scholarly journals Pd(quinox)-catalyzed allylic relay Suzuki reactions of secondary homostyrenyl tosylates via alkene-assisted oxidative addition

2014 ◽  
Vol 5 (6) ◽  
pp. 2336-2339 ◽  
Author(s):  
Benjamin J. Stokes ◽  
Amanda J. Bischoff ◽  
Matthew S. Sigman
Keyword(s):  
Oxidative Addition ◽  
Cross Coupling ◽  
Mechanistic Studies ◽  
Suzuki Reactions

Pd(quinox)-catalyzed relay Suzuki reactions of secondary homostyrenyl tosylates are highly selective for allylic cross-coupling products. Mechanistic studies suggest that alkene precoordination enables a chelation-controlled oxidative addition.

scholarly journals Tandem C–O and C–H Activation at Palladium Enables Catalytic Direct C–H Alkenylation with Enol Pivalates

2021 ◽  
Author(s):  
Nahiane Pipaon Fernandez ◽  
Gregory Gaube ◽  
Kyla Woelk ◽  
Mathias Burns ◽  
David Leitch
Keyword(s):  
Bond Activation ◽  
Bond Formation ◽  
Palladium Catalysis ◽  
Oxidative Addition ◽  
Cross Coupling ◽  
Addition Product ◽  
Pivalic Acid ◽  
Mechanistic Studies ◽  
Limiting Step ◽  
Strong Bond Activation

The use of oxygen-based electrophiles in cross-coupling remains challenging for substrates with strong C–O bonds, with few examples that can combine C–O activation with an-other strong-bond activation in tandem. We report the first example of a direct, tandem C–O/C–H activation approach to C–C bond formation using palladium catalysis. This reaction combines C–O oxidative addition at enol pivalates with con-certed metallation deprotonation of functionalized heterocycles to achieve base-free direct C–H alkenylation, with pivalic acid as the only byproduct. Mechanistic studies reveal that the Pd(II) C–O oxidative addition product is the major catalyst resting state, indicating that C–H activation is the turnover-limiting step.

scholarly journals Nickel-catalyzed reductive coupling of homoenolates and their higher homologues with unactivated alkyl bromides

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Tingzhi Lin ◽  
Yuanyun Gu ◽  
Pengcheng Qian ◽  
Haixing Guan ◽  
Patrick J. Walsh ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transition Metal ◽  
Functional Groups ◽  
Oxidative Addition ◽  
Cross Coupling ◽  
Single Electron Transfer ◽  
Reductive Coupling ◽  
Mechanistic Studies ◽  
Alkyl Bromide ◽  
Alkyl Bromides

Abstract The catalytic generation of homoenolates and their higher homologues has been a long-standing challenge. Like the generation of transition metal enolates, which have been used to great affect in synthesis and medicinal chemistries, homoenolates and their higher homologues have much potential, albeit largely unrealized. Herein, a nickel-catalyzed generation of homoenolates, and their higher homologues, via decarbonylation of readily available cyclic anhydrides has been developed. The utility of nickel-bound homoenolates and their higher homologues is demonstrated by cross-coupling with unactivated alkyl bromides, generating a diverse array of aliphatic acids. A broad range of functional groups is tolerated. Preliminary mechanistic studies demonstrate that: (1) oxidative addition of anhydrides by the catalyst is faster than oxidative addition of alkyl bromides; (2) nickel bound metallocycles are involved in this transformation and (3) the catalyst undergoes a single electron transfer (SET) process with the alkyl bromide.

scholarly journals Mechanistic Studies of the Oxidative Addition of Aryl Halides to Ni(0) Centers Bearing Phosphine Ligands

2020 ◽  
Vol 74 (6) ◽  
pp. 495-498
Author(s):  
Pablo Marcelo Pérez-García ◽  
Marc-Etienne Moret
Keyword(s):  
Significant Influence ◽  
Oxidative Addition ◽  
Cross Coupling ◽  
Phosphine Ligands ◽  
Aryl Halides ◽  
Entry Point ◽  
Mechanistic Studies ◽  
Recent Advances ◽  
Mechanistic Understanding ◽  
Catalytic Cycles

The oxidative addition of aryl halides is a common entry point in catalytic cycles for cross-coupling and related reactions. In the case of phosphine-supported nickel(0) fragments, the formation of reactive Ni(ii)–aryl products often competes with the production of Ni(i) species. Here, recent advances in the mechanistic understanding of these reactions are highlighted. In particular, the denticity of the supporting ligand has a significant influence on the outcome of the reaction.

