Design of Benzimidazolyl Phosphines Bearing AlterableP,OorP,N-Coordination: Synthesis, Characterization, and Insights into Their Reactivity

Wong, Siu Wai; Choy, Pui Ying; Zhao, Qingyang; Yuen, On Ying; Yeung, Chung Chiu; So, Chau Ming; Kwong, Fuk Yee

doi:10.1021/acs.organomet.0c00816

Cited by 10 publications

(5 citation statements)

References 45 publications

(16 reference statements)

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“…A series of P,O-type indolylphosphine ligands ( Amidole-Phos ) was synthesized using a simple one-pot protocol from indole, acid chlorides, and aryl/alkylchlorophosphines (Scheme A) . Notably, the indole skeleton can be replaced by benzimidazole to afford an alterable P,O- or P,N-coordinated monophosphorus ligands (Scheme B) . These catalyst systems were found to be orthogonal in the Pd-catalyzed SMC (Scheme C) and amination of aryl chlorides (Scheme D).…”

Section: Other Related Heterocyclic Monophosphorus Ligandsmentioning

confidence: 99%

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Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

2022

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Conspectus This Account presents an overview of a promising collection of phosphine ligands simply made from the modular Fischer indolization process and their applications in modern arylation processes. Using one easily accessible 2-arylindole scaffold, three major phosphino-moiety-positioned ligand series can be readily generated. We have attempted to explore challenging electrophilic and nucleophilic partners for the coupling reaction using the modular ligand tool. For the electrophilic partner study, CM-phos-type ligands, where the phosphino group is located at the 2-arene position of 2-arylindole, allow the successful cross-coupling of aryl mesylates. The CM-phos ligand forms a palladacycle before entering the cross-coupling catalytic cycle. For the nucleophilic partner investigation, the indole C3-positioned phosphines show the first accomplishment of Pd-catalyzed organotitanium nucleophile arylation. Indeed, the aryl-titanium nucleophile undergoes cross-coupling more efficiently than does the organoboron coupling partner in particular cases. Moreover, in the indole C3-positioned phosphine series, the −PPh2-containing ligands perform better in the highly sterically hindered cross-coupling of aryl chlorides than do ligands containing the −PCy2 moiety. The catalyst loading can even be reduced to 0.2 mol % Pd for tetra-ortho-substituted biaryl synthesis. This finding offers a new perspective on the next-generation design of phosphine ligands in which the sterically bulky and electron-rich −PR2 group (R = alkyl) may not be necessary for the cross-coupling of aryl chlorides. In general, we hypothesize that a good balance of steric and electronic properties for entertaining the oxidative addition and reductive elimination steps is crucial to the success of the reaction. For the steric factor, the highly sterically congested −PR2 group normally favors the reductive elimination, yet we conjecture that this sterically bulky group would serve as an obstacle for the incoming aryl halides. For the electronic factor, the electron rich −PR2 group is believed to support the oxidative cleavage of the C(Ar)–Cl bond by donating more electron density to the corresponding σ* orbital. Nevertheless, the high electron richness of the −PR2 group may disfavor the reductive elimination electronically. Overall, an appropriate balance of both electron density and steric bulkiness is suggested to allow the sterically hindered cross-coupling to proceed smoothly. We have found that the −PPh2-containing ligand is a good starting point for this investigation. The formation of aromatic carbon–carbon (C–C) and carbon–heteroatom (C–X) bonds from aryl chlorides was successfully realized using our proprietary phosphines. In addition to the indole-core-bearing ligand skeleton, we also explored the relevant imidazolyl and carbazolyl phosphines for their unique applications. Interestingly, the carbazolyl ligand, having more flexible C–N axial chirality, displays particular interchangeable Pd–N and Pd–arene coordination, which facilitates both oxid...

