Taniaphos and Walphos ligands: Oxidative electrochemistry and complexation. Synthesis, characterization, oxidative electrochemistry and X-ray structures of [(Taniaphos/Walphos)MCl2] (M=Pd or Pt)

Maddox, Annalese F.; Rheingold, Arnold L.; Golen, James A.; Kassel, W. Scott; Nataro, Chip

doi:10.1016/j.ica.2007.09.031

Cited by 10 publications

(10 citation statements)

References 47 publications

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“…First, to determine the coordination mode of Taniaphos ( 3 ) with silver(I), we isolated and studied by X‐ray diffraction the complex [AgOAc( 3 )], prepared by treatment of Taniaphos 3 with AgOAc in THF and further recrystallisation in CH 2 Cl 2 /hexane22 (Figure 2). This complex shows a P,P‐bidentate coordination to silver, similar to that found in Pt II –Taniaphos complexes 23. The eight‐membered metallacycle adopts a relatively rigid boat‐like conformation, minimizing the steric interactions and likely stabilised by π‐stacking interactions between the aromatic rings bonded to both phosphorous atoms; the distance between the silver and iron atoms is 4.41 Å.…”

Section: Methodssupporting

confidence: 67%

“…This complex shows a P,P-bidentate coordination to silver, similar to that found in Pt II -Taniaphos complexes. [23] The eight-membered metallacycle adopts a relatively rigid boat-like conformation, minimizing the steric interactions and likely stabilised by p-stacking interactions between the aromatic rings bonded to both phosphorous atoms; the distance between the silver and iron atoms is 4.41 . Taking the structure of complex [AgOAc (3)] as starting point, the acetate anion was substituted by the model azomethine ylide with a coordination mode similar to that found in the previously studied most stable complex with Fesulphos (complex I).…”

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confidence: 99%

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Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of α‐Iminonitriles

Robles‐Machin

Alonso

Adrio

et al. 2010

Chemistry A European J

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Dedicated to Professor Josep M. Ribó on the occasion of his 70th birthdayThe 1,3-dipolar cycloaddition of azomethine ylides with alkenes is one of the most powerful and convergent methods for the stereoselective synthesis of pyrrolidines, [1] a heterocyclic moiety widely present in the structure of natural products, pharmaceuticals [2] and chiral ligands. [3] Improving the overall chemical and stereochemical efficiency of this reaction, pioneered by Grigg with stoichiometric metal chiral complexes, [4] a great effort has been devoted in recent years in the development of catalytic asymmetric protocols. In this field a wide variety of outstanding chiral complex catalysts have been reported, [5] mainly Ag I , [5f,g,j,m,q-s] Cu I[5e,h,i,k,l,o,t-w] and Cu II[5d] catalysts, but also Zn II , [5x] Ni II[5n] and Ca II[5p] complexes. In addition, several organocatalytic asymmetric methods have been also developed in the last few years. [6] Concerning the scope of the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides, although there is an ample tolerance with regard to the nature of the dipolarophile (i.e., a,b-unsaturated esters, maleimides, a,b-unsaturated nitriles, enones, enals, nitroalkenes, vinyl sulfones and fullerene), the structural variety at the azomethine dipole is much more limited. By far most catalytic asymmetric versions reported to date are based on the use of a-iminocarbonyl substrates, specifically a-iminoesters. The great effectiveness of a-iminoesters as dipole precursors relies on the enhanced acidity of the a-position and the formation of a robust five-membered, N,O-bidentate-metalated, azomethine ylide, which facilitates the asymmetric induction from the chiral ligand. The inherent limitation of this strategy is the restricted structural versatility with regard to the substitution at C2, always providing pyrrolidines with a C2 carboxylate ester substitution.To access other types of substituted pyrrolidines, a-iminonitrile precursors are very appealing, since in the resulting 2-cyanopyrrolidines [7] the cyano group could further act as leaving group allowing its formal substitution by hydrogen or by a carbon nucleophile, [8] and thus leading to a wider variety of substituted pyrrolidines. Two decades ago Kane-A C H T U N G T R E N N U N G masa, Tsuge et al. reported the non-enantioselective thermal [9] and LDA-promoted (LDA = lithium diisopropyl- A C H T U N G T R E N N U N G amide)[10] cycloaddition of alkyl-substituted a-iminonitriles with electron-deficient dipolarophiles, but the catalytic asymmetric version of this process remained to be developed. We describe herein the first catalytic asymmetric procedure for the 1,3-dipolar cycloaddition of a-iminonitriles, as well as some synthetic applications and a DFT theoretical study on the presumed nature of the metalated 1,3-dipole.To evaluate the viability of a-iminonitriles as dipole precursors in catalytic asymmetric 1,3-dipolar cycloadditions, we first studied the reaction of N-benzylidenaminoacetonitrile (1) with meth...

