012
(2007/10/03)
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- Regiospecific Bromination of 3-Methylindoles with NBS and Its Application to the Concise Synthesis of Optically Active Unusual Tryptophans Present in Marine Cyclic Peptides
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A regiospecific bromination of substituted 3-methylindoles at either the C(3) alkyl moiety or the C(2) position was achieved via a free radical bromination or electrophilic process, respectively. The regiospecificity of the bromination could be controlled by variation of both the substituent and the N(1) protecting group on the indole ring. In addition, enantiospecific syntheses of 5-methoxytryptophan (20) and 5-hydroxy-6-chlorotryptophan (21c) as well as concise syntheses of optically active 2-bromotryptophan ethyl esters 26a,b or their substituted derivatives in three steps from bifunctional dibromoindoles were achieved via the above regiospecific process.
- Liu, Ruiyan,Zhang, Puwen,Gan, Tong,Cook, James M.
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p. 7447 - 7456
(2007/10/03)
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- Studies in the Protection of Pyrrole and Indole Derivatives
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Treatment of pyrrole (1a), 2,5-dimethylpyrrole (1b), indole (3a), 2-methylindole (3b), 3-methylindole (3c), 2,3-dimethylindole (3d), 1,2,3,4-tetrahydro-9H-carbazole (5a), 5,6,7,8,9,10-hexahydrocycloheptindole (5b), and 6,7,8,9,10,11-hexahydro-5H-cyclo-octindole (5c) with sodium hydride in tetrahydrofuran, followed by phenyl t-butyl carbonate (8) gives the corresponding N-t-butoxycarbonyl (t-BOC) derivatives in satisfactory yields.By using chlorodimethyl-t-butylsilane instead of (8), N-dimethyl-t-butylsilyl derivatives are obtained, also in satisfactory yields.The use of the 2-(trimethylsilyl)ethoxycarbonyl (TEOC) group for the N-protection of the indole system, and the pivaloyloxymethyl (POM) group for the N-protection of the pyrrole and indole systems is also described.
- Dhanak, Dashyant,Reese, Colin B.
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p. 2181 - 2186
(2007/10/02)
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