Formation of C–C bonds via ruthenium-catalyzed transfer hydrogenation

Moran, Joseph; Krische, Michael J.

doi:10.1351/pac-con-11-10-18

Cited by 111 publications

(32 citation statements)

References 81 publications

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“…In this aspect, elegant examples have recently been reported. [19][20][21][22] Scheme 2 differentiates Krische's ''C-H functionalization'' from the ''BH'' substitution of alcohols by N-nucleophiles. This review only summarizes the progress in ''BH'' substitution of alcohols by N-nucleophiles under homogeneous organometallic for the synthesis of various biologically active materials.…”

Section: Qingfu Wangmentioning

confidence: 99%

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

2015

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Transition metal-catalyzed substitution of alcohols by N-nucleophiles (or N-alkylation of amines and related compounds with alcohols) avoids the use of alkylating agents by means of borrowing hydrogen (BH) activation of the alcohol substrates. Water is produced as the only by-product, which makes the "BH" processes atom-economic and environmentally benign. Diverse types of homogeneous organometallic and heterogeneous transition metal catalysts, and substrates such as N-nucleophiles including amines, amides, sulfonamides and ammonia, and various alcohols, can be used for this purpose, demonstrating the promising potential of "BH" processes to replace the procedures using traditional alkylating agents in pharmaceutical and chemical industries. Borrowing hydrogen activation of alcohols for C-N bond formation has recently been paid more and more attention, and a lot of new and novel procedures and examples have been documented. This critical review summarizes the recent advances in "BH" substitution of alcohols by N-nucleophiles since 2009. "Semi-BH" N-alkylation processes with or without an external hydrogen acceptor are also briefly presented. Suitable discussion of the "BH" strategy provides new principles for establishing green processes to replace the relevant traditional synthetic methods for C-N bond formation.

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Section: Qingfu Wangmentioning

confidence: 99%

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

2015

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“…Recent advances in C–H activations with Ir, Pd, , and Rh catalysts have led to many efficient C–H functionalization strategies. C–H activation reactions with ruthenium complexes are relatively less developed, although ruthenium catalysts have exhibited great reactivity and stability in many important catalytic processes such as olefin metathesis, hydrogenation, and transfer hydrogenation reactions. Interestingly, although only a few examples of Ru-mediated C(sp 3 )–H activation reactions have been reported; , these processes may take place via several distinct mechanistic pathways (Figure ) including a two-step mechanism involving C–H oxidative addition followed by reductive elimination, σ-bond metathesis of an agostic complex (σ-complex assisted metathesis, or σ-CAM), a base-induced electrophilic C–H activation, or a carboxylate-assisted concerted metalation–deprotonation (CMD) mechanism. ,, …”

Section: Introductionmentioning

confidence: 99%

Intramolecular C–H Activation Reactions of Ru(NHC) Complexes Combined with H₂ Transfer to Alkenes: A Theoretical Elucidation of Mechanisms and Effects of Ligands on Reactivities

2017

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Recent experimental studies have identified Ru(II) NHC complexes that are highly reactive in the tandem intramolecular C(sp 3 )−H activation of an N-alkyl substituent to form a metallacycle and transfer hydrogenation of alkenes. These complexes are promising candidates for tandem catalytic processes that depend on a reversible uptake of hydrogen ("borrowing hydrogen catalysis"). We have elucidated the reaction mechanisms by density functional theory calculations and investigated ligand effects on reactivity. The reaction of ruthenium dihydride complex [Ru-(H) 2 (NHC)(CO)(PPh 3 ) 2 ] (1) with ethylene occurs via dissociative ligand exchange to replace one of the phosphine ligands with ethylene, followed by hydride migration and reductive elimination to form a Ru(0) intermediate. Subsequent C−H activation occurs via an oxidative addition mechanism. Bulkier NHC and phosphine ligands facilitate the dissociation of phosphine, which leads to a lower overall barrier. In addition, the N-i Pr substituted NHC ligand promotes the C−H oxidative addition/ruthenacyclization due to the release of steric strain caused by the N-i Pr group and the substituents on the NHC backbone. The reaction with the monohydride monochloride complex [RuHCl(NHC)(PPh 3 ) 2 ] (2) occurs via ligand exchange and hydride migration to form an alkyl ruthenium(II) complex. The type of phosphine ligand determines whether the subsequent intramolecular C−H activation proceeds via an associative or a dissociative mechanism. In the associative pathway, C−H activation occurs via a concerted σ-bond metathesis mechanism, which directly transfers the hydrogen atom from the C−H bond of the N-alkyl group on the NHC to the alkyl ligand on ruthenium. In the dissociative pathway, C−H activation occurs via stepwise C−H oxidative addition to form a Ru(IV) intermediate followed by reductive elimination of the alkane product.

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“…25,26 As documented in this account, ruthenium catalyzed transfer hydrogenation now serves as the basis for C-C bond constructions that directly convert lower alcohols to higher alcohols. [16][17][18][19][20] This body of work was preceded by studies on metal catalyzed carbonyl reductive couplings mediated by elemental hydrogen, as initially described in 2002 by the present author, 27 and as documented in the review literature. 28,29 …”

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confidence: 90%

“…14,15 The purpose of this review is to provide a comprehensive summary of ruthenium catalyzed C-C couplings induced via alcohol-mediated transfer hydrogenation. [16][17][18][19][20] These studies build on several important milestones in the area of ruthenium catalyzed hydrogenation and transfer hydrogenation (Scheme 1). In 1971, one decade beyond the seminal work of Halpern on ruthenium catalyzed hydrogenation, 6 transfer hydrogenations employing ruthenium catalysts were described.…”

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confidence: 99%

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

Perez

Oda

Geary

et al. 2016

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Formation of C–C bonds via ruthenium-catalyzed transfer hydrogenation

Cited by 111 publications

References 81 publications

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

Intramolecular C–H Activation Reactions of Ru(NHC) Complexes Combined with H₂ Transfer to Alkenes: A Theoretical Elucidation of Mechanisms and Effects of Ligands on Reactivities

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

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Formation of C–C bonds via ruthenium-catalyzed transfer hydrogenation

Cited by 111 publications

References 81 publications

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

Intramolecular C–H Activation Reactions of Ru(NHC) Complexes Combined with H2 Transfer to Alkenes: A Theoretical Elucidation of Mechanisms and Effects of Ligands on Reactivities

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

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Intramolecular C–H Activation Reactions of Ru(NHC) Complexes Combined with H₂ Transfer to Alkenes: A Theoretical Elucidation of Mechanisms and Effects of Ligands on Reactivities