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Section: Methodssupporting

confidence: 67%

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confidence: 99%

Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of α‐Iminonitriles

Robles‐Machin

Alonso

Adrio

et al. 2010

Chemistry A European J

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“…With regard to the potential use of the ortho isomers of ( S p )‐ 3 , 5 , 8 as supporting ligands in Pd‐catalyzed reactions, the introduction of an additional phosphine moiety would change the binding properties from hemilabile, to bidentate . This would allow for a new access to such bis(phosphines), which are known to give a high ee within catalytic reactions .…”

Section: Resultsmentioning

confidence: 99%

Reactivity of Planar‐Chiral α‐Ferrocenyl Carbocations towards Electron‐Rich Aromatics

et al. 2019

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The reaction of the enantiopure, planar‐chiral α‐ferrocenyl carbocation (Sp)‐2‐(P(=S)Ph2)FcCH2+ (Fc = Fe(η5‐C5H5)(η5‐C5H3)) towards electron‐rich arenes C6H5E (E = NH2, NMe2, NiPr2, NPh2, PPh2, P(=S)Ph2, OH, SH, SMe) regarding either a nucleophilic attack of the group E or an electrophilic aromatic substitution reaction of the arene at the CH2+ unit is reported. It was found that the amino, oxo or thio functionalities gave the respective ferrocenes in various product distributions, while the P‐based species didn't. Appropriate thiophosphine derivatives could be reduced to their PIII species that were applied as supporting ligands in atropselective C,C cross‐coupling reactions for the synthesis of sterically hindered biaryls, where sandwich compound (Sp)‐1‐(PPh2)‐2‐(o‐NMe2‐C6H4)CH2‐Fc gave an ee of 69 % (1 mol‐% [Pd]), which is up to date the highest observed value for planar‐chiral ferrocenes. The absolute configuration of the chiral ferrocenes was confirmed by single‐crystal X‐ray diffraction analysis. For seleno phosphane 1‐(P(=Se)Ph2)‐2‐(CH2OH)‐Fc a unique Se single‐atom transfer occurred within its reaction with Sanger's reagent. The presence of two chemically different Se atoms in 1‐(P(=Se)Ph2)‐2‐(((2,4‐(NO2)2‐C6H3)Se)CH2)‐Fc was confirmed by 77Se{1H} NMR spectroscopy and single‐crystal X‐ray diffraction analysis, respectively.

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“…For the synthesis, coordination behaviour and use of Walphostype ligands in asymmetric catalysis, see: Weissensteiner et al (2002); Sturm et al (2003); Wang et al (2008). For crystal structures with Walphos-type ligands, see: Moberg et al (2007); Maddox et al (2008). For crystal structures of Ru(II)-(p-cymene) complexes with non-ferrocenyl phosphane ligands, see: Jensen et al (1998); Lalrempuia et al (2003); Chaplin & Dyson (2007).…”

Section: Related Literaturementioning

confidence: 99%

(R,R_Fc,S_Ru)-Chlorido(η⁶-p-cymene){1-[1-(diphenylphosphanyl)ethyl]-2-[2-(diphenylphosphanyl)phenyl]ferrocene-κ²P,P′}ruthenium(II) hexafluoridophosphate

2011

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Taniaphos and Walphos ligands: Oxidative electrochemistry and complexation. Synthesis, characterization, oxidative electrochemistry and X-ray structures of [(Taniaphos/Walphos)MCl2] (M=Pd or Pt)

Cited by 10 publications

References 47 publications

Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of α‐Iminonitriles

Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of α‐Iminonitriles

Reactivity of Planar‐Chiral α‐Ferrocenyl Carbocations towards Electron‐Rich Aromatics

(R,R_Fc,S_Ru)-Chlorido(η⁶-p-cymene){1-[1-(diphenylphosphanyl)ethyl]-2-[2-(diphenylphosphanyl)phenyl]ferrocene-κ²P,P′}ruthenium(II) hexafluoridophosphate

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Taniaphos and Walphos ligands: Oxidative electrochemistry and complexation. Synthesis, characterization, oxidative electrochemistry and X-ray structures of [(Taniaphos/Walphos)MCl2] (M=Pd or Pt)

Cited by 10 publications

References 47 publications

Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of α‐Iminonitriles

Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of α‐Iminonitriles

Reactivity of Planar‐Chiral α‐Ferrocenyl Carbocations towards Electron‐Rich Aromatics

(R,RFc,SRu)-Chlorido(η6-p-cymene){1-[1-(diphenylphosphanyl)ethyl]-2-[2-(diphenylphosphanyl)phenyl]ferrocene-κ2P,P′}ruthenium(II) hexafluoridophosphate

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(R,R_Fc,S_Ru)-Chlorido(η⁶-p-cymene){1-[1-(diphenylphosphanyl)ethyl]-2-[2-(diphenylphosphanyl)phenyl]ferrocene-κ²P,P′}ruthenium(II) hexafluoridophosphate