Direct C–H Functionalization of Heteroarenes via Redox-Neutral Radical Process: A Facile Route to C–C Bonds Formation

Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3407-3421 ◽  
Author(s):  
Pin Gao ◽  
Yu-Rui Gu ◽  
Xin-Hua Duan
Keyword(s):  
Functional Group ◽  
Radical Reactions ◽  
Neutral Radical ◽  
Alkyl Radicals ◽  
Aryl Radicals ◽  
Mild Conditions ◽  
Wide Range ◽  
Carbon Radicals ◽  
Facile Route ◽  
Radical Functionalization

Aromatic heterocycles are an important class of compounds found in a wide range of natural products, pharmaceutically active molecules and organic materials. Recently, the direct radical functionalization of heteroaromatic C–H bonds has become an efficient and attractive method to access substituted heteroarenes. Especially, redox-neutral radical reactions have attracted much attention of chemists due to their potential advantages such as mild conditions, free of external oxidants, and good functional group tolerance. So far, a series of redox-neutral radical reactions have been developed. In this review, we mainly focus on the recent advance in direct redox-neutral radical C–H functionalization of heteroarenes. Herein, the direct C–H arylation, C–H alkylation, and C–H fluoroalkylation of heteroarenes are represented respectively, providing practical routes to C–C bond formation.1 Introduction2 C–H Arylation of Heteroarenes with Aryl Radicals3 C–H Alkylation of Heteroarenes with Alkyl Radicals4 C–H Fluoroalkylation of Heteroarenes with Fluorine-Containing Carbon Radicals5 Concluding Remarks

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.

Additive- and Oxidant-Free Expedient Synthesis of Benzimidazoles Catalyzed by Cobalt Nanocomposites on N-Doped Carbon

Synlett ◽  
2019 ◽  
Vol 30 (03) ◽  
pp. 319-324 ◽  
Author(s):  
Zhaozhan Wang ◽  
Tao Song ◽  
Yong Yang
Keyword(s):  
Functional Group ◽  
Direct Synthesis ◽  
Biologically Active ◽  
One Pot ◽  
Mild Conditions ◽  
Wide Range ◽  
High Yields

A one-pot direct synthesis of a wide range of biologically active benzimidazoles through coupling of phenylenediamines and aldehydes catalyzed by a highly recyclable nonnoble cobalt nanocomposite was developed. A broad set of benzimidazoles can be efficiently synthesized in high yields and with good functional-group tolerance under additive- and oxidant-free mild conditions. The catalyst can be easily recycled for successive uses, and the process permits gram-scale syntheses of benzimidazoles.

scholarly journals Palladium-Catalyzed Cross-Coupling of Gem-Bromofluoroalkenes with Alkylboronic Acids for the Synthesis of Alkylated Monofluoroalkenes

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5532
Author(s):  
Laëtitia Chausset-Boissarie ◽  
Nicolas Cheval ◽  
Christian Rolando
Keyword(s):  
Organic Synthesis ◽  
Functional Group ◽  
Materials Science ◽  
Cross Coupling ◽  
High Yield ◽  
Efficient Synthesis ◽  
Mild Conditions ◽  
Wide Range ◽  
Palladium Catalyzed ◽  
Novel Strategy

Monofluoroalkenes are versatile fluorinated synthons in organic synthesis, medicinal chemistry and materials science. In light of the importance of alkyl-substituted monofluoroalkenes efficient synthesis of these moieties still represents a synthetic challenge. Herein, we described a mild and efficient methodology to obtain monofluoroalkenes through a stereospecific palladium-catalyzed alkylation of gem-bromofluoroalkenes with primary and strained secondary alkylboronic acids under mild conditions. This novel strategy gives access to a wide range of functionalized tri- and tetrasubstituted monofluoroalkenes in high yield, with good functional group tolerance, independently from the gem-bromofluoroalkenes geometry.

