scholarly journals Rh-catalyzed decarbonylation of conjugated ynones via carbon–alkyne bond activation: reaction scope and mechanistic exploration via DFT calculations

2015 ◽  
Vol 6 (5) ◽  
pp. 3201-3210 ◽  
Author(s):  
Alpay Dermenci ◽  
Rachel E. Whittaker ◽  
Yang Gao ◽  
Faben A. Cruz ◽  
Zhi-Xiang Yu ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Activation Reaction

We report a catalytic C–C bond activation of unstrained conjugated monoynonesviadecarbonylation to synthesize disubstituted alkynes.

ChemInform Abstract: Rh-Catalyzed Decarbonylation of Conjugated Ynones via Carbon-Alkyne Bond Activation: Reaction Scope and Mechanistic Exploration via DFT Calculations.

ChemInform ◽  
2015 ◽  
Vol 46 (34) ◽  
pp. no-no
Author(s):  
Alpay Dermenci ◽  
Rachel E. Whittaker ◽  
Yang Gao ◽  
Faben A. Cruz ◽  
Zhi-Xiang Yu ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Activation Reaction

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

Cu-catalyzed C–H Activation Reaction: One Pot Direct Synthesis of Xanthine and Uric Acid Derivatives from 5-Bromo Uracil

Synlett ◽  
2021 ◽  
Author(s):  
Habibur Rahaman ◽  
Brindaban Roy ◽  
Somjit Hazra ◽  
Biplab Mondal
Keyword(s):  
Uric Acid ◽  
Bond Activation ◽  
Direct Synthesis ◽  
One Pot ◽  
Activation Reaction

Abstract: A one pot direct synthesis of xanthine and uric acid derivates is reported. This simple yet efficient methodology illustrates concurrent formation of two C-N bonds using CuBr2 as catalyst and one of those C-N bonds is formed by uracil C6-H bond activation.

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

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(PCy<sub>3</sub>)<sub>2</sub>] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)<sub>2</sub>CH}Al] (<b>1</b>, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp<sup>2</sup> C–F bonds to sp<sup>2</sup> C–Al bonds and provides a route into reactive organoaluminium complexes (<b>2a-h</b>) 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(PCy<sub>3</sub>)(<b>1</b>)<sub>2</sub>] 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(<b>1</b>)<sub>2</sub>] 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)<sub>2</sub>CH}AlH<sub>2</sub>] (<b>3</b>, 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.

scholarly journals Heterolytic bond activation at gold: evidence for gold(iii) H–B, H–Si complexes, H–H and H–C cleavage

2019 ◽  
Vol 10 (9) ◽  
pp. 2633-2642 ◽  
Author(s):  
Luca Rocchigiani ◽  
Peter H. M. Budzelaar ◽  
Manfred Bochmann
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Bond Cleavage

Gold(iii) forms spectroscopically detectable H–B and H–Si σ-complexes; experiments and DFT calculations demonstrate heterolytic H–Si, H–H and H–C bond cleavage.

scholarly journals Femtosecond Infrared Studies of Chemical Bond Activation

1999 ◽  
Vol 19 (1-4) ◽  
pp. 253-262 ◽  
Author(s):  
M. C. Asplund ◽  
H. Yang ◽  
K. T. Kotz ◽  
S. E. Bromberg ◽  
M. J. Wilkens ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Chemical Bond ◽  
Bond Activation ◽  
Product Formation ◽  
Organometallic Complexes ◽  
Activation Time ◽  
Activation Reaction ◽  
Infrared Studies ◽  
Important Intermediate ◽  
Solvent Complex

The identification of the intermediates observed in bond activation reactions involving organometallic complexes on time scales from femtoseconds to milliseconds has been accomplished through the use of ultrafast infrared spectroscopy. C—H bond activation by the molecule Tp*Rh(CO)2 showed a final activation time of 200 ns in cyclic solvents, indicating a reaction barrier of 8.3 kcal/mol. An important intermediate is the partially dechelated η2-Tp*Rh(CO)(S) solvent complex, which was formed 200 ps after the initial photoexcitation. Si—H bond activation by CpM(CO)3 (M=Mn, Re) showed some product formation in less than 5 ps, indicating that the Si—H activation reaction is barrierless. The activated product was formed on several timescales, from picoseconds to nanoseconds, suggesting that there are different pathways for forming final product which are partitioned by the initial photoexcitation.

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