Catalytic Stereoselective Semihydrogenation of Alkynes to <i>E</i>‐Alkenes

Michaelides, Iacovos N.; Dixon, Darren J.

doi:10.1002/anie.201208120

Cited by 52 publications

(30 citation statements)

References 26 publications

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“…The olefin insertion into a MH bond is a key step in the catalytic cycles proposed for olefin functionalization reactions and leads to the formation of alkyl metal intermediates . The acetylene insertion into the MH bond also plays an important role in a number of catalytic processes, such as hydrogenation or polymerization reaction, which receives considerable attention due to its utility in organic syntheses . However, the addition of 1 equiv of alkynes into several polyhydride complexes leads to the displacement of H 2 from the metal center, rather than the insertion into the MH bond, unless the alkenes or alkynes contain strong electron‐withdrawing groups, such as CO 2 Me, CO 2 t Bu, CO 2 TMS, and so on .…”

Section: Introductionmentioning

confidence: 99%

“…[7,8] The acetylene insertion into the M H bond also plays an important role in a number of catalytic processes, such as hydrogenation or polymerization reaction, which receives considerable attention due to its utility in organic syntheses. [9][10][11] However, the addition of 1 equiv of alkynes into several polyhydride complexes leads to the displacement of H 2 from the metal center, rather than the insertion into the M H bond, unless the alkenes or alkynes contain strong electron-withdrawing groups, such as CO 2 Me, CO 2 t Bu, CO 2 TMS, and so on. [12][13][14][15] Komine and coworkers also reported the insertion of selective alkenes into inert M H bonds of molybdenum and tungsten hydrides MHCp(CO) 3 (M Mo, W) catalyzed by palladium(0) complexes, and showed that (Z)-and (E)-alkenes (MeO 2 CC CCO 2 Me) can be easily inserted into the Mo/W H bonds and have a high reaction rate and yield.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO₂Me) by Cp₂TaH₃

Wang

Zheng

et al. 2019

J Comput Chem

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The elementometalation process is a fundamental chemical step in several catalytic cycles. In this work, density functional theory computations have elucidated the detailed elementometalation mechanism of activated alkyne RCCR(RCO2Me) by Cp2TaH3 and rationalized the selectivity in experimental findings. The calculated results show that in the formation process of (E)‐olefin monohydride((E)‐Pro), the Gibbs free energy barrier is low and the entire reaction is spontaneous and exothermic; thus, (E)‐Pro can be formed easily. The formation of (Z)‐η2‐olefin monohydride complex ((Z)‐Pro) is difficult due to its high Gibbs free energy barrier. The formation process (E)‐Pro consists of the following five steps: hydride H1‐shift, conformational isomerism 1, hydride H2‐shift, conformational isomerism 2, and olefin coordination process. Topological analysis shows that there is a five‐membered ring plane structure in the reaction pathway and that the final product (E)‐Pro belongs to a typical η2‐olefin monohydride complex. Our calculated results provide an explanation for experimental observations and useful insights for further development of olefin functionalization. © 2019 Wiley Periodicals, Inc.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO₂Me) by Cp₂TaH₃

Wang

Zheng

et al. 2019

J Comput Chem

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“…[3] We reasoned that semihydrogenation of alkynes would be both ac hallenging and meaningful playground for aromatic palladium clusters. [4] Whereas these reactions are wells tudied in homogenous catalysis, [5] no catalytic methodf or the semireductiono fa lkynes has been reportedb yu sing discrete Pd clusters,a nd examples with other clusters are rare. [6] (Z)-Alkenes can be formed in high yields by using electron-rich Pd 0 complexes bearing suitable N-heterocyclic carbenes or chelating diphosphinesa sl igands.…”

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confidence: 99%

“…This was surprising, as the two clusters have nearly identicals tructural and electronic features [3] and low-valent Pt complexes can be efficient reduction catalysts (for ap ossible rationalization see below). [4] We next examined av ast array of aromatic alkynes ( Table 2). Increasingt he length of the aliphatic arm demandedalonger reactiont ime to reach full conversion ( Table 2, entries 3a nd 4).…”