Iridium(III)-Catalyzed Difluoroalkylation–Bicyclization of 1,7-Enynes toward Benzo[a]fluoren-5-ones under Visible-Light Photoredox Conditions

Synthesis ◽  
2020 ◽  
Vol 52 (24) ◽  
pp. 3865-3873
Author(s):  
Wen-Juan Hao ◽  
Bo Jiang ◽  
Min-Hua Huang
Keyword(s):  
Visible Light ◽  
Functional Group ◽  
High Efficiency ◽  
Mild Conditions ◽  
Wide Range

A new visible-light-induced Ir(III)-catalyzed difluoroalkylation–bicyclization of 1,7-enynes with ethyl 2-bromo-2,2-difluoroacetate (BrCF2CO2Et) is described, furnishing a wide range of difluoromethyl-containing benzo[a]fluoren-5-ones in good to excellent yields. The reaction is operationally simple, proceeds with high efficiency under mild conditions, and shows excellent functional group compatibility.

scholarly journals Boron: A key element in radical reactions

2007 ◽  
Vol 79 (2) ◽  
pp. 223-233 ◽  
Author(s):  
Philippe Renaud ◽  
Alice Beauseigneur ◽  
Andrea Brecht-Forster ◽  
Barbara Becattini ◽  
Vincent Darmency ◽  
...  
Keyword(s):  
Chain Transfer ◽  
High Sensitivity ◽  
Conjugate Addition ◽  
Radical Reactions ◽  
Radical Chain ◽  
Alkyl Radicals ◽  
Wide Range ◽  
A Chain ◽  
Very High ◽  
Tertiary Alkyl

Boron derivatives are becoming key reagents in radical chemistry. Here, we describe reactions where an organoboron derivative is used as a radical initiator, a chain-transfer reagent, and a radical precursor. For instance, B-alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary, and tertiary alkyl radicals. Their very high sensitivity toward oxygen- and heteroatom-centered radicals makes them particularly attractive for the development of radical chain processes such as conjugate addition, allylation, alkenylation, and alkynylation. Boron derivatives have also been used to develop an attractive new procedure for the reduction of radicals with alcohols and water. The selected examples presented here demonstrate that boron-containing reagents can efficiently replace tin derivatives in a wide range of radical reactions.

scholarly journals Chiral Alkyl Amine Synthesis via Catalytic Enantioselective Hydroalkylation of Enamides

2020 ◽  
Author(s):  
Deyun Qian ◽  
Srikrishna Bera ◽  
Xile Hu
Keyword(s):  
Natural Products ◽  
Functional Group ◽  
Building Blocks ◽  
Alkyl Halides ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Drug Molecules ◽  
Alkyl Amines ◽  
Wide Range ◽  
Synthetic Intermediates

Chiral alkyl amines are omnipresent as bio-active molecules and synthetic intermediates. Catalytic and enantioselective synthesis of alkyl amines from readily accessible precursors is challenging. Here we develop a nickel-catalyzed hydroalkylation method to assemble a wide range of chiral alkyl amines from enamides and alkyl halides in high regio- and enantioselectivity. The method works for both non-activated and activated alkyl halides, and is able to produce enantiomerically enriched amines with two minimally differentiated alpha-alkyl substituents. The mild conditions lead to high functional group tolerance, which is demonstrated in the post-product functionalization of many natural products and drug molecules, as well as the synthesis of chiral building blocks and key intermediates to bio-active compounds.

scholarly journals Chiral Alkyl Amine Synthesis via Catalytic Enantioselective Hydroalkylation of Enamides

2020 ◽  
Author(s):  
Deyun Qian ◽  
Srikrishna Bera ◽  
Xile Hu
Keyword(s):  
Natural Products ◽  
Functional Group ◽  
Building Blocks ◽  
Alkyl Halides ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Drug Molecules ◽  
Alkyl Amines ◽  
Wide Range ◽  
Synthetic Intermediates

Chiral alkyl amines are omnipresent as bio-active molecules and synthetic intermediates. Catalytic and enantioselective synthesis of alkyl amines from readily accessible precursors is challenging. Here we develop a nickel-catalyzed hydroalkylation method to assemble a wide range of chiral alkyl amines from enamides and alkyl halides in high regio- and enantioselectivity. The method works for both non-activated and activated alkyl halides, and is able to produce enantiomerically enriched amines with two minimally differentiated alpha-alkyl substituents. The mild conditions lead to high functional group tolerance, which is demonstrated in the post-product functionalization of many natural products and drug molecules, as well as the synthesis of chiral building blocks and key intermediates to bio-active compounds.

scholarly journals Aryl radical-mediated N-heterocyclic carbene catalysis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuki Matsuki ◽  
Nagisa Ohnishi ◽  
Yuki Kakeno ◽  
Shunsuke Takemoto ◽  
Takuya Ishii ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Electron ◽  
Radical Reactions ◽  
Single Electron Transfer ◽  
Aryl Radical ◽  
Aryl Iodide ◽  
Alkyl Radicals ◽  
Aryl Radicals ◽  
Electron Transfer Processes ◽  
Secondary Amides

