- 2-Phenoxyethyldiphenylphosphine oxide as an equivalent of diphenylvinylphosphine oxide in nucleophilic additions
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A facile method for the synthesis of β-functionalized ethyldiphenylphosphine oxides is developed based on readily available 2-phenoxyethyldiphenylphosphine oxide used as an equivalent of diphenylvinylphosphine oxide in the reactions of addition of different PH- and NH-nucleophiles in DMSO in the presence of KOH. The transformations of labile phosphine oxides of a general formula Ph2P(O)CH2CH2OR, where R = Ph, H, or Ph2P(O)CH = CH2, in aq.KOH/DMSO and solid KOH/DMSO systems are explored in the absence of nucleophilic reagents.
- Bondarenko, Natalia A.,Tcarkova, Kseniia V.,Belus', Svetlana K.,Artyushin, Oleg I.
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p. 902 - 910
(2021/06/25)
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- Diastereoselective Rhodium Catalyzed [4 + 2] Cycloisomerization of Allenes
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A diastereoselective [4 + 2] cycloisomerization of asymmetric allenyl dienes is reported. The asymmetric dienyl allenes are synthesized using the method reported by Ma. These substrates readily undergo diastereoselective intramolecular rhodium catalyzed [4 + 2] cycloisomerization analogous to thermal intramolecular Diels-Alder reactions. Overall, 29 examples are presented with tethers possessing nitrogen, oxygen, and carbon. Diastereoselectivities range from 99:1 to 90:10 in most examples.
- Li, Jun,Gilbertson, Scott R.
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supporting information
p. 2911 - 2914
(2021/05/05)
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- 31P NMR spectroscopic analysis on photooxidation of 1,n-bis(diphenylphosphino)alkanes with the aid of DFT calculations
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The chloroform-d solution of diphosphine, 1,n-bis(diphenylphosphino)alkane (Ph2P(CH2)nPPh2; n = 1-6), was photolyzed with light from a xenon lamp in air. The progress of the reaction was followed by 31P NMR spectroscopy. The observed spectral change showed that the diphosphine is initially oxidized to diphosphine monoxide, Ph2P(═O)(CH2)nPPh2, which is further oxidized to diphosphine dioxide, Ph2P(═O)(CH2)nP(═O)Ph2. The oxidation of the diphosphine to the diphosphine monoxide took place according to first-order kinetics with respect to the concentration of the diphosphine, the first-order rate constant, kobs, being larger with increasing number of the methylene units in the spacer. The observation in kinetics is interpreted based on the conformation of the diphosphine radical cation intermediate initially generated by electron transfer from the photoexcited diphosphine to oxygen. Density functional theory (DFT) calculations predict that the diphosphine radical cation takes “folded” conformation where two phosphorus atoms are arranged closely to each other. The “folded” conformer of the diphosphine radical cation results from electrostatic interaction of these two phosphorus atoms. This conformer explains the observed dependency of kobs on the length of the spacer in the diphosphine.
- Yasui, Shinro,Yamazaki, Shoko
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- Acetylacetonate and Acetate Complexes of Nickel(II) Catalyse the Air Oxidation of Phosphines
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The polymeric complex trans-[Ni(acac)2(μ2-dppe)]n·2MeCN {1a, dppe = 1,2-ethylenebis(diphenylphosphine)} is sometimes transiently deposited from the reaction of [Ni(acac)2] with dppe in MeCN prior to its facile onwards air oxidation to final crystallization of a doubly-oxygenated relative, cis-[Ni(acac)2(μ2-dppeO2)]n {2, dppeO2 = 1,2-ethylenebis(diphenylphosphineoxide)}. A similar unsolvated phase of the initial polymer, trans-[Ni(acac)2(μ2-dppe)]n (1b), can be isolated from toluene. The oxidation of dppe by O2 is catalytic and dppeO2 was isolated in close to stoichiometric yields from solutions containing 5 % Ni(acac)2 relative to dppe. The reaction rate slows after a few turnovers due to inhibition by the product. The relative yields of dppeO2 are higher than those from catalytic air oxidation of methyldiphenylphosphine and triphenylphosphine and we speculate that a pathway for this reaction involves a dimetallic cooperativity enabled specifically by dppe.
- Hansen, Line Sofie,Jakobsen, Vibe Boel,McKee, Vickie,McKenzie, Christine J.
