Catalyst Deactivation During Rhodium Complex‐Catalyzed Propargylic C−H Activation

Möller, Saskia; Jannsen, Nora; Rüger, Julia; Drexler, Hans‐Joachim; Horstmann, Moritz; Bauer, Felix; Breit, Bernhard; Heller, Detlef

doi:10.1002/chem.202102219

Cited by 3 publications

(3 citation statements)

References 39 publications

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“…Before reaction monitoring experiments were conducted, the reaction conditions were optimized. The isolated precatalyst [Rh(μ-Cl)(DPEPhos)] 2 1 was used instead of the in situ system ([Rh(μ-Cl](COD)] 2 /DPEPhos) to ensure full conversion to the precatalyst and to exclude negative influences of the free diolefin on the catalysis. , It was found that the order of the addition of the substrates has a significant influence on the organometallic species formed during the reaction. If the allene is added first, a high concentration of the above-mentioned Rh(III) rhodacycle 5 was detected, which could be circumvented by first adding BTAH (Figure S15).…”

Section: Resultsmentioning

confidence: 99%

The Mechanism of Rh(I)-Catalyzed Coupling of Benzotriazoles and Allenes Revisited: Substrate Inhibition, Proton Shuttling, and the Role of Cationic vs Neutral Species

Jannsen,

Reiß,

Drexler

et al. 2024

J. Am. Chem. Soc.

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Direct coupling of benzotriazole to unsaturated substrates such as allenes represents an atom-efficient method for the construction of biologically and pharmaceutically interesting functional structures. In this work, the mechanism of the N 2selective Rh complex-catalyzed coupling of benzotriazoles to allenes was investigated in depth using a combination of experimental and theoretical techniques. Substrate coordination, inhibition, and catalyst deactivation was probed in reactions of the neutral and cationic catalyst precursors [Rh(μ-Cl)(DPEPhos)] 2 and [Rh(DPEPhos)(MeOH) 2 ] + with benzotriazole and allene, giving coordination, or coupling of the substrates. Formation of a rhodacycle, formed by unprecedented 1,2-coupling of allenes, is responsible for catalyst deactivation. Experimental and computational data suggest that cationic species, formed either by abstraction of the chloride ligand or used directly, are relevant for catalysis. Isomerization of benzotriazole and cleavage of its N−H bond are suggested to occur by counteranion-assisted proton shuttling. This contrasts with a previously proposed scenario in which oxidative N−H addition at Rh is one of the key steps. Based on the mechanistic analysis, the catalytic coupling reaction could be optimized, leading to lower reaction temperature and shorter reaction times compared to the literature.

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Section: Resultsmentioning

confidence: 99%

The Mechanism of Rh(I)-Catalyzed Coupling of Benzotriazoles and Allenes Revisited: Substrate Inhibition, Proton Shuttling, and the Role of Cationic vs Neutral Species

Jannsen,

Reiß,

Drexler

et al. 2024

J. Am. Chem. Soc.

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“…Experimental observation of such phenomena is of course limited given the rapid dimer-monomer equilibrium resulting often in identical NMR chemical shifts; however, techniques such as DOSY NMR and kinetic determinations complement the computational studies. 10,36 Experimental findings on the mechanism of formation of Rh-3…”

Section: Dalton Transactions Papermentioning

confidence: 99%

Unexpected alkyl isomerization at the silicon ligand of an unsaturated Rh complex: combined experiment and theory

Abeynayake,

Le,

Sanchez-Lecuona

et al. 2023

Dalton Trans.

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“…In accordance to the proposed mechanisms for the rhodium catalyzed addition of pronucleophiles to allenes and alkynes, , in particular the catalyzed cyclization of allenyl sulfonylcarbamates, a mechanism for the rhodium catalyzed diastereoselective cyclization of tosylureas has been devised (Scheme ). For syn -selective conditions, electron-deficient carboxylic acids were shown to increase yield and selectivity and may help to generate the active rhodium-hydride intermediate A by formation of a suitable precatalyst as was recently described by Heller and Breit .…”

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Stereodivergent Palladium- and Rhodium-Catalyzed Intramolecular Addition of Tosylureas to Allenes: Diastereoselective Synthesis of Tetrahydropyrimidinones

2021

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The intramolecular addition of tosylureas to allenes is highly syn-/anti-diastereoselective when employing a palladium or rhodium-based catalytic system and affords 1,3-cyclic ureas. Under palladium catalysis a range of thermodynamic anti-tetrahydropyrimidinones are accessible, while rhodium catalysis allows synthesis of the kinetic syn-tetrahydropyrimidinones. For a representative scope of substrates both cyclic ureas were obtained in excellent yields and diastereoselectivities. The obtained tetrahydropyrimidinones were shown to be easily deprotected and modified to demonstrate the synthetic value.

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Catalyst Deactivation During Rhodium Complex‐Catalyzed Propargylic C−H Activation

Abstract: This paper is dedicated to Professor Barry Trost for the outstanding importance of his work in the field of homogeneous catalysis.

Cited by 3 publications

References 39 publications

The Mechanism of Rh(I)-Catalyzed Coupling of Benzotriazoles and Allenes Revisited: Substrate Inhibition, Proton Shuttling, and the Role of Cationic vs Neutral Species

The Mechanism of Rh(I)-Catalyzed Coupling of Benzotriazoles and Allenes Revisited: Substrate Inhibition, Proton Shuttling, and the Role of Cationic vs Neutral Species

Unexpected alkyl isomerization at the silicon ligand of an unsaturated Rh complex: combined experiment and theory

Stereodivergent Palladium- and Rhodium-Catalyzed Intramolecular Addition of Tosylureas to Allenes: Diastereoselective Synthesis of Tetrahydropyrimidinones

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