AbstractThere have been significant advancements in radical reactions using organocatalysts in modern organic synthesis. Recently, NHC-catalyzed radical reactions initiated by single electron transfer processes have been actively studied. However, the reported examples have been limited to catalysis mediated by alkyl radicals. In this article, the NHC organocatalysis mediated by aryl radicals has been achieved. The enolate form of the Breslow intermediate derived from an aldehyde and thiazolium-type NHC in the presence of a base undergoes single electron transfer to an aryl iodide, providing an aryl radical. The catalytically generated aryl radical could be exploited as an arylating reagent for radical relay-type arylacylation of styrenes and as a hydrogen atom abstraction reagent for α-amino C(sp3)–H acylation of secondary amides.

Double Ring-Closing Approach for the Synthesis of 2,3,6,7-Substituted Anthracene Derivatives

2020 ◽  
Author(s):  
Birgit Meindl ◽  
Katharina Pfennigbauer ◽  
Berthold Stöger ◽  
Martin Heeney ◽  
Florian Glöcklhofer
Keyword(s):  
Wittig Reaction ◽  
Condensation Reaction ◽  
Synthetic Methods ◽  
Anthracene Derivative ◽  
Double Ring ◽  
Mild Conditions ◽  
Wide Range ◽  
Anthracene Derivatives

Anthracene derivatives have been used for a wide range of applications and many different synthetic methods for their preparation have been developed. However, despite continued synthetic efforts, introducing substituents in some positions has remained difficult. Here we present a method for the synthesis of 2,3,6,7-substituted anthracene derivatives, one of the most challenging anthracene substitution patterns to obtain. The method is exemplified by the preparation of 2,3,6,7-anthracenetetracarbonitrile and employs a newly developed, stable protected 1,2,4,5-benzenetetracarbaldehyde as the precursor. The precursor can be obtained in two scalable synthetic steps from 2,5-dibromoterephthalaldehyde and is converted into the anthracene derivative by a double intermolecular Wittig reaction under very mild conditions followed by a deprotection and intramolecular double ring-closing condensation reaction. Further modification of the precursor is expected to enable the introduction of additional substituents in other positions and may even enable the synthesis of fully substituted anthracene derivatives by the presented approach.<br>

scholarly journals Thermo- and Photoresponsive Behaviors of Dual-Stimuli-Responsive Organogels Consisting of Homopolymers of Coumarin-Containing Methacrylate

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 329
Author(s):  
Seidai Okada ◽  
Eriko Sato
Keyword(s):  
Functional Group ◽  
Solution Temperature ◽  
Stimuli Responsive ◽  
Critical Solution Temperature ◽  
Equilibrium Degree ◽  
Stimuli Responsive Polymers ◽  
Responsive Polymers ◽  
Dual Functional ◽  
Wide Range ◽  
Increasing Temperature

Coumarin-containing vinyl homopolymers, such as poly(7-methacryloyloxycoumarin) (P1a) and poly(7-(2′-methacryloyloxyethoxy)coumarin) (P1b), show a lower critical solution temperature (LCST) in chloroform, which can be controlled by the [2 + 2] photochemical cycloaddition of the coumarin moiety, and they are recognized as monofunctional dual-stimuli-responsive polymers. A single functional group of monofunctional dual-stimuli-responsive polymers responds to dual stimuli and can be introduced more uniformly and densely than those of dual-functional dual-stimuli-responsive polymers. In this study, considering a wide range of applications, organogels consisting of P1a and P1b, i.e., P1a-gel and P1b-gel, respectively, were synthesized, and their thermo- and photoresponsive behaviors in chloroform were investigated in detail. P1a-gel and P1b-gel in a swollen state (transparent) exhibited phase separation (turbid) through a temperature jump and reached a shrunken state (transparent), i.e., an equilibrium state, over time. Moreover, the equilibrium degree of swelling decreased non-linearly with increasing temperature. Furthermore, different thermoresponsive sites were photopatterned on the organogel through the photodimerization of the coumarin unit. The organogels consisting of homopolymers of coumarin-containing methacrylate exhibited unique thermo- and photoresponsivities and behaved as monofunctional dual-stimuli-responsive organogels.

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