- How Radical Are "radical" Photocatalysts? A Closed-Shell Meisenheimer Complex Is Identified as a Super-Reducing Photoreagent
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Super-reducing excited states have the potential to activate strong bonds, leading to unprecedented photoreactivity. Excited states of radical anions, accessed via reduction of a precatalyst followed by light absorption, have been proposed to drive photoredox transformations under super-reducing conditions. Here, we investigate the radical anion of naphthalene monoimide as a photoreductant and find that the radical doublet excited state has a lifetime of 24 ps, which is too short to facilitate photoredox activity. To account for the apparent photoreactivity of the radical anion, we identify an emissive two-electron reduced Meisenheimer complex of naphthalene monoimide, [NMI(H)]-. The singlet excited state of [NMI(H)]- is a potent reductant (-3.08 V vs Fc/Fc+), is long-lived (20 ns), and its emission can be dynamically quenched by chloroarenes to drive a radical photochemistry, establishing that it is this emissive excited state that is competent for reported C-C and C-P coupling reactivity. These results provide a mechanistic basis for photoreactivity at highly reducing potentials via singlet excited state manifolds and lays out a clear path for the development of exceptionally reducing photoreagents derived from electron-rich closed-shell anions.
- Gonzalez, Miguel I.,Kudisch, Bryan,Nava, Matthew,Nocera, Daniel G.,Rieth, Adam J.
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supporting information
p. 14352 - 14359
(2021/09/15)
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- Photoinduced transition-metal and external photosensitizer free cross-coupling of aryl triflates with trialkyl phosphites
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Photoinduced phosphonation of aryl triflates with trialkyl phosphites via a tandem single-electron-transfer, C-O bond cleavage and Arbuzov rearrangement process in the absence of transition-metal and external photosensitizer is reported herein. The protoc
- Dou, Qian,Geng, Li,Cheng, Bin,Li, Chao-Jun,Zeng, Huiying
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supporting information
p. 8429 - 8432
(2021/09/02)
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- Flexible bifunctional monoethylphosphonate/carboxylates of Zn(ii) and Co(ii) reinforced with DABCO co-ligand: paradigmatic structural organization withpcutopology
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Two novel isostructural phosphonate-monoethylcarboxylate MOFs with the structural formula of [M2(EtBCP)2(DABCO)0.5]·2DMA (M = Zn (2), Co (3); H2EtBCP =O-ethyl-P-(4-carboxyphenyl)phosphonic acid, DABCO = 1,4-diazabicyclo[2.2.2]octane, DMA =N,N-dimethylacetamide) were synthesized and characterized. The frameworks of2and3are sustained by {Zn2(PO2(OEt))2}nmetal-phosphonate- and DABCO-extended {Zn2(COO)4(DABCO)}npaddle-wheel carboxylate chain-SBUs. The chains providing connectivity in three, mutually orthogonal directions are running parallel and are combined in a framework, which could be interpreted as having apcutopology. The simple structure-organization principle, which suggests the possibility of the elongation of the bifunctional ligand with scaling in two directions, allows to view the structures of2and3as prototypes for an isoreticular series. The porosity of both compounds, based on a relatively short ligand, is low: no adsorption of N2was registered, however, CO2is adsorbed readily allowing to estimate the surface area at ~330 m2g?1(~900-1060 m2g?1geometric estimate). The compounds demonstrate a two-step CO2adsorption isotherm both at 195 K (0-1 bar) and 298 K (0-20 bar). The adsorption isotherms are characterized by a gradual (type “F-I”), albeit still relatively steep onset of the second step, associated with structural flexibility/bistability. The estimated pore volumes at the start of the transformation (195 K) for2and3are ~0.11 (0.08P/P0) and 0.12 cm3g?1(0.12P/P0) respectively, which corresponds considerably well to the geometrically calculated accessible volume of ~0.07 cm3g?1for the experimental structure (3.3 ? probe diameter). The structural prerequisites of the observed flexibility of the framework, which might be associated with the non-planarity of the metal-phosphonate moieties, acting as ‘levers’ for propagating mechanical stress, are discussed.