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Catalytic Semireduction of Internal Alkynes with All‐Metal Aromatic Complexes

et al. 2015

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DedicatedtoProfessor Iwao Ojima on the occasiono fhis 70th birthday As imple catalytic method involving all-metal aromatic frameworks as precatalysts ensures an efficient route to (Z)-alkenes. Aromatic triangular palladium clusters wereu sed to reduce internal alkynesw ithout any trace of the formation of alkane side products. These trinuclear complexes provide ac atalytic system that parallels the activity and selectivity of their best mononuclear peers, and the catalyst likely operates through complementary mechanisms.All-metal aromaticsa re cyclic molecules that present delocalized molecular orbitals similart ot hose of regular aromatics but involve metal atoms in their cores.[1] They can therefore display ag reater variety of bondingm odes and represent an ideal bridge that connects discrete homogeneous complexes with heterogeneous metallic nanoparticles thanks to their delocalized metal-metal bonding.[2] We wanted to gain somei nsight into the consequences of metal aromaticity by studying the catalytic behavior of stable and easily accessible triangular d-orbital-aromatic palladium clusters. [3] We reasoned that semihydrogenation of alkynes would be both ac hallenging and meaningful playground for aromatic palladium clusters.[4] Whereas these reactions are wells tudied in homogenous catalysis, [5] no catalytic methodf or the semireductiono fa lkynes has been reportedb yu sing discrete Pd clusters,a nd examples with other clusters are rare.[6] (Z)-Alkenes can be formed in high yields by using electron-rich Pd 0 complexes bearing suitable N-heterocyclic carbenes or chelating diphosphinesa sl igands. [7] Their efficiency represents ap robing test and therefore at ool to check the potential of metal aromatics. [8] Trinuclear metal-aromatic complexes are interesting platforms for catalytic applications( Scheme 1). Featuring noncoordinating counteranions, the positive charge of these clusters shouldp rovide them with Lewis acid character.A tt he same time, their delocalized HOMO might grant Lewis basic properties to the triangularc ore. Their resonance-enhanced stabilization should increaset heir robustness. From ap ractical point of view,t hese complexes are definitely stable to oxygen and moisture, are formed in highy ields from commercial reagents in one-pot,and feature easily tunable organic fragments. [3] We report the application of am etal-aromatic framework in ac atalytic reaction. Triangular Pd 3 clusters were used to efficiently reduce internal alkynes to (Z)-alkenesu nder transfer-hydrogenation conditions, completely excluding over-reduction to alkanes and preserving other reducible groups, even in the presence of al arge excess amount of the donor.We used 1-phenylpropyne (1a)a sam odel substrate. Its internalt riple bond is conjugated with the aromatic ring, which makesi tt he candidate of choice to evaluatec atalyst efficiency (Table 1). In at ypical experiment, 1a (0.3 mmol) was stirred with aP d 3 catalyst (1 mol %) and triethylammonium formate (5 equiv.) in THF.T he mixture was heatedt or eflux, an...

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“…Considering the fact that high E-stereoselective semireduction of a triple bond is an important goal of contemporary organic chemistry [7][8][9][10][11][12][13][14] , herein, we wish to report the development of such a highly selective copper(I)-catalysed tandem three-component coupling-semireduction reaction of commercially readily available terminal alkynes, aldehydes and 3-pyrroline or isoindoline affording N-allyl amines with an E-C ¼ C bond (Fig. 1b).…”

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confidence: 99%

Unexpected E-stereoselective reductive A3-coupling reaction of terminal alkynes with aldehydes and amines

Yuan

2014

Nat Commun

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The transition-metal catalysed three-component coupling of an alkyne, an aldehyde and an amine has been became a widely used method for preparing propargylic amines. Here, we report an unexpected copper(I)-catalysed E-stereoselective reduction of propargylic amines in situ formed from readily available terminal alkynes, aldehydes and 3-pyrroline or isoindoline via [1,5]-hydride transfer, affording E-allylic amines. Through mechanistic studies, it is believed that the unsaturated cyclic dialkylamine is acting as hydrogen donor.

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Catalytic Stereoselective Semihydrogenation of Alkynes to E‐Alkenes

Cited by 52 publications

References 26 publications

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO₂Me) by Cp₂TaH₃

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO₂Me) by Cp₂TaH₃

Catalytic Semireduction of Internal Alkynes with All‐Metal Aromatic Complexes

Unexpected E-stereoselective reductive A3-coupling reaction of terminal alkynes with aldehydes and amines

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Catalytic Stereoselective Semihydrogenation of Alkynes to E‐Alkenes

Cited by 52 publications

References 26 publications

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO2Me) by Cp2TaH3

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO2Me) by Cp2TaH3

Catalytic Semireduction of Internal Alkynes with All‐Metal Aromatic Complexes

Unexpected E-stereoselective reductive A3-coupling reaction of terminal alkynes with aldehydes and amines

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Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO₂Me) by Cp₂TaH₃

Mechanism and Stereoselectivity of the Elementometalation Process of Activated Alkyne RCCR(RCO₂Me) by Cp₂TaH₃