scholarly journals Development of highly efficient platinum catalysts for hydroalkoxylation and hydroamination of unactivated alkenes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yali Zhou ◽  
Xingjun Xu ◽  
Hongwei Sun ◽  
Guanyu Tao ◽  
Xiao-Yong Chang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Rational Design ◽  
Platinum Catalysts ◽  
High Reactivity ◽  
Structural Components ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Naturally Occurring ◽  
Donor Acceptor ◽  
Type Intermediate

AbstractHydrofunctionalization, the direct addition of an X–H (e.g., X=O, N) bond across an alkene, is a desirable strategy to make heterocycles that are important structural components of naturally occurring molecules. Described here is the design and discovery of “donor–acceptor”-type platinum catalysts that are highly effective in both hydroalkoxylation and hydroamination of unactivated alkenes over a broad range of substrates under mild conditions. A number of alkene substitution patterns are accommodated, including tri-substituted, 1,1-disubstituted, (E)-disubstituted, (Z)-disubstituted and even mono-substituted double bonds. Detailed mechanistic investigations suggest a plausible pathway that includes an unexpected dissociation/re-association of the electron-deficient ligand to form an alkene-bound “donor–acceptor”-type intermediate. These mechanistic studies help understand the origins of the high reactivity exhibited by the catalytic system, and provide a foundation for the rational design of chiral catalysts towards asymmetric hydrofunctionalization reactions.

scholarly journals Development of Highly Efficient Platinum Catalysts for Hydroalkoxylation and Hydroamination of Unactivated Alkene

2020 ◽  
Author(s):  
Yali Zhou ◽  
Xingjun Xu ◽  
Hongwei Sun ◽  
Guanyu Tao ◽  
Xiaoyong Chang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Rational Design ◽  
Platinum Catalysts ◽  
High Reactivity ◽  
Structural Components ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Naturally Occurring ◽  
Donor Acceptor ◽  
Type Intermediate

Abstract Hydrofunctionalization, the direct additon of an X–H (e.g., X = O, N) bond across an alkene, is a desirable strategy to make heterocycles that are important structural components of naturally occurring molecules. Described here is the design and discovery of “donor–acceptor”-type platinum catalysts that are highly effective in both hydroalkoxylation and hydroamination of unactivated alkenes over a broad range of substrates under mild conditions. A number of alkene substitution patterns were accommodated, including tri-substituted, 1,1-disubstituted, (E)-disubstituted, (Z)-disubstituted and even mono-substituted double bonds. Detailed mechanistic investigations suggest a plausible pathway that includes an unexpected dissociation/re-association of the electron-deficient ligand to form an alkene-bound “donor–acceptor”-type intermediate. These mechanistic studies help understand the origins of the high reactivity exhibited by the catalytic system, and provide a foundation for the rational design of chiral catalysts towards asymmetric hydrofunctionalization reactions.

scholarly journals Halogen-bonding-promoted Photo-induced C–X Borylation of Aryl Halide using Phenol Derivatives

2022 ◽  
Author(s):  
Kazuki Matsuo ◽  
Eiji Yamaguchi ◽  
Akichika Itoh
Keyword(s):  
Functional Group ◽  
Aryl Halide ◽  
Halogen Bonding ◽  
Mechanistic Studies ◽  
Boronate Esters ◽  
Aryl Radicals ◽  
Phenol Derivatives ◽  
Mild Conditions ◽  
Donor Acceptor ◽  
Photo Induced Electron Transfer

This study investigates the photo-induced C–X borylation reaction of aryl halides by forming a halogen-bonding complex. The method employs 2-naphthol as a halogen-bonding acceptor and proceeds under mild conditions without a photoredox catalyst under 420 nm blue light irradiation. The method is highly chemoselective, broadly functional group tolerant, and provides concise access to corresponding boronate esters. Mechanistic studies reveal that forming the halogen-bonding complex between aryl halide and naphthol acts as an electron donor-acceptor complex to furnish aryl radicals through photo-induced electron transfer.

scholarly journals Micellar photocatalysis enables divergent C-H arylation and N dealkylation of benzamides via N-acyliminium cations

2022 ◽  
Author(s):  
Martyna Cybularczyk-Cecotka ◽  
Jędrzej Predygier ◽  
Stefano Crespi ◽  
Joanna Szczepanik ◽  
Maciej Giedyk
Keyword(s):  
Methylene Blue ◽  
Light Source ◽  
Catalytic System ◽  
Chemical Space ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Reducing Conditions ◽  
Benzamide Derivatives

Micellar photocatalysis has recently opened new avenues to activate strong carbon halide bonds. So far, however, it has mainly explored strongly reducing conditions restricting the available chemical space to radical or anionic reactivity. Here, we demonstrate a radical-polar crossover process involving cationic intermediates, which enables chemodivergent modification of chlorinated benzamide derivatives via either C H arylation or N dealkylation. The catalytic system operates under mild conditions employing methylene blue as a photocatalyst and blue LEDs as the light source. Factors determining the reactivity of substrates and preliminary mechanistic studies are presented.