- Boldog, Ishtvan,G?kpinar, Serkan,Gil-Hernández, Beatriz,Goldman, Anna,Heering, Christian,Janiak, Christoph,Millan, Simon
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p. 2933 - 2944
(2020/05/18)
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- Catalyst-free phosphorylation of aryl halides with trialkyl phosphites through electrochemical reduction
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A catalyst-free electrochemical cross-coupling reaction of aryl halides with trialkyl phosphite has been developed. This reaction proceeds in an undivided cell with a low-cost Ni anode and a graphite cathode under mild and neutral conditions. A wide range of functional groups are well-tolerated and the phosphorylated product can be obtained on the gram scale, showing that this transformation has the potential to be a valuable method for the construction of aromatic carbon-phosphorus bonds.
- Wang, Shuai,Yang, Cheng,Sun, Shuo,Wang, Jianbo
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supporting information
p. 14035 - 14038
(2019/11/25)
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- Decarbonylative Phosphorylation of Carboxylic Acids via Redox-Neutral Palladium Catalysis
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We describe the direct synthesis of organophosphorus compounds from ubiquitous aryl and vinyl carboxylic acids via decarbonylative palladium catalysis. The catalytic system shows excellent scope and tolerates a wide range of functional groups (>50 examples). The utility of this powerful methodology is highlighted in the late-stage derivatization directly exploiting the presence of the prevalent carboxylic acid functional group. DFT studies provided insight into the origin of high bond activation selectivity and P(O)-H isomerization pathway.
- Liu, Chengwei,Ji, Chong-Lei,Zhou, Tongliang,Hong, Xin,Szostak, Michal
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supporting information
p. 9256 - 9261
(2019/11/19)
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- Decarbonylative Phosphorylation of Amides by Palladium and Nickel Catalysis: The Hirao Cross-Coupling of Amide Derivatives
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Considering the ubiquity of organophosphorus compounds in organic synthesis, pharmaceutical discovery agrochemical crop protection and materials chemistry, new methods for their construction hold particular significance. A conventional method for the synthesis of C?P bonds involves cross-coupling of aryl halides and dialkyl phosphites (the Hirao reaction). We report a catalytic deamidative phosphorylation of a wide range of amides using a palladium or nickel catalyst giving aryl phosphonates in good to excellent yields. The present method tolerates a wide range of functional groups. The reaction constitutes the first example of a transition-metal-catalyzed generation of C?P bonds from amides. This redox-neutral protocol can be combined with site-selective conventional cross-coupling for the regioselective synthesis of potential pharmacophores. Mechanistic studies suggest an oxidative addition/transmetallation pathway. In light of the importance of amides and phosphonates as synthetic intermediates, we envision that this Pd and Ni-catalyzed C?P bond forming method will find broad application.
- Liu, Chengwei,Szostak, Michal
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p. 12718 - 12722
(2017/10/06)
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- The Cu-catalyzed C-P coupling of phosphonate esters with arylboronic acids
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Copper-catalyzed C-P cross coupling of phosphonate esters with arylboronic acids has been developed. The reaction provided an efficient method for aryl phosphonates under mild conditions.
- Wan,Zhao,Wang,Zhang,Li
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p. 150 - 153
(2016/03/12)
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- A dual catalytic strategy for carbon-phosphorus cross-coupling via gold and photoredox catalysis
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A new method for the P-arylation of aryldiazonium salts with H-phosphonates via dual gold and photoredox catalysis is described. The reaction proceeds smoothly at room temperature in the absence of base and/or additives, and offers an efficient approach t
- He, Ying,Wu, Hongmiao,Toste, F. Dean
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p. 1194 - 1198
(2015/01/30)
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- An improved procedure for the synthesis of aryl phosphonates by palladium-catalysed cross-coupling of aryl halides and diethyl phosphite in polyethylene glycol
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A general and greener protocol for the synthesis of aryl phosphonates by the cross-coupling of aryl halides and diethyl phosphite using tetrakis(triphenylphosphine)palladiume/triethylamine/polyethylene glycol 600 [Pd(PPh3)4/ Et3N/PEG 600] as an efficient catalytic system has been developed. This procedure also avoids hazardous solvents and is therefore an eco-friendly alternative to the existing methods.
