- Ru(II)-Catalyzed Amination of Aryl Fluorides via η6-Coordination
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We developed a Ru/hemilabile-ligand-catalyzed nucleophilic aromatic substitution (SNAr) of aryl fluorides as the limiting reagents. Significant ligand enhancement was demonstrated by the engagement of both electron-rich and neutral arenes in the SNAr amination without using excess arenes. Preliminary mechanistic studies revealed that the nucleophilic substitution proceeds on a η6-complex of the Ru catalyst and the substrate, and the hemilabile ligand facilitates dissociation of products from the metal center.
- Kang, Qi-Kai,Li, Yuntong,Lin, Yunzhi,Shi, Hang
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p. 3706 - 3711
(2020/03/11)
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- Facile, Catalytic Dehydrocoupling of Phosphines Using β-Diketiminate Iron(II) Complexes
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Catalytic dehydrocoupling of primary and secondary phosphines has been achieved for the first time using an iron pre-catalyst. The reaction proceeds under mild reaction conditions and is successful with a range of diarylphosphines. A proton acceptor is not needed for the transformation to take place, but addition of 1-hexene does allow for turnover at 50°C. The catalytic system developed also facilitates the dehydrocoupling of phenylphosphane and dicyclohexylphosphane. A change in solvent switches off dehydrocoupling to allow hydrophosphination of alkenes.
- King, Andrew K.,Buchard, Antoine,Mahon, Mary F.,Webster, Ruth L.
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supporting information
p. 15960 - 15963
(2015/11/03)
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- Selective dehydrocoupling of phosphines by lithium chloride carbenoids
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The development of a simple, transition-metal-free approach for the formation of phosphorus-phosphorus bonds through dehydrocoupling of phosphines is presented. The reaction is mediated by electronically stabilized lithium chloride carbenoids and affords a variety of different diphosphines under mild reaction conditions. The developed protocol is simple and highly efficient and allows the isolation of novel functionalized diphosphines in high yields.
- Molitor, Sebastian,Becker, Julia,Gessner, Viktoria H.
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p. 15517 - 15520
(2014/12/12)
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- NMR spectroscopy and structural characterization of dithiophosphinate ligands relevant to minor actinide extraction processes
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Synthetic routes to alkyl and aryl substituted dithiophosphinate salts that contain non-coordinating PPh4+ counter cations are reported. In general, these compounds can be prepared via a multi-step procedure that starts with reacting secondary phosphines, i.e. HPR2, with two equivalents of elemental S. The synthetic transformation proceeds by oxidation of the phosphine followed by insertion of S into the H-P bond. This approach was used to synthesize a series of dithiophosphinic acids that were fully characterized, namely HS2P(p-CF3C6H 4)2, HS2P(m-CF3C6H 4)2, HS2P(o-MeC6H4) 2 and HS2P(o-MeOC6H4)2. Although the insertion step was found to be much slower than the oxidation reaction, the formation of (NH4)S2PR2 from HPSR2 occurred rapidly upon addition of NH4OH. Subsequent cation exchange reactions proceeded readily with PPh4Cl in water, under air and at ambient conditions to provide analytically pure samples of [PPh4][S2PR2] (R = p-CF3C 6H4, m-CF3C6H4, o-CF 3C6H4, o-MeC6H4, o-MeOC6H4, Ph, and Me, 1b-7b, respectively), which were characterized by elemental analysis, multinuclear NMR, and IR spectroscopy. In addition, S2PPh2- and dithiophosphinates with ortho-substituted aryl groups (3b-6b) were characterized by X-ray crystallography. As opposed to the acids, which have short PS double bonds and long P-SH single bonds, the metric parameters for the S atoms in S 2PR2- are equivalent. In addition, the presence of large non-coordinating PPh4+ cations guard against intermolecular P-S...X interactions and ensure that the P-S bond is isolated. These S2PR2- anions, which can be prepared in large quantities and isolated in crystalline form, are attractive for spectroscopic and theoretical studies because the P-S interaction can be probed independently in the absence of intermolecular interactions.
- Daly, Scott R.,Klaehn, John R.,Boland, Kevin S.,Kozimor, Stosh A.,MacInnes, Molly M.,Peterman, Dean R.,Scott, Brian L.
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body text
p. 2163 - 2175
(2012/03/22)
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- Stereoelectronic factors in iron catalysis: Synthesis and characterization of aryl-substituted iron(II) carbonyl P-N-N-P complexes and their use in the asymmetric transfer hydrogenation of ketones
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A series of five (S,S)-trans-[Fe(CO)(Br)(PR2-CH 2CH=NCH(Ph)CH(Ph)N=CHCH2-PR2)][X] compounds (1a-c, X = BPh4; 1d,e, X = BF4) were synthesized and tested for the asymmetric transfer hydrogena
- Sues, Peter E.,Lough, Alan J.,Morris, Robert H.
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scheme or table
p. 4418 - 4431
(2011/10/10)
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- Synthesis of new serine-based phosphinooxazoline ligands and iridium complexes for asymmetric hydrogenations
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A series of serine-based phosphinooxazoline ligands was synthesized and the corresponding iridum complexes were successfully applied in the asymmetric hydrogenation of various unfunctionalized olefines and acetophenone-N-phenyl- imine. The results show that these new derivatives are useful substitutes for the standard tert-leucine-derived PHOX ligands.
