- Hydrogen/Halogen Exchange of Phosphines for the Rapid Formation of Cyclopolyphosphines
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The hydrogen/halogen exchange of phosphines has been exploited to establish a truly useable substrate scope and straightforward methodology for the formation of cyclopolyphosphines. Starting from a single dichlorophosphine, a sacrificial proton "donor phosphine"makes the rapid, mild synthesis of cyclopolyphosphines possible: reactions are complete within 10 min at room temperature. Novel (aryl)cyclopentaphosphines (ArP)5 have been formed in good conversion, with the crystal structures presented. The use of catalytic quantities of iron(III) acetylacetonate provides significant improvements in conversion in the context of diphosphine (Ar2P)2 and alkyl-substituted cyclotetra- or cyclopentaphosphine ((AlkylP)n, where n = 4 or 5) formation. Both iron-free and iron-mediated reactions show high levels of selectivity for one specific ring size. Finally, investigations into the reactivity of Fe(acac)3 suggest that the iron species is acting as a sink for the hydrochloric acid byproduct of the reaction.
- Barrett, Adam N.,Woof, Callum R.,Goult, Christopher A.,Gasperini, Danila,Mahon, Mary F.,Webster, Ruth L.
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supporting information
p. 16826 - 16833
(2021/11/04)
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- 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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- Tailored Cobalt-Catalysts for Reductive Alkylation of Anilines with Carboxylic Acids under Mild Conditions
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The first cobalt-catalyzed hydrogenative N-methylation and alkylation of amines with readily available carboxylic acid feedstocks as alkylating agents and H2 as ideal reductant is described. Combination of tailor-made triphos ligands with cobalt(II) tetrafluoroborate significantly improved the efficiency, thus promoting the reaction under milder conditions. This novel protocol allows for a broad substrate scope with good functional group tolerance, even in the presence of reducible alkenes, esters, and amides.
- Liu, Weiping,Sahoo, Basudev,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
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p. 11673 - 11677
(2018/09/10)
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- Rapid Metal-Free Formation of Free Phosphines from Phosphine Oxides
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A rapid method for the reduction of secondary phosphine oxides under mild conditions has been developed, allowing simple isolation of the corresponding free phosphines. The methodology involves the use of pinacol borane (HBpin) to effect the reduction while circumventing the formation of a phosphine borane adduct, as is usually the case with various other commonly used borane reducing agents such as borane tetrahydrofuran complex (BH3?THF) and borane dimethyl sulfide complex (BH3?SMe2). In addition, this methodology requires only a small excess of reducing agent and therefore compares favourably not just with other borane reductants that do not require a metal co-catalyst, but also with silane and aluminium based reagents. (Figure presented.).
- Provis-Evans, Cei B.,Emanuelsson, Emma A. C.,Webster, Ruth L.
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p. 3999 - 4004
(2018/09/21)
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- Copper-catalyzed C–P cross-coupling of secondary phosphines with (hetero)aromatic bromide
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A novel and convenient approach to the synthesis of various tertiary phosphines via a copper-catalyzed cross-coupling of (hetero)aromatic bromide with secondary phosphines has been developed. The reaction employs cheap copper as the catalyst, 2,6-bis(N-methylaminomethyl)pyridine (L4) as a perfect ligand and KOtBu as a base; all reactions are carried out under argon atmosphere. A variety of sterically hindered and/or functionalized substrates were found to react under these reaction conditions to provide products in good to excellent yields. Moreover, ten new tertiary phosphines were first reported in this process.
- Li, Chun-Jing,Lü, Jing,Zhang, Zhi-Xun,Zhou, Kun,Li, Yan,Qi, Guang-Hui
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p. 4547 - 4562
(2018/04/20)
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- Metal-Free Reduction of Phosphine Oxides, Sulfoxides, and N-Oxides with Hydrosilanes using a Borinic Acid Precatalyst
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The general reduction of phosphine oxides, sulfoxides, and amine N-oxides was achieved by combining bis(2-chlorophenyl)borinic acid with phenylsilane. The reaction was shown to tolerate a wide range of substrates and could be performed under mild conditions, with only 2.5 mol % of the easily synthesized catalyst. Mechanistic investigations pointed to a key borohydride as the real catalyst and at bis(2-chlorophenyl)borinic acid as a precatalyst.
