- Stable Fe(ii)-based coordination polymers: Synthesis, structural diversity and catalytic applications in homo-coupling reactions
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Herein, we synthesize three new stable Fe(ii) coordination polymers, {[Fe3(tttmb)4(OH)(NCS)5]2CH3OH·H2O}n (1), {[Fe3(tttmb)4(NCS)6]·3H2O}n (2), and {[Fe3(tttmb)2Cl6(H2O)6]·5H2O}n (3) (tttmb = 1,3,5-tris(triazole-1-ylmethyl)-2,4,6-trimethyl-benzene) under the regulation of KSCN and solvents and use them as green heterogeneous catalysts in aryl homo-coupling reactions. The catalytic experiments show that 1 and 3 exhibit high efficiency for aryl homo-coupling reactions under an air environment with a yield of up to 80%. Furthermore, the crystal structure analysis reveals that 1 and 3 have coordinated water molecules and OH-, which are easily removed from the host materials during the reactions. In contrast, no unsaturated coordination sites are generated in 2 during the reaction process. In addition, the variable temperature magnetic susceptibilities of 1-3 prove that the metal centers of these polymers are bivalent and all of them exhibit a weak antiferromagnetic effect.
- Wu, Qiong,Han, Yanbing,Shao, Zhichao,Li, Junxia,Hou, Hongwei
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p. 8063 - 8069
(2018/06/26)
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- Homocoupling of iodoarenes and bromoalkanes using photoredox gold catalysis: A light enabled Au(III) reductive elimination
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The formation of homocoupled alkane byproducts have been identified in the reduction of bromoalkanes via photoredox gold catalysis with dimeric Au(I) complexes. This prompted further investigation into the mechanism of formation of these byproducts and the diversity of C-X bonds amenable to this transformation. Examples were found when considering bromoalkanes while a wide variety of iodoarenes underwent this process in good to excellent yields. The light enabled homocoupling of iodoarenes made possible by photoredox gold catalysis is reported.
- Tran, Huy,McCallum, Terry,Morin, Mathieu,Barriault, Louis
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supporting information
p. 4308 - 4311
(2016/09/09)
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- Pd-catalyzed cross-coupling study of bi-functional 3-bromo-4-trifloxycoumarins with triarylbismuth reagents
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Abstract The cross-coupling reactions of functionalized 3-bromo-4-trifloxycoumarins have been explored with threefold arylating triarylbismuth reagents. These palladium-catalyzed reactions afforded chemo-selective C-4 arylations with the facile formation of 3-bromo-4-arylcoumarins in good to high yields. Additionally, palladium-catalyzed arylations of functionalized 3-bromo-4-arylcoumarins also participated in the second arylation to give functionalized 3,4-diarylcoumarins in high yields.
- Rao, Maddali L.N.,Kumar, Abhijeet
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p. 5137 - 5147
(2015/06/30)
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- Imino-N-heterocyclic carbene palladium(ii) complex-catalyzed direct arylation of electron-deficient fluoroarenes with "on and off" chelating effect assistance
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An imino-N-heterocyclic carbene palladium(II) complex with a bulky substituted group on the imino nitrogen was used to catalyze the direct arylation of electron-deficient fluoroarenes with aryl halides. A series of electron-poor substrates and aryl bromides could be coupled in good to excellent yields with satisfactory position selectivity (20 examples, up to 93%). These arylations could proceed at a relatively low temperature (80 °C, 20 examples, up to 95%) with mono-N-protected amino acid assistance. Some of them even gained higher yields than those at high temperature (110 °C). Otherwise, some aryl iodides can forge cross-coupling products in yields of nearly 30% under the optimized conditions. The rate profiles for arylation of electron-poor arenes were measured in the presence of the imino-N-heterocyclic carbene palladium(II) complex or Pd(OAc)2 as the catalyst, which showed that the former could keep catalytic activity for a longer time. Computational studies indicated that the imino nitrogen in the imino-N-heterocyclic carbene ligand can detach from and attach to the central metal in the catalytic cycle. Thus, the coordination site could be protected, and this effect may be responsible for decreasing the rate of palladium black formation.
