First enantiopure phosphapalladacycle with a palladium bonded stereogenic carbon as the sole chirality source

Dunina, V. V.; Gorunova, O. N.; Ливанцов, М. В.; Grishin, Yuri K.; Кочетков, К. А.; Churakov, Andrei V.; Кузьмина, Л. Г.

doi:10.1016/j.poly.2010.09.024

Cited by 7 publications

(3 citation statements)

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“…154), and the point group of the palladium(II) dimer is C 2 with the 2-fold axis passing through the μ-chloro ligand and bisecting the Pd(1)–Cl(2)–Pd(1′) plane. The Pd–P and Pd–C bond lengths in 3 [Pd(1)–P(1) = 2.199(2) Å; Pd(1)–C(18) = 2.100(7) Å] are consistent with those found in the related P,C-chelate complexes (i.e., [1,2-C 6 H 4 (PR 2 )(CH 2 )PdL 2 ]: R = t -Bu, Pd–P = 2.238(2) Å, Pd–C = 2.078(7) Å; R = o -tolyl, Pd–P = 2.266(2) Å, Pd–C = 2.079(7) Å; R = o -tolyl, Pd–P = 2.2325(9) Å, and Pd–C = 2.053(3) Å] . Importantly, the angle at C(12) is consistent with sp 2 hybridization and its formulation as the iminium carbon, [C–C–N = 120.3(6)°], and the carbon–nitrogen bond length [1.29(1) Å] is consistent with other iminium compounds. , The 1 H– 1 H COSY NMR spectrum shows a weak interaction between the N–H proton (δ = 7.69) and the proton of the adjacent carbon (δ = 3.88).…”

Section: Resultssupporting

confidence: 68%

“…The binding of phosphine 4 to palladium(II) affords iv, in which the o-CH 2 group (formerly of Mes) is susceptible to Pd-insertion and formal loss of HCl to afford iminium species v. Similar proton abstractions from the o-Me substituent have been observed for Pd(II) or Pt(II) complexes of o-tolylsubstituted and related phosphines. 16,22 The final step involves the loss of cod from v and dimerization to the final product 3. As mentioned previously, dinuclear complex 3 has very low solubility in CH 2 Cl 2 and precipitates directly from the reaction mixture.…”

Section: ■ Introductionmentioning

confidence: 99%

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Reaction of an Enantiomerically Pure Phosphaalkene-Oxazoline with MeM Nucleophiles (M = Li and MgBr): Stereoselectivity and Noninnocence of the P-Mesityl Substituent

et al. 2014

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The addition of alkyl nucleophiles (MeM, M = Li, MgBr) across the PC bond of an enantiomerically pure phosphaalkene-oxazoline followed by protonation of the C anion affords phosphines with three chirality centers. The formation of palladium(II) complexes of the resultant phosphines permitted structural characterization of the products by X-ray diffraction. The choice of nucleophile has a profound effect on the product distributions. For instance, the Grignard reagent adds in a diastereoselective manner to give one major phosphine product with P-and C-stereocenters. In contrast, addition of methyllithium has proven not only to be less stereoselective but also affords a fascinating cyclic phosphine product. Both the Grignard and RLi reactions involve proton transfer from the o-Me of the P-Mes substituent even though the products are quite different in each case. ■ INTRODUCTIONPhosphaalkene chemistry strikingly parallels that of its structural relatives, the alkenes and imines, in diverse areas ranging from ligand development for transition metals to functional groups in polymer science. 1 Increasingly, researchers are developing sophisticated compounds containing PC bonds that display unique properties, bonding, reactivity, and catalytic activity. 2 To this end, we have disclosed the synthesis and catalytic utility of enantiomerically pure phosphaalkenes of general structure A, a phosphaalkene-oxazoline hybrid (PhAkOx) (Chart 1). 3−5 PhAk-Ox complements existing acyclic (B and C) and cyclic (D and E) structural motifs that incorporate PC bonds within an enantiomerically enriched organic framework. 6Building on our work on the polymerization of MesPCPh 2 (Scheme 1), 7−9 we have successfully incorporated an enantiomerically pure phosphaalkene-oxazoline (PhAk-Ox, 1) into copolymers with styrene using radical methods of initiation. 5 Given that the anionic polymerizations of MesP CPh 2 can be living, thereby providing access to block copolymers with controlled architectures, 9 the possible extension of this methodology to the chiral PhAk-Ox monomer is intriguing. One can envisage stereoselective polymerizations of 1 that afford fascinating main chain chiral (or helical) polymers that possess novel physical properties and potential applications in asymmetric catalysis or in chiral separations. Thus far, homopolymers of PhAk-Ox (1) have not been