- Chardon, Aurélien,Maubert, Orianne,Rouden, Jacques,Blanchet, Jér?me
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p. 4460 - 4464
(2017/11/22)
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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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- Catalyst-free alcoholysis of phosphane-boranes: a smooth, cheap, and efficient deprotection procedure
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Catalyst-free alcoholytic deprotection of borane-protected phosphorus compounds offers a smooth, efficient, and clean alternative to existing deprotection methods. In this paper we report our results on the general applicability of deprotecting phosphane-
- Van Overschelde, Michel,Vervecken, Elias,Modha, Sachin G.,Cogen, Simon,Van der Eycken, Erik,Van der Eycken, Johan
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experimental part
p. 6410 - 6415
(2009/12/09)
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- A catalytic method for the reduction of secondary and tertiary phosphine oxides
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TMDS has been found to be an efficient hydride source for the reduction of tertiary and secondary phosphine oxides using a catalytic amount of Ti(Oi-Pr)4. All classes of tertiary phosphine oxides, such as triaryl, trialkyl, and diphosphine, were effectively reduced. Georg Thieme Verlag Stuttgart.
- Berthod, Mika?l,Favre-Réguillon, Alain,Mohamad, Jahjah,Mignani, Gérard,Docherty, Gordon,Lemaire, Marc
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p. 1545 - 1548
(2008/02/05)
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- A METHOD FOR GENERATING SECONDARY PHOSPHINES
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This invention provides a method for generating secondary phosphines from secondary phosphine oxides in the presence of a reducing agent, such as diisobutylaluminum hydride (DIBAL-H), triisobutyldialuminoxane, triisobutylaluminum, tetraisobutyldialuminoxane, or another reducing agent comprising: (i) an R1R2AIH moiety, wherein R1 and R2 are each an alkyl species or oxygen, and wherein at least one of R1 or R2 comprises at least 2 carbon atoms, or (ii) an R1R2R3AI moiety, wherein R1, R2, and R3 are not hydrogen, and wherein at least one of R1, R2, and R3 is an alkyl species comprising a β-hydrogen, not including triethylaluminum. Preferred reducing agents for the present invention include: diisobutylaluminum hydride, triisobutyldialiuminoxane, triisobutylaluminum, tetraisobutyldialuminoxane, and combinations thereof.
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Page/Page column 12-13
(2008/06/13)
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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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- Electronic and steric effects of ligands as control elements for rhodium-catalyzed asymmetric hydrogenation
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Chiral diphosphine ligands analogous to bdpp have been synthesized and tested in order to study the effect of the electronic nature of the ligands in Rh-catalyzed asymmetric hydrogenation of some prochiral olefins. The results are compared with those obtained with the analogous unsubstituted ligand (bdpp). The rhodium-catalyzed asymmetric hydrogenation of olefins was influenced by ligand-based electronic effects, as well as substrate based ones. Excellent ee's (up to 98.3%) have been obtained in the rhodium-catalyzed hydrogenation of (Z)-α-acetamidocinnamic acids and esters.
- Herseczki, Zsanett,Gergely, Ildiko,Hegedues, Csaba,Szoellosy, Aron,Bakos, Jozsef
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p. 1673 - 1676
(2007/10/03)
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- Synthesis of achiral, but unsymmetric, seven-membered rhodium(I)-chelates for hydrogenation in the chiral environment of alkyl polyglucoside micelles
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Chiral rhodium(I) chelates containing a seven-membered ring are well-known active catalysts for the asymmetric hydrogenation of amino acid precursors. A high conformational flexibility allows their enantioselectivity to be strongly influenced by modifiers. Now we show the nature of the counter-ions to have a large influence in apolar solvents. In addition, the presence of micelle forming alkyl polyglycosides as amphiphiles causes a remarkable increase in the enantiomeric excess (%ee). However, on achiral catalysts this enantioselectivity inducing effect scarcely exceeds the standard deviation for the gas chromatographic determination of the enantiomeric ratio. This is also true for the application of unsymmetric P,P′-ligands such as 3-phosphinopropyl-phosphinites or butane-1,4-diyl-bis(phosphines) carrying different P′-aryl groups, for which synthetic routes are given.