- Zhou, Quan,Wang, Ya-Nong,Guo, Xu-Qing,Zhu, Xiao-Han,Li, Zhi-Ming,Hou, Xiu-Feng
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p. 1021 - 1028
(2015/03/31)
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- Pd-catalyzed chemo-selective mono-arylations and bis-arylations of functionalized 4-chlorocoumarins with triarylbismuths as threefold arylating reagents
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Cross-coupling reactions of differently substituted 4-chlorocoumarins were studied under palladium catalysis using triarylbismuths as threefold arylating reagents. The high reactivity of 4-chlorocoumarins was demonstrated delivering mono- and bis-arylation products in a chemo-selective manner. The reaction conditions employed are simple, robust and the threefold coupling reactivity of triarylbismuth reagents was witnessed with good to high yields in 2-4 h conditions. The utility of the methodology was explored in the synthesis of a few natural occurring neoflavones (3.27-3.30). In addition, the 4-arylcoumarin 3.1 product is a useful precursor for the preparation of (R)-tolterodine.
- Rao, Maddali L.N.,Kumar, Abhijeet
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p. 6995 - 7005
(2015/03/14)
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- Pd-catalyzed tandem chemoselective synthesis of 2-arylbenzofurans using threefold arylating triarylbismuth reagents
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A tandem chemoselective synthesis of 2-arylbenzofurans was accomplished from o-hydroxy-gem-(dibromovinyl)benzenes and BiAr3 reagents under palladium-catalyzed conditions. This unique and synthetically valuable strategy proceeds through three consecutive coupling reactions involving triarylbismuth reagents and provides 2-arylbenzofuran products in high yields. A tandem chemoselective synthesis of 2-arylbenzofurans was accomplished from o-hydroxy-gem-(dibromovinyl)benzenes and BiAr3 reagents under palladium-catalyzed conditions. This unique and synthetically valuable strategy proceeds through three consecutive coupling reactions involving triarylbismuth reagents and provides 2-arylbenzofuran products in high yields. Copyright
- Rao, Maddali L. N.,Jadhav, Deepak N.,Dasgupta, Priyabrata
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p. 781 - 788
(2013/03/13)
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- Palladium-catalyzed cross-couplings of functionalized 2-bromobenzofurans for atom-economic synthesis of 2-arylbenzofurans using triarylbismuth reagents
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The palladium catalyzed, atom-economic synthesis of various functionalized 2-arylbenzofurans was achieved through cross-coupling reaction of 2-bromobenzofurans with triarylbismuth reagents. The palladium catalytic protocol is very efficient to furnish various cross-coupled functionalized 2-arylbenzofurnas in high yields using triarylbismuth reagents with three aryl couplings as multi-coupling organometallic nucleophiles in one-pot operation. All the coupling reactions were completed in 1 h short reaction time involving three couplings from triarylbismuths under heating condition.
- Rao, Maddali L.N.,Awasthi, Dheeraj K.,Talode, Jalindar B.
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supporting information; experimental part
p. 2662 - 2666
(2012/07/02)
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- Synthesis of functionalized 2-arylthiophenes with triarylbismuths as atom-efficient multicoupling organometallic nucleophiles under palladium catalysis
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Atom-efficient cross-coupling reactions of functionalized 2-bromo- and 2-iodothiophenes have been demonstrated using triarylbismuths as atom-efficient multicoupling organometallic nucleophiles under palladium-catalyzed conditions. These couplings with various functionalized triarylbismuths proceeded smoothly to afford the corresponding functionalized 2-arylthiophenes in high yields. Georg Thieme Verlag Stuttgart · New York.
- Rao, Maddali L. N.,Banerjee, Debasis,Dhanorkar, Ritesh J.
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supporting information; experimental part
p. 1324 - 1330
(2011/07/07)
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- Pd-catalyzed domino synthesis of internal alkynes using triarylbismuths as multicoupling organometallic nucleophiles
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Figure presented The domino coupling reaction of 1,1-dibromo-1-alkenes with triarylbismuth nucleophiles has been demonstrated to furnish disubstituted alkynes directly under catalytic palladium conditions. The couplings of triarylbismuths as multicoupling nucleophiles with 3 equiv of 1,1-dibromo-1-alkenes are very fast, affording high yields of alkynes in a short reaction time. Thus, an efficient domino process has been accomplished using 1,1-dibromo-1-alkenes as surrogates for internal alkyne synthesis in couplings with triarylbismuths in a one-pot operation.
