Regioselective Allene Hydrosilylation Catalyzed by <i>N</i>-Heterocyclic Carbene Complexes of Nickel and Palladium

Miller, Zachary D.; Li, Wei; Belderraín, Tomás R.; Montgomery, John

doi:10.1021/ja407749w

Cited by 107 publications

(64 citation statements)

References 51 publications

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“…On the other hand, scenarios where directing groups are not easily installed or removed present a different set of challenges and require the development of non-directed approaches. 1,6-10 In these cases involving non-directed additions, π-components in regioselective and regiodivergent processes can typically be classified as biased or unbiased as illustrated for alkenes, alkynes, and allenes (Scheme 2). With biased substrates such as monosubstituted π-systems 1a-c , or alternatively disubstituted π-systems 2a-c where R 1 and R 2 markedly differ in steric or electronic properties, structural features of the substrates influence the properties of the π-system.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Basis for Regioselection and Regiodivergence in Nickel-Catalyzed Reductive Couplings

et al. 2015

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CONSPECTUS The control of regiochemistry is a considerable challenge in the development of a wide array of catalytic processes. Simple π-components such as alkenes, alkynes, 1,3-dienes, and allenes are among the many classes of substrates that present complexities in regioselective catalysis. Considering an internal alkyne as a representative example, when steric and electronic differences between the two substituents are minimal, differentiating among the two termini of the alkyne presents a great challenge. In cases where the differences between the alkyne substituents are substantial, overcoming those biases to access the regioisomer opposite that favored by substrate biases often presents an even greater challenge. Nickel-catalyzed reductive couplings of unsymmetrical π-components make up a group of reactions where control of regiochemistry presents a challenging but important objective. In the course of our studies of aldehyde-alkyne reductive couplings, complementary solutions to challenges in regiocontrol have been developed. Through careful selection of the ligand and reductant, as well as the more subtle reaction variables such as temperature and concentration, effective protocols have been established that allow highly selective access to either regiosiomer of the the allylic alcohol products using a wide range of unsymmetrical alkynes. Computational studies and an evaluation of reaction kinetics have provided an understanding of the origin of the regioselectivity control. Throughout the various procedures described, the development of ligand-substrate interactions play a key role, and the overall kinetic descriptions were found to differ between protocols. Rational alteration of the rate-determining step plays a key role in the regiochemistry reversal strategy, and in one instance, the two possible regioisomeric outcomes in a single reaction were found to operate by different kinetic descriptions. With this mechanistic information in hand, the empirical factors that influence regiochemistry can be readily understood, and more importantly, the insights suggest simple and predictable experimental variables to achieving a desired reaction outcome. These studies thus present a detailed picture of the influences that control regioselectivity in a specific catalytic reaction, but they also delineate strategies for regiocontrol that may extend to numerous classes of reactions. The work provides an illustration of how insights into the kinetics and mechanism of a catalytic process can rationalize subtle empirical findings and suggest simple and rational modifications in procedure to access a desirable reaction outcome. Furthermore, these studies present an illustration of how important challenges in organic synthesis can be met by novel reactivity afforded by base metal catalysis. The use of nickel catalysis in this instance not only provides an inexpensive and sustainable method for catalysis, but also enables unique reactivity patterns not accessible to other metals.

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Section: Introductionmentioning

confidence: 99%

Mechanistic Basis for Regioselection and Regiodivergence in Nickel-Catalyzed Reductive Couplings

et al. 2015

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“…Montgomery and co‐workers reported that vinylsilanes could be accessed with Pd(0) NHC catalysts (Figure , L1 ) . They also established the classic N‐heterocyclic carbene complexes of Pd(0) catalyst system (Figure , L2 ) for branched allylsilanes. Another method for branched allylsilanes was developed by Schmidt et al.…”

Section: Figurementioning

confidence: 95%

“…Hence, the development of new and efficient methods for the synthesis of versatile allylsilanes has been paid more and more attention. The hydrosilylation of allenes is one of the most straightforward and atom‐economical approaches to prepare such compound, which has been achieved with various metal catalysts, such as Mo, Co, Ni, Pd and Au . However, controling the regio‐ and stereoselectivity is still challenging in this reaction, as up to six potential isomeric products can be generated (Figure a).…”