- Fehring,Kadyrov,Ludwig,Holz,Haage,Selke
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p. 120 - 129
(2007/10/03)
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- Catalytic enantioselective conjugate addition of Grignard reagents to cyclic α,β-unsaturated carbonyl compounds
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A catalytic asymmetric conjugate addition reaction of organocopper reagents, generated from copper salt, a chiral phosphine, and Grignard reagent, with cyclohexenone is highly dependent on the counter anion of copper species, solvents, Grignard reagents,
- Kanai, Motomu,Nakagawa, Yuichi,Tomioka, Kiyoshi
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p. 3843 - 3854
(2007/10/03)
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- Reductive cleavage of the carbon-phosphorus bond with alkali metals. III Reactions of arylalkylphosphines
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The reductive cleavage of phenylalkylphosphines Ph2PR, PhPR2 (R = Bu, iPr) with Na/NH3 is unselective; both phenyl and alkyl groups can be cleavaged and Birch reduction may occur.Reaction of Ph2tBuP gives a high yield of diphenylphosphide.Polar groups (CO2Na, SO3Na) at the ω position of primary alkyl groups may lead to an increase in selectivity; Birch reduction is suppressed and a functionalised secondary phosphide is obtained.From diarylbenzyl- and diarylallylphosphines, the benzyl and allyl groups are selectively removed; Ar2PH and ArRPH are formed in high yield after hydrolytic work-up unless the aryl group bears F, CF3 or (CH3)2N substituents.From the reaction mixture of Ph2PCH2Ph we have isolated 1,2-diphenylethane. 2-Methoxyphenyl and 2,6-dimethoxyphenyl groups are selectively removed from Ar2BuP, ArPhBuP and Ar2P(CH2)3PAr2, forming ArBuPH, PhBuPH and ArP(H)(CH2)3(H)PAr, respectively.A double-cleavage reaction of Ar2RP may occur in low yield. 2,6-(dimethoxyphenyl-dibutylphosphine gives dibutylphosphine in moderate yield.When compounds with a 2,6-dimethoxyphenyl moiety are allowed to react with Li/THF, removal of a methyl group leads to novel phosphinophenols.It is concluded that cleavage of alkyl groups R selectively occurs when R radical is relatively stable (tBu, PhCH2> iPr > Bu).
- Doorn, Johannes A. van,Meijboom, Nico
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p. 170 - 177
(2007/10/02)
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- Reductive cleavage of the carbon-phosphorus bond with alkali metals. II. Cleavage of mixed functionalized triarylphosphines; Birch reduction of arylphosphines
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The reductive cleavage of mixed ortho- and para-functionalized triarylphosphines with Na/NH3 and Li/THF depends strongly on the nature and positions of the substituents.Reduction occurs readily with phosphines PhAr2P (4, 6 and 9) and Ph2ArP 19 when the corresponding phosphine Ar3P is not reduced.Cleavage of para-substituted compounds 7 and 9 leads to mixtures of secondary phosphines.By contrast, cleavage of mixed ortho-substituted triphenylphosphines is very selective.The functionalized phenyl group is split off in high yield when it carries CH3, (CH3)2N and CH3O substituents (2, 3, 5, 6, 8, 10, 11, 13, 14, 17, 19, 24, 25).Reaction of 4 is not selective due to loss of methoxy groups (1, 15, 16).The reactions of bis- and tris(diphenylphosphino)benzenes with Li/THF leads predominantly to cleavage of the diphenylphosphino group from the respective substrates.In a number of cases, the product of a Birch reduction with an isolated diene system is formed in NH3 (1, 9, 12, 21, 23) via a phosphino-stabilized cyclohexadienyl anion.This reduction does not occur in the aprotic solvent THF.Base-catalyzed isomerization leads to a conjugated double-bond system with a vinylphosphine moiety.We also report interesting large 4J(PP) couplings in 1,3-diphosphinobenzenes and complicated 13C resonances of para-substituted phosphines.
- Doorn, Johannes A. van,Frijns, John H. G.,Meijboom, Nico
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p. 441 - 449
(2007/10/02)
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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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- Chiral phosphines
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Novel substituted diphenyl tertiary phosphines of a pyrrolidine carboxylic acid derivative and their use as catalysts in the enantioselective hydrogenation of α-keto-β,β-dimethyl-γ-butyrolactone.
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