Designing Rh(I)-Half-Sandwich Catalysts for Alkyne [2+2+2] Cycloadditions

Synlett ◽  
2020 ◽  
Author(s):  
Laura Orian ◽  
F. Matthias Bickelhaupt
Keyword(s):  
Rational Design ◽  
Computational Studies ◽  
Synthetic Route ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Aromatic Ligand ◽  
Polycyclic Aromatic ◽  
Metal Catalyzed ◽  
Cyclopentadienyl Anion ◽  
Half Sandwich

AbstractMetal-mediated [2+2+2] cycloadditions of unsaturated molecules to cyclic and polycyclic organic compounds are a versatile synthetic route affording good yields and selectivity under mild conditions. In the last two decades, in silico investigations have unveiled important details about the mechanism and the energetics of the whole catalytic cycle. Particularly, a number of computational studies address the topic of half-sandwich catalysts which, due to their structural fluxionality, have been widely employed, since the 1980s. In these organometallic species, the metal is coordinated to an aromatic ring, typically the ubiquitous cyclopentadienyl anion, C5H5 –(Cp) or to the Cp moiety of a larger polycyclic aromatic ligand (Cp′). During the catalytic process, the metal continuously ‘slips’ on the ring, changing its hapticity. This phenomenon of metal slippage and its implications for the catalyst’s performance are discussed in this work, referring to the most important computational mechanistic studies reported in literature for Rh(I) half-metallocenes, with the purpose of providing hints for a rational design of this class of compounds.1 Introduction2 Mechanism of Metal-Catalyzed Acetylene [2+2+2] Cycloaddition to Benzene and the Problem of the Indenyl Effect2.1 Acetylene-Acetonitrile [2+2+2] Co-cycloaddition to 2-Methylpyridine: Evidence of the Indenyl Effect2.2 Heteroaromatic Catalysts and the Evidence of a Reverse Indenyl Effect2.3 Booth’s Mechanistic Hypothesis and the Evidence of the Indenyl Effect3 Structure–Reactivity Correlation: The Slippage-Span Model4 Conclusions and Perspectives

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

2019 ◽  
Author(s):  
Caleb Karmel ◽  
Zhewei Chen ◽  
John Hartwig
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Activity Analysis ◽  
High Reactivity ◽  
High Yield ◽  
Phen Ligand ◽  
Mechanistic Studies ◽  
Phenanthroline Ligand ◽  
First Time ◽  
New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]<sub>2</sub> and 2,9-Me<sub>2</sub>-phenanthroline (2,9-Me<sub>2</sub>phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H<sub>2</sub> byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me<sub>2</sub>phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me<sub>2</sub>phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

Practical allylation with unactivated allylic alcohols under mild conditions

2021 ◽  
Author(s):  
Shuangshuang Li ◽  
Ju Qiu ◽  
Bowen Li ◽  
Zuolian Sun ◽  
Peizhong Xie ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Catalytic System ◽  
Allylic Alcohols ◽  
Mild Conditions ◽  
Accelerate Proton

A practical palladium/calcium catalytic system was developed for dehydrative allylation concerning unactivated allylic alcohols. EtOH solvent with H2O additive was identified as powerful media to accelerate proton transfer. That catalytic...

scholarly journals Rational Design of TADF Polymers Using a Donor-Acceptor Monomer with Enhanced TADF Efficiency Induced by the Energy Alignment of Charge Transfer and Local Triplet Excited States

2016 ◽  
Vol 4 (4) ◽  
pp. 597-607 ◽  
Author(s):  
Roberto S. Nobuyasu ◽  
Zhongjie Ren ◽  
Gareth C. Griffiths ◽  
Andrei S. Batsanov ◽  
Przemyslaw Data ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Rational Design ◽  
Donor Acceptor ◽  
Triplet Excited States

scholarly journals Asymmetric Addition of Allylsilanes to Aldehydes – A Cr/Photoredox Dual Catalytic Approach Complementing the Hosomi–Sakurai Reaction

2021 ◽  
Author(s):  
Felix Schäfers ◽  
Subhabrata Dutta ◽  
Roman Kleinmans ◽  
Christian Mück-Lichtenfeld ◽  
Frank Glorius
Keyword(s):  
Organic Chemistry ◽  
Transition State ◽  
Bioactive Compound ◽  
General Strategy ◽  
Acid Activation ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Homoallylic Alcohols ◽  
Synthetic Utility ◽  
Fundamental Transformation

The allylation of aldehydes is a fundamental transformation in synthetic organic chemistry. Among the multitude of available reagents, especially allylsilanes have been established as preferred allyl source. As initially reported by Hosomi & Sakurai, these non-toxic and highly stable reagents add to carbonyls via an open transition state upon Lewis acid activation. Herein, we report a general strategy to access a variety of valuable homoallylic alcohols in opposite chemo- and diastereoselectivity to the established Hosomi–Sakurai conditions by switching to photocatalytic activation in combination with a closed transition state (Chromium catalysis). Moreover, this dual catalytic approach displays a straightforward way to introduce excellent levels of enantioselectivity and its mild conditions allow for a broad substrate scope including chiral boron-substituted products as a highlight. To emphasize the synthetic utility, our method was applied as the key step in the synthesis of a bioactive compound and in the late-stage functionalization of steroid derivatives. Detailed mechanistic studies and DFT calculations hint towards an unprecedented photo-initiated chain being operative.

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