Mechanism of 8-Aminoquinoline Directed Ni-Catalyzed C(sp3)-H Functionalization: Paramagnetic Ni(II) Species, and the Deleterious Effect of Na2CO3 as a Base

10.26434/chemrxiv.13667807 ◽

2021 ◽

Author(s):

Junyang Liu ◽

Samuel Johnson

Keyword(s):

Carboxylic Acid ◽

Dft Calculations ◽

Resting State ◽

Deleterious Effect ◽

Oxidative Addition ◽

Catalytic Performance ◽

Low Energy ◽

Aryl Iodides ◽

Paramagnetic Complexes ◽

Carbonate Anion

Studies into the mechanism of 8-aminoquinoline-directed nickel-catalyzed C(sp3)–H arylation with iodoarenes are described, in an attempt to determine the catalyst resting state and optimize catalytic performance. Paramagnetic complexes are identified that are undergo the key C–H activation step. Hammett analysis using electronically different aryl iodides suggests a concerted oxidative addition mechanism for the C–H functionalization step; DFT calculations were also performed to support this finding. When Na2CO3 is used as the base the rate determination step for C–H functionalization appears to be 8-aminoquinoline deprotonation and binding to Ni. The carbonate anion was also observed to provide a deleterious NMR inactive low-energy off-cycle resting state in catalysis. Replacement of Na2CO3 with NaOtBu not only improved catalysis at milder conditions but also eliminated the need for carboxylic acid and phosphine additives.

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Mechanism of 8-Aminoquinoline Directed Ni-Catalyzed C(sp3)-H Functionalization: Paramagnetic Ni(II) Species, and the Deleterious Effect of Na2CO3 as a Base

10.26434/chemrxiv.13667807.v2 ◽

2021 ◽

Author(s):

Junyang Liu ◽

Samuel Johnson

Keyword(s):

Carboxylic Acid ◽

Dft Calculations ◽

Resting State ◽

Deleterious Effect ◽

Oxidative Addition ◽

Catalytic Performance ◽

Low Energy ◽

Aryl Iodides ◽

Paramagnetic Complexes ◽

Carbonate Anion

Studies into the mechanism of 8-aminoquinoline-directed nickel-catalyzed C(sp3)–H arylation with iodoarenes are described, in an attempt to determine the catalyst resting state and optimize catalytic performance. Paramagnetic complexes are identified that are undergo the key C–H activation step. Hammett analysis using electronically different aryl iodides suggests a concerted oxidative addition mechanism for the C–H functionalization step; DFT calculations were also performed to support this finding. When Na2CO3 is used as the base the rate determination step for C–H functionalization appears to be 8-aminoquinoline deprotonation and binding to Ni. The carbonate anion was also observed to provide a deleterious NMR inactive low-energy off-cycle resting state in catalysis. Replacement of Na2CO3 with NaOtBu not only improved catalysis at milder conditions but also eliminated the need for carboxylic acid and phosphine additives.

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Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

10.26434/chemrxiv.10321946.v1 ◽

2019 ◽

Author(s):

Alejandra Gomez-Torres ◽

J. Rolando Aguilar-Calderón ◽

Carlos Saucedo ◽

Aldo Jordan ◽

Alejandro J. Metta-Magaña ◽

...

Keyword(s):

Dft Calculations ◽

Ring Opening ◽

Thiophene Ring ◽

Oxidative Addition ◽

Reductive Elimination ◽

Thermally Induced ◽

Titanium Complex

The masked Ti(II) synthon (Ketguan)(η6-ImDippN)Ti (1) oxidatively adds across thiophene to give ring-opened (Ketguan)(ImDippN)Ti[κ2-S(CH)3CH] (2). Complex 2 is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate 1 – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from 2. Finally, pressurizing solutions of 2 with H2 (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (Ketguan)(ImDippN)Ti(S) (3) and butane.

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Three novel Cu(II), Cd(II) and Cr(III) complexes of 6−Methylpyridine−2−carboxylic acid with thiocyanate: Synthesis, crystal structures, DFT calculations, molecular docking and α-Glucosidase inhibition studies

Tetrahedron ◽

10.1016/j.tet.2018.10.054 ◽

2018 ◽

Vol 74 (50) ◽

pp. 7198-7208 ◽

Cited By ~ 20

Author(s):

Davut Avcı ◽

Sümeyye Altürk ◽

Fatih Sönmez ◽

Ömer Tamer ◽

Adil Başoğlu ◽

...