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Section: Other Related Heterocyclic Monophosphorus Ligandsmentioning

confidence: 99%

“…56 Notably, the indole skeleton can be replaced by benzimidazole to afford an alterable P,O-or P,N-coordinated monophosphorus ligands (Scheme 18B). 57 These catalyst systems were found to be orthogonal in the Pd-catalyzed SMC (Scheme 18C) and amination of aryl chlorides (Scheme 18D).…”

Section: C2-indolyl/benzimidazolyl-based Monophosphorus Ligandsmentioning

confidence: 99%

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

2022

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“…6,5‐Bicyclic ring systems such as an indolyl [20a–e,30] or benzimidazolyl [21a,b,d,31] monophosphines have found applications in cross‐coupling reactions. To the best of our knowledge, no one has investigated the catalytic activity of cross‐coupling reactions based on imidazopyridines as heterocyclic ligand types.…”

Section: Introductionmentioning

confidence: 99%

Suzuki‐Miyaura and Buchwald‐Hartwig Cross‐Coupling Reactions Utilizing a Set of Complementary Imidazopyridine Monophosphine Ligands

Jacoby,

Harris,

Wiemann

et al. 2024

ChemistrySelect

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Palladium‐catalyzed Suzuki‐Miyaura and Buchwald‐Hartwig cross‐coupling reactions have become indispensable tools in the synthesis of otherwise inaccessible compounds because of the efficient, catalytic nature of these styles of reactions. The development of novel monophosphine ligands to achieve the cross‐coupling of substrates that are generally unreactive under standard conditions has developed into an extremely important area of research in the field of organometallic chemistry. Herein, we show the use of an imidazopyridine monophosphine ligand JagPhos I in the Suzuki‐Miyaura palladium‐catalyzed cross‐coupling reaction to deliver sterically‐hindered biaryls and unsymmetrical biheterocycles. We also report the scope and limitations of imidazopyridine monophosphine ligand JagPhos II in the Buchwald‐Hartwig amination reactions of (hetero)aryl halides with anilines, secondary amines, and primary amines.

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“…[2] Hemilabile oxygen ligands have been synthesized using a variety of functional groups such as acetal, sulfonyl, amido, ether, sulfinamido, and phosphine oxide. [3] In this study, we synthesized a new hemilabile P,O-type ligand, N-disulfonyl bicyclic bridgehead phosphorus triamide, by combining Nsulfonyl and bicyclic bridgehead phosphorus (Figure 1a). The new ligand was employed to uncover a novel applica-tion in the Pd-catalyzed hydrosilylation of unactivated alkenes and conjugated dienes through the use of tertiary silanes (Figures 1b and c).…”

Section: Introductionmentioning

confidence: 99%

Palladium‐Catalyzed Hydrosilylation of Unactivated Alkenes and Conjugated Dienes with Tertiary Silanes Controlled by Hemilabile Hybrid P,O Ligand

2023

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Novel P,O‐type ligands, N‐disulfonyl bicyclic bridgehead phosphorus triamides, were synthesized and utilized in Pd‐catalyzed hydrosilylation involving tertiary silanes, unactivated alkenes, and conjugated dienes. The ligand displayed a remarkable level of reactivity for alkene hydrosilylation with tertiary silanes and its use resulted in a significant improvement in the regioselectivity of diene hydrosilylation towards 1,2‐hydrosilylation. X‐ray crystallographic analysis confirmed the bidentate nature of the ligand, with coordination of phosphorus and oxygen. Control experiments provided evidence for the formation of Pd0 species and the reversibility of Pd−H insertion in the reaction mechanism. Density functional theory (DFT) computations supported the importance of the hemilabile P,O ligand in stabilizing both the rate‐determining transition state of Pd−H insertion and the transition state of reductive elimination that determines the regioselectivity.

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Design of Benzimidazolyl Phosphines Bearing AlterableP,OorP,N-Coordination: Synthesis, Characterization, and Insights into Their Reactivity

Cited by 10 publications

References 45 publications

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

Facile Assembly of Modular-Type Phosphines for Tackling Modern Arylation Processes

Suzuki‐Miyaura and Buchwald‐Hartwig Cross‐Coupling Reactions Utilizing a Set of Complementary Imidazopyridine Monophosphine Ligands

Palladium‐Catalyzed Hydrosilylation of Unactivated Alkenes and Conjugated Dienes with Tertiary Silanes Controlled by Hemilabile Hybrid P,O Ligand

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