- Franzke, Axel,Voss, Felix,Pfaltz, Andreas
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supporting information; experimental part
p. 4358 - 4363
(2011/08/03)
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- Convenient methods for the synthesis of a library of hemilabile phosphines
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A series of novel functionalized phosphines of hemilabile character, R 2P(CH2)nZ, have been prepared from diarylphosphines using several synthetic methodologies. The synthetic methods include the alkylation of lithium diar
- Jimenez, M. Victoria,Perez-Torrente, Jesus J.,Bartolome, M. Isabel,Oro, Luis A.
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body text
p. 1916 - 1922
(2009/12/28)
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- A superior method for the reduction of secondary phosphine oxides
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(Chemical Equation Presented) Diisobutylaluminum hydride (DIBAL-H) and triisobutylaluminum have been found to be outstanding reductants for secondary phosphine oxides (SPOs). All classes of SPOs can be readily reduced, including diaryl, arylalkyl, and dialkyl members. Many SPOs can now be reduced at cryogenic temperatures, and conditions for preservation of reducible functional groups have been found. Even the most electron-rich and sterically hindered phosphine oxides can be reduced in a few hours at 50-70°C. This new reduction has distinct advantages over existing technologies.
- Busacca, Carl A.,Lorenz, Jon C.,Grinberg, Nelu,Haddad, Nizar,Hrapchak, Matt,Latli, Bachir,Lee, Heewon,Sabila, Paul,Saha, Anjan,Sarvestani, Max,Shen, Sherry,Varsolona, Richard,Wei, Xudong,Senanayake, Chris H.
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p. 4277 - 4280
(2007/10/03)
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- Electron withdrawing substituents on equatorial and apical phosphines have opposite effects on the regioselectivity of rhodium catalyzed hydroformylation
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The electronic effects of electron withdrawing aryl substituents on equatorial and apical diphosphines were investigated. Chelating diphosphines designed to coordinate in diequatorial or in apical-equatorial positions were synthesized, and their effects on the regioselectivity of rhodium catalyzed 1-hexene hydroformylation were observed, Only diequatorial coordination was observed for 2,2'-bis[(diphenylphosphino)methyl]-1,1'-biphenyl (BISBI) complexes (BISBI)Ir(CO)2H (8) and [BISBI-(3,5-CF3)]Ir(CO)2H (10), and only apical-equatorial coordination was seen for 1,2-bis(diphenylphosphino)ethane (DIPHOS) complexes (DIPHOS)Ir(CO)2H (14) and [DIPHOS-(3,5-CF3)]Ir(CO)2H (15). For the trans-1,2-bis[(diphenylphosphino)methyl]cyclopropane (T-BDCP) complexes, a mixture of diequatorial and apical-equatorial complexes was seen. For (T-BDCP)Ir(CO)2H (12), 12-ae was favored over 12-ee by 63:37, but for [T-BDCP-(3,5-CF3)]Ir(CO)2H (13) the conformational preference was reversed and a 10:90 ratio of 13-ae:13-ee was seen. The electron withdrawing groups in the equatorial positions of BISBI-(3,5-CF3) (1) and T-BDCP-(3,5-CF3) (2) led to an increase in n-aldehyde regioselectivity in rhodium catalyzed hydroformylation. However, electron withdrawing aryl substituents in the apical positions of DIPHOS-(3,5-CF3) (3) led to a decrease in n-aldehyde regioselectivity in rhodium catalyzed hydroformylation.
- Casey, Charles P.,Lin Paulsen, Evelyn,Beuttenmueller, Eckart W.,Proft, Bernd R.,Petrovich, Lori M.,Matter, Brock A.,Powell, Douglas R.
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p. 11817 - 11825
(2007/10/03)
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- Reductive cleavage of the carbon-phosphorus bond with alkali metals. I. Cleavage of functionalised triphenylphosphines; formation of secondary and primary phosphines
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The reductive cleavage reaction of functionalised triphenylphosphines 1-34 with Na/NH3 and Li/THF depends strongly on the nature of the functionality and on the reducing agent. No reduction occurs with 11, 24, 30, 31 and 32 in Na/NH3.Compounds 3, 4, 5, 10, 12, 13, 15, 19, 23, 25, 26 and 27 cleave to give the secondary phosphide in high yield with Na/NH3, whereas 2, 7 and 9 give a high yield with Li/THF.Reduction occurs but cleavage is poor with 6, 7, 14, 29 and 34 and Na/NH3, or with 11 and Li/THF.Primary ortho-functionalised phenyl phosphines are obtained by a double cleavage reduction from 2, 5, 12, 25, 26 and 27 with Na/NH3.This unprecedented reaction proceeds via the secondary phosphine, which is formed by protonation of the corresponding phosphide with NH3.It occurs when the aryl group contains a strongly electron-donating substituent.Multiple cleavage of aryl groups with extended ? systems occurs with 7 and 34 when they are made to react with Li/THF.Halogens are cleaved from the phenyl group (16, 17, 18, 28 and 33, with Na/NH3), whereas SCH3 groups are converted to the corresponding mercapto group (20, 21 and 22).Birch reduction (2 and 10) can take place in NH3 but not in the aprotic solvent THF; it occurs only when other reactions are slow.Sodium amide is obtained via reaction of 8 in Na/NH3.Restricted Hartree-Fock calculations were carried out for a number of substituted phenylphosphines.From the correlation between the energies and coefficients of the LUMO (always an aryl ?* orbital) and the experimental cleavage data, it was concluded that there are three requirements for successful cleavage.The LUMO energy should be neither too high (no reduction) nor too low (radical anion too stable) and, further, the coefficient of the LUMO on the carbon attached to phosphorus must be large.
- Budzelaar, Peter H. M.,Doorn, Johannes A. van,Meijboom, Nico
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p. 420 - 432
(2007/10/02)
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