- Wang, Ping,Lu, Jie,Zhang, Zhan-Hui
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p. 359 - 361
(2013/07/26)
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- Nickel-catalyzed Arbuzov reactions of aryl triflates with triethyl phosphite
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An efficient method was developed for the nickel-catalyzed phosphonylation of aryl triflates with triethyl phosphite, in which KBr as an additive promoted the SN2 catalytic step. To the best of our knowledge, this is the first example of nickel
- Yang, Guoqiang,Shen, Chaoren,Zhang, Liang,Zhang, Wanbin
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supporting information; experimental part
p. 5032 - 5035
(2011/10/09)
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- Copper-catalyzed C-P bond construction via direct coupling of phenylboronic acids with H-phosphonate diesters
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A mild and efficient method was developed for the copper-catalyzed additions of H-phosphonate diesters to boronic acids under the copper catalyst system Cu2O/1,10-phenanthroline. To the best of our knowledge this finding is the first example of a copper-catalyzed synthesis of aryl phosphonates from arylboronic acids and H-phosphonate dialkyl esters.
- Zhuang, Rongqiang,Xu, Jian,Cai, Zhenshi,Tang, Guo,Fang, Meijuan,Zhao, Yufen
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supporting information; experimental part
p. 2110 - 2113
(2011/06/20)
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- Manganese(III)-mediated direct phosphonylation of arenes
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Manganese (III)-promoted direct phosphonylation of mono- and disubstituted arenes with dialkylphosphite afforded regioselective dialkylphosphonates in good yields. The reactions can apply to arenes bearing electron-donating groups and electron-withdrawing
- Xu, Wei,Zou, Jian-Ping,Zhang, Wei
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experimental part
p. 2639 - 2643
(2010/06/16)
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- Microwave-promoted palladium(II)-catalyzed C-P bond formation by using arylboronic acids or aryltrifluoroborates
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The first PdII-catalyzed P arylation has been performed by using palladium acetate, the rigid bidentate ligand dmphen (dmphen=2,9-dimethyl-1,10- phenanthroline), and without the addition of base or acid. Couplings of arylboronic acids or aryl t
- Andaloussi, Mounir,Lindh, Jonas,Saevmarker, Jonas,Sjoeberg, Per J. R.,Larhed, Mats
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supporting information; experimental part
p. 13069 - 13074
(2010/05/19)
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- Palladium-Catalyzed Phase-Transfer Arylation of Dialkyl Phosphonates
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Palladium-catalyzed phase-transfer arylation of dialkyl phosphonates with various iodo- and bromoarenes has been studied. The arylation has also been effected in the absence of ligand. A simple preparative procedure for synthesizing arylphosphonic acids has been developed.
- Kabachnik,Solntseva,Izmer,Novikova,Beletskaya
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- Rapid and efficient phosphonation of aryl halides catalysed by palladium under microwaves irradiation
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Diethyl arylphosphonates are efficiently and rapidly prepared from aryl halides, by a palladium catalysis, performed in a Teflon autoclave under microwave radiation generated by a commercial microwave oven.
- Villemin, Didier,Jaffres, Paul-Alain,Simeon, Fabrice
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- Arylphosphonic acids. I. Substituent effects on their first and second dissociations
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Thermodynamic pK1 and pK2 values of 36 arylphosphonic acids have been determined.The pK values of the meta and para compounds are correlated well by the ?n parameter, suggesting that there is little conjugation between the
- Nagarajan, K.,Shelly, Kevin P.,Perkins, R. R.,Stewart, Ross
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p. 1729 - 1733
(2007/10/02)
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- PALLADIUM-CATALYZED NEW CARBON-PHOSPHORUS BOND FORMATION
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Dialkyl arylphosphonates are prepared by the palladium-catalyzed reaction of aryl bromides with dialkyl phosphite in the presence of triethylamine.The similar treatment of vinyl bromides gives dialkyl vinylphosphonates stereoselectively.
- Hirao, Toshikazu,Masunaga, Toshio,Yamada, Naoto,Ohshiro, Yoshiki,Agawa, Toshio
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p. 909 - 913
(2007/10/02)
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