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p. 4163 - 4169
(2020/10/12)
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- Chemoselective Reduction of Phosphine Oxides by 1,3-Diphenyl-Disiloxane
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Reduction of phosphine oxides to the corresponding phosphines represents the most straightforward method to prepare these valuable reagents. However, existing methods to reduce phosphine oxides suffer from inadequate chemoselectivity due to the strength of the P=O bond and/or poor atom economy. Herein, we report the discovery of the most powerful chemoselective reductant for this transformation to date, 1,3-diphenyl-disiloxane (DPDS). Additive-free DPDS selectively reduces both secondary and tertiary phosphine oxides with retention of configuration even in the presence of aldehyde, nitro, ester, α,β-unsaturated carbonyls, azocarboxylates, and cyano functional groups. Arrhenius analysis indicates that the activation barrier for reduction by DPDS is significantly lower than any previously calculated silane reduction system. Inclusion of a catalytic Br?nsted acid further reduced the activation barrier and led to the first silane-mediated reduction of acyclic phosphine oxides at room temperature.
- Buonomo, Joseph A.,Eiden, Carter G.,Aldrich, Courtney C.
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supporting information
p. 14434 - 14438
(2017/10/23)
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- 2-Pyridyl-phosphine and -diphosphine complexes of nickel(0), their reactivity (including aqueous solution chemistry), and some related, incidental methylphosphonium iodides
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The chemistry of Ni0-dicarbonyl(pyridylphosphine) complexes of the type Ni(CO)2L2, where L is either P-bonded PPh3-npyn (n = 1-3, py = 2-pyridyl; abbreviated PNx, x = 1-3, species 1a-c), or L2 is (P-P)-chelated py2P(CH2)2Ppy2 or, is further developed from earlier studies by our group [the P-P ligands are abbreviated, respectively, as d(py)pe and d(py)pcp]. The complexes are synthesized from C6H6 solutions of Ni(CO)2(PPh3)2, and the Ni(CO)2(PPh3)(PNx) intermediates (1a-c) are detected; Ni(CO)2[d(py)pcp] (2b) is shown by X-ray analysis to have a distorted tetrahedral structure; and the NiII species [Ni2(CO)4(μ-PN2)2]Cl4 is isolated from a light-induced reaction in CDCl3 solution. Complex 2b dissolves in water at ambient conditions via a net double protonation of pyridyl N-atoms, the {Ni(CO)2[2H-d(py)pcp]}2+ being isolated as the bis(triflate) salt; the dication decomposes in minutes with formation of [Ni(H2O)6]2+, CO, the phosphine dioxide, and deprotonated d(py)pcp. Some twenty-two Ni0 complexes, exemplified by Ni(P-P)2, Ni(PNx)2(P-P), Ni(PNx)4, and related PPh3- and Ph2P(CH2)2PPh2 (dppe)-containing species, are synthesized from Ni(1,5-COD)2 and their reactivity studied; for example, oxidative addition of MeI generates trans-Ni(Me)(I)(PN3)2 and trans-Ni(Me)(I)(P-P)2 but, with non-pyridyl containing reactants such as Ni(PPh3)4 and Ni(dppe)2, only (monomethyl)phosphonium iodides are formed. Such iodides, and the bis(methyl) analogues [(CH3)2(diphosphine)]I2, are then studied for clarification of some observed Ni chemistry. The NMR trends (a)-(d) are noted within the series of Ni0 complexes, and are rationalized: (a) the 2JPP values in 1a-c, and the separation between the two doublets, parallel the number of N-atoms present; (b) the 31P{1H} signals in the Ni(PNx)4 and Ni(PNx)2(P-P) complexes shift downfield in the order PN1 2 3 within linear dependences; (c) the 2JPP values for the Ni(PR3)2(P-P) complexes (R = Ph and PNx) decrease in the order R = Ph > PN1 > PN2 > PN3; (d) and the separation between the two 31P{1H} triplets of the Ni(PNx)2(P-P) complexes generally depends on the relative numbers of phenyl and pyridyl groups.
- Le Page, Matthew D.,Patrick, Brian O.,Rettig, Steven J.,James, Brian R.
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p. 276 - 288
(2015/06/02)
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- Intramolecular stabilization of the phosphine radical cation by the second phosphorus atom during the photooxidation of diphosphines:31P NMR spectroscopic analysis
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Diphosphines, Ph2P(CH2)nPPh2 1 (n = 1, 2, 3, 4, and 6), were photolyzed by a xenon lamp in air. The 31P NMR spectroscopic analysis of the reaction showed that 1 is oxidized, according to first-order kinetics, to the monoxide, which is further oxidized to the dioxide. The dependence of the rate constants for the first oxidation on the chain-length n in 1 is interpreted in terms of the orientation of the p-orbitals on the two phosphorus atoms in the intermediate, the diphosphine radical cation.
- Yasui, Shinro,Yamazaki, Shoko
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p. 422 - 424
(2015/05/27)
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- Selective mono reduction of bis-phosphine oxides under mild conditions
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Bis-phosphine oxides can be selectively reduced to bis-phosphine monoxides under exceptionally mild conditions using triflic anhydride and a thiol. The Royal Society of Chemistry.
- Petersson, Maria J.,Loughlin, Wendy A.,Jenkins, Ian D.
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experimental part
p. 4493 - 4494
(2009/05/06)
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