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Section: Resultssupporting

confidence: 68%

Section: ■ Introductionmentioning

confidence: 99%

Reaction of an Enantiomerically Pure Phosphaalkene-Oxazoline with MeM Nucleophiles (M = Li and MgBr): Stereoselectivity and Noninnocence of the P-Mesityl Substituent

et al. 2014

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“…The palladacycle has a constrained P–Pd–C angle (82.7°, 82.8°). This value is similar to that of the other reported five-membered ring palladacycles derived from alkylphosphines . Due to the steric strain, the P–C–C angles of the neopentyl groups are large (123.8–125.0°).…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Study of the Role of Substrate Steric Effects and Aniline Inhibition on the Bis(trineopentylphosphine)palladium(0)-Catalyzed Arylation of Aniline Derivatives

Gerlach

et al. 2017

ACS Catal.

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T h e m e c h a n i s m o f t h e b i s -(trineopentylphosphine)palladium(0) (Pd(PNp 3 ) 2 )-catalyzed coupling of aryl halides and aniline derivatives was studied in an effort to understand the role of substrate steric effects on the reaction. Prior studies had shown that the rate of Pd/ PNp 3 -catalyzed coupling of aryl bromides and aniline derivatives was largely unaffected by substrate steric demand. The oxidative addition of aryl bromides to Pd(PNp 3 ) 2 is found to follow first-order kinetics with a rate that is independent of both ligand and aryl halide concentration. Thus, the rate limiting step for oxidative addition of aryl bromides is irreversible ligand dissociation. In the case of aryl chlorides, the oxidative addition rate has a first-order dependence on [ArCl] and an inverse dependence on [PNp 3 ], indicating a mechanism involving reversible dissociation of the ligand followed by rate limiting oxidative addition. This difference in aryl halide effect was also found for the catalytic coupling reaction. Aryl bromide steric demand does not affect the coupling rate with hindered anilines, whereas the coupling rate of aryl chlorides is negatively affected by substrate steric demand. These results suggest that oxidative addition is rate limiting in the catalytic reaction for aryl chlorides but that oxidative addition is not rate limiting for aryl bromides. Aniline was found to give coupling rates significantly slower than those of 2,6-diisopropylaniline for both aryl bromides and chlorides. Aniline promotes the decomposition of the [(PNp 3 )Pd(Ar)(μ-X)] 2 catalytic intermediate to a catalytically inactive palladacycle ([(κ 2 -P,C-Np 2 PCH 2 C(Me 2 )CH 2 )Pd(μ-X)] 2 ) through C−H activation of a neopentyl group and elimination of arene. These studies show that the ability of the Pd/PNp 3 catalyst system to tolerate steric demand in aryl bromides stems from the fact that the rate limiting step of the catalytic cycle is independent of the concentration and steric demand of aryl bromides. A catalyst deactivation pathway involving ligand metalation was identified that is promoted by unhindered aniline derivatives.

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Cyclopalladated complexes containing an (sp3)C–Pd bond

Dickmu

Smoliakova

2020

Coordination Chemistry Reviews

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First enantiopure phosphapalladacycle with a palladium bonded stereogenic carbon as the sole chirality source

Cited by 7 publications

References 34 publications

Reaction of an Enantiomerically Pure Phosphaalkene-Oxazoline with MeM Nucleophiles (M = Li and MgBr): Stereoselectivity and Noninnocence of the P-Mesityl Substituent

Reaction of an Enantiomerically Pure Phosphaalkene-Oxazoline with MeM Nucleophiles (M = Li and MgBr): Stereoselectivity and Noninnocence of the P-Mesityl Substituent

Mechanistic Study of the Role of Substrate Steric Effects and Aniline Inhibition on the Bis(trineopentylphosphine)palladium(0)-Catalyzed Arylation of Aniline Derivatives

Cyclopalladated complexes containing an (sp3)C–Pd bond

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