Buchwald–Hartwig amination using Pd(<scp>i</scp>) dimer precatalysts supported by biaryl phosphine ligands

Kirlikovali, Kent O.; Cho, Eunho; Downard, Tyler J.; Grigoryan, L. A.; Han, Zheng; Hong, Sooji; Jung, Dahee; Quintana, Jason C.; Reynoso, Vanessa; Ro, Sooihk; Shen, Yi; Swartz, Kevin; Sahakyan, Elizabeth Ter; Wixtrom, Alex I.; Yoshida, Brandon; Rheingold, Arnold L.; Spokoyny, Alexander M.

doi:10.1039/c8dt00119g

Cited by 21 publications

(15 citation statements)

References 43 publications

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“…Those two complexes are not assigned as Pd 0 complexes because they did not react with para ‐fluoro iodobenzene (10 equiv). As recently reported, the dimeric [Pd I (XPhos)] 2 [BF 4 ] 2 exhibited two 31 P{ 1 H} NMR doublets at 39.26 (d, J PP =84 Hz) and 23.15 ppm (d, J PP =84 Hz) in CD 2 Cl 2 because of a complexation of the Pd atom with the 2,4,6‐triisopropylphenyl group, which makes the two phosphines non‐equivalent. Since acetate ions are released from Pd(OAc) 2 in the reduction process, this cationic Pd I –Pd I dimer might not be formed.…”

Section: Resultsmentioning

confidence: 79%

Formation of XPhos‐Ligated Palladium(0) Complexes and Reactivity in Oxidative Additions

Wagschal

Perego

Simon

et al. 2019

Chemistry A European J

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Understanding the nature of the intermediate species operating within a palladium catalytic cycle is crucial for developing efficient cross‐coupling reactions. Even though the XPhos/Pd(OAc)2 catalytic system has found numerous applications, the nature of the active catalytic species remains elusive. A Pd0 complex ligated to XPhos has been detected and characterized in situ for the first time using cyclic voltammetry and NMR techniques. In the presence of XPhos, Pd(OAc)2 initially associates with the ligand to form a complex in solution, which has been characterized as PdII(OAc)2(XPhos). This PdII center is then reduced to the Pd0(XPhos)2 species by an intramolecular process. This study also sheds light on the formation of PdI–PdI dimers. Finally, a kinetic study probes a dissociative mechanism for the oxidative addition with aryl halides involving Pd0(XPhos) as the reactive species in equilibrium with the unreactive Pd0(XPhos)2. Remarkably, the reportedly poorly reactive PhCl reacts at room temperature in the oxidative addition, which confirms the crucial role of the XPhos ligand in the activation of aryl chlorides.

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Section: Resultsmentioning

confidence: 79%

Formation of XPhos‐Ligated Palladium(0) Complexes and Reactivity in Oxidative Additions

Wagschal

Perego

Simon

et al. 2019

Chemistry A European J

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“…The high temperature is thought to be necessary to allow disproportionation of the stable Pd(I) dimer. A series of analogues of this complex was prepared by an alternate route starting from [(MeCN) 6 Pd 2 ](BF 4 ) 2 ( 9 ) and the desired 2‐biphenylphosphine (Scheme ) . The RuPhos analogue of 8 was an effective precatalyst for the amination of aryl chlorides, but as with 8 , required relatively high temperatures.…”

Section: Palladium Precatalystsmentioning

confidence: 99%

Development of Palladium Precatalysts that Efficiently Generate LPd(0) Active Species

Shaughnessy

2019

Israel Journal of Chemistry

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Palladium catalysts have become central to modern organic synthesis, particularly in the context of crosscoupling reactions to form CÀ C and C-heteroatom bonds. The development of highly efficient catalyst systems has seen a transition from the use of in situ-generated catalysts derived from a ligand source and palladium precursor to the use of preformed palladium-ligand complexes that can efficiently generate the active species. The design of these systems has focused on optimizing the generation of the LPd(0) species presumed to be the active catalysts with most state-of-the-art ligand systems. This review will highlight the development of Pd(0), Pd(I), and Pd(II) precatalysts that efficiently generate LPd(0) active species with a focus on their activation mechanisms and applications in catalysis. Scheme 3. Synthesis of diene-stabilized LPd(0).Scheme 4. COD-stabilized LPd(0) and application to fluorination reactions. Scheme 14. Activation routes for Pd(allyl) precatalysts. Scheme 15. Competition between formation of active species and inactive μ-allyl palladium(I) dimers.

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“…Pd(I) dimers have been exploited as pre-catalysts in a range of catalytic reactions, including Suzuki coupling, the Heck reaction, Kumada coupling, Negishi coupling and Buchwald Hartwig amination. [20][21][22][23][24][25][26][27] Accordingly, we briefly examined the amination of 4-bromotoluene with morpholine, under conditions reported recently using complex 6 as a pre-catalyst 27 and the results are summarised in Scheme 3. As can be seen, complex 4a is a viable pre-catalyst for the reaction, rather than a decomposition product, giving similar performance to a 1:1 mixture of palladium acetate and SPhos.…”

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confidence: 99%

The surprisingly facile formation of Pd(i)–phosphido complexes from ortho-biphenylphosphines and palladium acetate

et al. 2019

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Buchwald–Hartwig amination using Pd(i) dimer precatalysts supported by biaryl phosphine ligands

Cited by 21 publications

References 43 publications

Formation of XPhos‐Ligated Palladium(0) Complexes and Reactivity in Oxidative Additions

Formation of XPhos‐Ligated Palladium(0) Complexes and Reactivity in Oxidative Additions

Development of Palladium Precatalysts that Efficiently Generate LPd(0) Active Species

The surprisingly facile formation of Pd(i)–phosphido complexes from ortho-biphenylphosphines and palladium acetate

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