Ni(0)-Catalyzed α-Allylic Alkylation of Regular Ketones with 1,3-Dienes under pH and Redox-neutral Conditions

2019 ◽  
Author(s):  
Tiantian Chen ◽  
Yang Yang ◽  
Liyu Xie ◽  
Haijian Yang ◽  
Guangbin Dong ◽  
...  
Keyword(s):  
Oxidative Addition ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Dual Role ◽  
Allylic Alkylation ◽  
Cross Coupling Reaction ◽  
Neutral Conditions

<p>We report a Ni(0)-catalyzed cross coupling reaction between simple ketones and 1,3-dienes. A variety of a-allylic alkylation products were formed in an 1,2-addition manner with excellent regioselectivity. Water was found to significantly accelerate this transformation. A HO-Ni-H species generated from oxidative addition of Ni(0) to H<sub>2</sub>O is proposed to play a “dual role” in activating both the ketone and the diene substrate.</p>

Design and Development of Fe-Catalyzed Intra- and Intermolecular Carbofunctionalization of Vinyl Cyclopropanes

2019 ◽  
Author(s):  
Lei Liu ◽  
Wes Lee ◽  
Mingbin Yuan ◽  
Chris Acha ◽  
Michael B. Geherty ◽  
...  
Keyword(s):  
Bond Formation ◽  
Cross Coupling ◽  
Alkyl Halides ◽  
Grignard Reagents ◽  
Mechanistic Studies ◽  
Radical Intermediates ◽  
Design And Implementation ◽  
Solvent Cage ◽  
Radical Cascade ◽  
Radical Processes

Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. Mechanistic studies support the diffusion of the alkyl radical intermediates out of the solvent cage to participate in an intra- or -intermolecular radical cascade with the VCP followed by re-entering the Fe radical cross-coupling cycle to undergo selective C(sp2)-C(sp3) bond formation. Overall, we provide new design principles for Fe-mediated radical processes and underscore the potential of using combined computations and experiments to accelerate the development of challenging transformations.

scholarly journals Heterobiaryl synthesis by contractive C–C coupling via P(V) intermediates

Science ◽  
2018 ◽  
Vol 362 (6416) ◽  
pp. 799-804 ◽  
Author(s):  
Michael C. Hilton ◽  
Xuan Zhang ◽  
Benjamin T. Boyle ◽  
Juan V. Alegre-Requena ◽  
Robert S. Paton ◽  
...  
Keyword(s):  
Cross Coupling ◽  
The Other ◽  
Coupling Reactions ◽  
Mechanistic Studies ◽  
Alternative Approach ◽  
Metal Catalyzed ◽  
Polar Functional Groups ◽  
Pharmacological Function ◽  
Complex Drug ◽  
Acidic Alcohol

Heterobiaryls composed of pyridine and diazine rings are key components of pharmaceuticals and are often central to pharmacological function. We present an alternative approach to metal-catalyzed cross-coupling to make heterobiaryls using contractive phosphorus C–C couplings, also termed phosphorus ligand coupling reactions. The process starts by regioselective phosphorus substitution of the C–H bonds para to nitrogen in two successive heterocycles; ligand coupling is then triggered via acidic alcohol solutions to form the heterobiaryl bond. Mechanistic studies imply that ligand coupling is an asynchronous process involving migration of one heterocycle to the ipso position of the other around a central pentacoordinate P(V) atom. The strategy can be applied to complex drug-like molecules containing multiple reactive sites and polar functional groups, and also enables convergent coupling of drug fragments and late-stage heteroarylation of pharmaceuticals.

scholarly journals Controlling Non-Native B12 Reactivity and Catalysis in the Transcription Factor CarH

2021 ◽  
Author(s):  
Xinhang Yang ◽  
Benjamin H. R. Gerroll ◽  
Yuhua Jiang ◽  
Amardeep Kumar ◽  
Yasmine S. Zubi ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Vitamin B12 ◽  
Transcription Regulation ◽  
Bond Cleavage ◽  
Oxidative Addition ◽  
Mechanistic Studies ◽  
Organic Transformations ◽  
Carbon Bond ◽  
Wide Range ◽  
Hydride Elimination

Vitamin B12 derivatives catalyze a wide range of organic transformations, but B12-dependent enzymes are underutilized in biocatalysis relative to other metalloenzymes. In this study, we engineered a variant of the transcription factor CarH, called CarH*, that catalyzes styrene C-H alkylation with improved yield and selectivity relative to B12 itself. While the native function of CarH involves transcription regulation via AdoCbl Co(III)-carbon bond cleavage and β-hydride elimination to generate 4’,5’-didehydroadenosine, CarH*-catalyzed styrene alkylation proceeds via non-native oxidative addition and olefin addition coupled with a native-like β-hydride elimination. Mechanistic studies on this reaction echo findings from earlier studies on AdoCbl homolysis under strong cage conditions to suggest that CarH* can enable non-native radical chemistry with improved selectivity relative to B12 itself. These findings lay the groundwork for the development of B12-dependent enzymes as catalysts for a wide range of non-native transformations.

scholarly journals Mechanistic Studies of the Palladium-Catalyzed Desulfinative Cross-Coupling of Aryl Bromides and (Hetero)Aryl Sulfinate Salts

2020 ◽  
Vol 142 (7) ◽  
pp. 3564-3576 ◽  
Author(s):  
Antoine de Gombert ◽  
Alasdair I. McKay ◽  
Christopher J. Davis ◽  
Katherine M. Wheelhouse ◽  
Michael C. Willis
Keyword(s):  
Cross Coupling ◽  
Mechanistic Studies ◽  
Aryl Bromides ◽  
Palladium Catalyzed
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