Keyword(s):

Molecular Docking ◽

Carboxylic Acid ◽

Dft Calculations ◽

Crystal Structures ◽

Inhibition Studies

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The role of hypervalent iodine(iii) reagents in promoting alkoxylation of unactivated C(sp3)–H bonds catalyzed by palladium(ii) complexes

Chemical Science ◽

10.1039/d1sc01230d ◽

2021 ◽

Author(s):

Payam Abdolalian ◽

Samaneh K. Tizhoush ◽

Kaveh Farshadfar ◽

Alireza Ariafard

Keyword(s):

Dft Calculations ◽

Oxidative Addition ◽

Hypervalent Iodine

This work uses DFT calculations to explore Pd(ii)-catalysed iodine(iii)-mediated alkoxylation of unactivated C(sp3)–H bonds and reveals how important the isomerization is in triggering the oxidative addition of ArIX2 to Pd(ii).

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Influence of Nd:YAG Laser Irradiation on an Adhesive Restorative Procedure

Operative Dentistry ◽

10.2341/05-110 ◽

2006 ◽

Vol 31 (5) ◽

pp. 604-609 ◽

Cited By ~ 17

Author(s):

M. Franke ◽

A. W. Taylor ◽

A. Lago ◽

M. C. Fredel

Keyword(s):

Statistical Analysis ◽

Bond Strength ◽

Laser Irradiation ◽

Significant Influence ◽

Nd:Yag Laser ◽

Deleterious Effect ◽

Adhesive System ◽

High Energy ◽

Low Energy ◽

Adhesive Penetration

Clinical Relevance Statistical analysis of the results obtained in this study shows that Nd:YAG laser irradiation on the adhesive system has a significant influence on bond strength to dentin. Bond strength is improved by better adhesive penetration when low energy is applied; whereas, high energy densities have a deleterious effect on the procedure.

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ChemInform Abstract: DICARBONYLRHODIUM(I) COMPLEXES OF POLYPYRROLE MACROCYCLES. PART 1. PREPARATION AND OXIDATIVE ADDITION REACTIONS WITH ALKYL HALIDES AND CARBOXYLIC ACID ANHYDRIDES

Chemischer Informationsdienst ◽

10.1002/chin.197713340 ◽

1977 ◽

Vol 8 (13) ◽

pp. no-no

Author(s):

A. M. ABEYSEKERA ◽

R. GRIGG ◽

J. TROCHA-GRIMSHAW ◽

V. VISWANATHA

Keyword(s):

Carboxylic Acid ◽

Oxidative Addition ◽

Alkyl Halides ◽

Addition Reactions ◽

Acid Anhydrides

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Palladium-Catalysed C–F Alumination of Fluorobenzenes: Mechanistic Diversity and Origin of Selectivity

10.26434/chemrxiv.12053601.v1 ◽

2020 ◽

Author(s):

Feriel Rekhroukh ◽

Wenyi Chen ◽

Ryan Brown ◽

Andrew J. P. White ◽

Mark Crimmin

Keyword(s):

Dft Calculations ◽

Bond Activation ◽

Oxidative Addition ◽

Fluorine Content ◽

Model Potential ◽

Heterometallic Complex ◽

Experimental Support ◽

Highly Active ◽

Reaction Proceeds ◽

Directing Group

A palladium pre-catalyst, [Pd(PCy3)2] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)2CH}Al] (1, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp2 C–F bonds to sp2 C–Al bonds and provides a route into reactive organoaluminium complexes (2a-h) from fluorocarbons. The catalyst is highly active. Reactions proceed within 5 minutes at 25 ºC (and at appreciable rates at even –50 ºC) and the scope includes low-fluorine-content substrates such as fluorobenzene, difluorobenzenes and trifluorobenzenes. The reaction proceeds with complete chemoselectivity (C–F vs C–H) and high regioselectivities ( >90% for C–F bonds adjacent to the most acidic C–H sites). The heterometallic complex [Pd(PCy3)(1)2] was shown to be catalytically competent. Catalytic C–F alumination proceeds with a KIE of 1.1–1.3. DFT calculations have been used to model potential mechanisms for C–F bond activation. These calculations suggest that two competing mechanisms may be in operation. Pathway 1 involves a ligand-assisted oxidative addition to [Pd(1)2] and leads directly to the product. Pathway 2 involves a stepwise C–H to C–F functionalisation mechanism in which the C–H bond is broken and reformed along the reaction coordinate, allowing it to act as a directing group for the adjacent C–F site. This second mechanism explains the experimentally observed regioselectivity. Experimental support for this C–H activation playing a key role in C–F alumination was obtained by employing [{(MesNCMe)2CH}AlH2] (3, Mes = 2,4,6-trimethylphenyl) as a reagent in place of 1. In this instance, the kinetic C–H alumination intermediate could be isolated. Under catalytic conditions this intermediate converts to the thermodynamic C–F alumination product.

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