Section: Figurementioning

confidence: 99%

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A Bithiophene‐Promoted ppm Levels of Palladium‐Catalyzed Regioselective Hydrosilylation of Terminal Allenes

et al. 2020

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A bithiophene−alkyne‐based compound was synthesized and first utilized as a ligand for the selective hydrosilylation of allenes with primary and secondary phenylsilanes. It shows high selectivity towards the production of branched allylsilanes with a wide range of allenes. It is worth mentioning that the catalytic loading of the palladium can be reduced to 500 ppm. This work opens a new front of using bidentate thiophene ligand as a reaction promoter in transition‐metal‐catalyzed organic reaction.

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“…Montgomery and co‐workers reported the regioselective hydrosilylation of allenes catalyzed by Ni 0 and Pd 0 catalysts in the presence of an NHC ligand (Scheme ). Interestingly, vinylsilanes are the major products when a Ni catalyst is used in the presence of a bulky NHC ligand, whereas allylsilanes are the major products by using Pd catalysts in the presence of small NHC ligands.…”

Section: Ni‐catalyzed Hydrofunctionalization (H−x)mentioning

confidence: 99%

Computational Insights into the Reaction Mechanisms of Nickel‐Catalyzed Hydrofunctionalizations and Nickel‐Dependent Enzymes

Zhang

Chung

2018

Asian J Org Chem

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For several decades, transition-metal catalysis has been ap opular methodf or many functional group transformations in organicc hemistry.R ecent developments in sustainability and applicationso fe arth-abundant metals have resulted in as ynthetic renaissance and have attracted considerable interest in less toxic and inexpensive first-row transition-metal catalysts such as nickel. Herein, we highlight some recent computationali nsights into the reactionm ech-anismso fN i-catalyzed hydrofunctionalizations (i.e.,h ydrogenation,h ydrovinylation, hydroacylation, hydroheteroarylation, hydrosilylation, and hydroalkoxylation) and Ni-dependent enzymes (i.e.,l actater acemase, methyl-CoM reductase, and [NiFe]-hydrogenase). These computational studies provide insightsi nto these reactionm echanisms and thus assist in the developmentand design of sustainable catalysts.Scheme3.Ni-catalyzed asymmetric hydrogenationofb-amino nitroolefins (TFE = 2,2,2-trifluoroethanol, TON = turnover number).Scheme4.Computedf avorable catalytic cycle for the Ni-catalyzed asymmetric hydrogenation in the presence of the (S)-binapine ligand. Relative Gibbs free energy valuesare shown.Scheme5.Computedf ree energies of proposed key catalyticcycle for the Ni-catalyzed hydrogenation in the presence of ad imeric Ni speciesa nd the (S)-binapine ligand (only the key transition states were computed).Scheme6.[Si II (Xant)Si II ]Ni(h 2 -1,3-cod)-catalyzedolefin hydrogenation.Scheme20. The proposed proton-coupled electron transfer mechanism for lactate racemization (see Ref.[35]). Scheme21. (a) Methane formation reaction catalyzed by MCR and (b) the active-site structure of F 430 .Scheme22. Different proposed mechanisms for methanef ormation catalyzed by MCR (see Ref. [49]).

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Regioselective Allene Hydrosilylation Catalyzed by N-Heterocyclic Carbene Complexes of Nickel and Palladium

Cited by 107 publications

References 51 publications

Mechanistic Basis for Regioselection and Regiodivergence in Nickel-Catalyzed Reductive Couplings

Mechanistic Basis for Regioselection and Regiodivergence in Nickel-Catalyzed Reductive Couplings

A Bithiophene‐Promoted ppm Levels of Palladium‐Catalyzed Regioselective Hydrosilylation of Terminal Allenes

Computational Insights into the Reaction Mechanisms of Nickel‐Catalyzed Hydrofunctionalizations and Nickel‐Dependent Enzymes

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