Palladium‐Catalyzed C2−H Arylation of Unprotected (N−H)‐Indoles “On Water” Using Primary Diamantyl Phosphine Oxides as a Class of Primary Phosphine Oxide Ligands

Moncea, Oana; Poinsot, Didier; Fokin, Andrey A.; Schreiner, Peter R.; Hierso, Jean‐Cyrille

doi:10.1002/cctc.201800187

Cited by 29 publications

(14 citation statements)

References 58 publications

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“…Upon proton coupling, characteristic triplets are observed due to coupling of the phosphorus atoms to two directly bonded hydrogen atoms with a characteristic 1 JP,H coupling constant of 1 JP,H = 477.5 Hz in 1:Mes* (c.f. 9-hydroxydiamant-4-yl)P(H)2O; 1 JP,H = 448.4 Hz [38,39] ). The corresponding hydrogen atoms show a doublet signal with the same coupling constant at ca.…”

Section: Resultsmentioning

confidence: 99%

On the ambiphilic character of phosphanylidenephosphoranes and manipulation of phosphinidenoid reactivity with Lewis acids

Dankert

Fischer

Hering‐Junghans

2022

Preprint

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Phosphanylidenephosphoranes of the type R−P(PR’3), also known as phospha-Wittig reagents, can be utilized in a variety of bond activation reactions pursuing their phosphinidenoid reactivity. In here, we thoroughly show that a facile PMe3 for H2O exchange gives access to various primary phosphine oxides of the general formula RP(H)2O (R = Mes*, MesTer, DipTer). The molecular structure of DipTerP(H)2O was determined and provided the first picture of such species in the solid state. However, phosphanylidenephosphoranes are described to be highly nucleophilic as well. We show that the attachment of main group Lewis acids such as GaCl3 and GaI3 to2 R−P(PMe3) yielded highly sensitive, yet stable coordination compounds [RP(GaX3)PMe3] (R = Mes*, DipTer) or [(RPPMe3)2GaCl2]GaCl4 (R = MesTer). In contrast to the free phosphanylidenephosphoranes, these species reacted differently with H2O which was demonstrated for [(Mes*PPMe3)GaI3]. Here the formation of the phosphinophosphonium cation [Mes*P(H)PMe3]+ and different anions was observed with combined NMR spectroscopic and SC-XRD (SC-XRD = single crystal diffraction analysis) studies. This work demonstrates that the ambiphilic character of phosphanylidenephosphoranes can be utilized to manipulate the reactivity of R−P(PMe3) towards water, giving primary phosphine oxides, whereas the Lewis acid adducts [(RPPMe3)GaX3] gave phosphino-phosphonium species.

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Section: Resultsmentioning

confidence: 99%

On the ambiphilic character of phosphanylidenephosphoranes and manipulation of phosphinidenoid reactivity with Lewis acids

Dankert

Fischer

Hering‐Junghans

2022

Preprint

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“…Direct C–H functionalization of indoles is potentially of great synthetic utility, providing access to an important class of heterocyclic systems. − In fact, an indole scaffold is considered as a privileged structure in medicinal chemistry, and it is present in a large number of natural products endowed with biological activity. − …”

Section: Introductionmentioning

confidence: 99%

“…While catalytic methods for direct C2–H arylation of indoles have been widely explored, − to our knowledge, only a few reports have been disclosed on the use of heterogeneous Pd/C as a catalyst. − Among them, two papers are based on the use of diphenyliodonium tetrafluoroborate in EtOH or water, which allowed the arylation of indole or N -methylindole, respectively. High C2 selectivity has been achieved although the yields of isolated products are moderate. , …”

Section: Introductionmentioning

confidence: 99%

Polarclean/Water as a Safe and Recoverable Medium for Selective C2-Arylation of Indoles Catalyzed by Pd/C

Campana

Massaccesi

Santoro

et al. 2020

ACS Sustainable Chem. Eng.

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Herein, we report the use of nontoxic, water-miscible Polarclean as a safe dipolar aprotic solvent for the metal-catalyzed direct C2–H arylation of indoles using Pd/C as a catalyst. The developed method allows reaching excellent yields and regioselectivities, and it tolerates various substituents on both indole and diaryliodonium salt scaffolds. Polarclean is fully recoverable and reusable; it shows a very low leaching of the metal catalyst, allowing its complete recovery and reuse for at least six representative reaction runs.

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“…On the other hand, Sanford and Larrosa separately demonstrated phosphine ligand-free regioselective C-2 arylation of indoles in the presence of an acid, the chemistry introduced by Gaunt, under much milder conditions. Inspired by these works, several other groups developed protocols for C-2 arylation, − in particular, on heterogeneous supports or in green media . However, every protocol has its own scopes and limitations, which indulge researchers to develop new and contemporary methods.…”

Section: Introductionmentioning

confidence: 99%

Mechanochemical Pd(II)-Catalyzed Direct and C-2-Selective Arylation of Indoles

et al. 2019

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A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed using Pd(II) as the catalyst in the absence of phosphine ligands in a ball-mill. The developed protocol is highly C-2 selective and tolerant of structural variations with electron-rich and electron-deficient substituents both in indoles and iodoarenes. Arylation is possible in both unprotected indoles and Nprotected indoles with the electron-donating group with the former substrate being relatively slower to react and little less yielding. Indoles with a deactivated five-membered ring could also take part in the reaction with ease. The scalability of the reaction was demonstrated by conducting the reaction in the gram scale. In general, the reactions were achieved in a shorter time than the conventional methods.

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Palladium‐Catalyzed C2−H Arylation of Unprotected (N−H)‐Indoles “On Water” Using Primary Diamantyl Phosphine Oxides as a Class of Primary Phosphine Oxide Ligands

Cited by 29 publications

References 58 publications

On the ambiphilic character of phosphanylidenephosphoranes and manipulation of phosphinidenoid reactivity with Lewis acids

On the ambiphilic character of phosphanylidenephosphoranes and manipulation of phosphinidenoid reactivity with Lewis acids

Polarclean/Water as a Safe and Recoverable Medium for Selective C2-Arylation of Indoles Catalyzed by Pd/C

Mechanochemical Pd(II)-Catalyzed Direct and C-2-Selective Arylation of Indoles

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