- Rao, Maddali L. N.,Jadhav, Deepak N.,Dasgupta, Priyabrata
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supporting information; experimental part
p. 2048 - 2051
(2010/07/03)
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- Polymer-Assisted Solution-Phase (PASP) Suzuki Couplings Employing an Anthracene-Tagged Palladium Catalyst
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A general method for polymer-assisted solution-phase (PASP) Suzuki reactions employing a combination of anthracene-tagged palladium catalyst and anthracene-tagged boronic acid with a polymer-supported carbonate base is reported. The anthracene-tagged catalyst allows for the easy removal of the Pd catalyst along with the dissociated phosphine ligand and phosphine oxide byproducts by sequestration through a chemoselective Diels-Alder reaction with a maleimide resin. The polymer-supported carbonate base facilitates the removal of excess boronic acid and the borane-containing byproducts present at the end of the coupling reaction. The Suzuki coupling reaction can be efficiently conducted by using combinations of the anthracene-tagged Pd catalyst, polymer-supported carbonate base, and anthracene-tagged boronic acid to yield the desired product in high purity and yield without the use of chromatography.
- Lan, Ping,Berta, Daniela,Porco Jr., John A.,South, Michael S.,Parlow, John J.
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p. 9678 - 9686
(2007/10/03)
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- Evidence for the Occurrence of Substitution Side Products in Grignard Reactions
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In the formation of Grignard reagents from 4-bromoalkoxybenzene and their subsequent coupling reactions with allylic halides, the unusual minor side products, 8 - 14 have been obtained.
- Lajis, Nordin Hj.,Khan, Mohammad Niyaz,Hassan, Hazimah A.
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p. 3405 - 3410
(2007/10/02)
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- PHOTOLYSIS OF ARYL ESTERS OF TRI- AND TETRACOORDINATED PHOSPHORUS COMPOUNDS
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Upon UV excitation in methanol, some diaryl esters of alkly- or alkenyl phosphonates underwent an elimination of two aryl groups to give biaryls and the corresponding alkyl- or alkenylphosphonic acids.Tris(4-methoxyphenyl) phosphite also underwent a similar elimination to give 4,4'-dimethoxybiphenyl and 4-methoxyphenyl phosphonate.This interesting biaryl elimination was confirmed to proceed via a singlet intramolecular excimer by means of fluorescence spectra and Stern-Volmer analysis.
- Shi, Min,Yamamoto, Kiichi,Okamoto, Yoshiki,Takamuku, Setsuo
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- Selective Synthesis of Unsymmetrical Biaryls via Palladium-Catalyzed Cross-Coupling of Arylfluorosilanes with Aryl Iodides
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In the presence of potassium fluoride, arylfluorosilanes readily participate in Pd-catalyzed cross-coupling reaction of aryl iodides to give the corresponding unsymmetrical biaryls in good yields.
- Hatanaka, Yasuo,Fukushima, Satoshi,Hiyama, Tamejiro
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p. 1711 - 1714
(2007/10/02)
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- Unsymmetrical Anodic Coupling of Veratrole with Various Anisole Derivatives. Products and Mechanisms
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The coelectrolysis of veratrole (1) with anisole (2a), phenetole (2b), 3-methylanisole (2c), 2-methylanisole (3), 2,5-dimethylanisole (4), and 2,6-dimethylanisole (6) have been investigated in trifluoroacetic acid-dichloromethane solvent.With 2a-c good yields of "tetrameric" 5-aryl substituted triphenylene derivatives (10a, 10b or 11) were obtained, probably by initial coupling of the veratrol cation radical (1.+) with the anisole derivative or its cation radical to an unsymmetrical dimer (8 or 11) followed by dimerisation and intramolecular cyclisation to the product.With 3,4 or 5 only "trimeric" products from coupling of two veratrole units with one of the anisole units (15 or 26) or from coupling of one veratrole unit with two of the anisole units (17,22,25 or 27) were observed.
- Ronlan, Alvin,Aalstad, Bjoerg,Parker, Vernon D.
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p. 317 - 326
(2007/10/02)
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