Visible-Light Mediated Oxidative C–H/N–H Cross-Coupling between Tetrahydrofuran and Azoles Using Air

Zhang, Lingling; Yi, Hong; Wang, Jue; Lei, Aiwen

doi:10.1021/acs.joc.7b01841

Cited by 70 publications

(23 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It should be noted that our methodology compares favorably to thermal approaches relying on TBAI/TBHP [19] (TBAI=tetrabutylammonium iodide) and Fe III /TBHP [20] systems as it requires more controlled and milder conditions to generate the oxocarbenium ion, resulting in a broader functional group tolerance. Furthermore, in comparison to other photocatalytic [21] and (photo)electrochemical methods,[ 22 , 23 ] the developed approach is based on a direct and mild C(sp 3 )−H cleavage, presents a broader scope and does not require pre‐functionalization of the starting materials.…”

mentioning

confidence: 99%

Decatungstate‐Mediated C(sp³)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

et al. 2021

View full text Add to dashboard Cite

Photocatalytic hydrogen atom transfer is a very powerful strategy for the regioselective C(sp 3 )-H functionalization of organic molecules. Herein, we report on the unprecedented combination of decatungstate hydrogen atom transfer photocatalysis with the oxidative radical-polar crossover concept to access the direct net-oxidative C(sp 3 )-H heteroarylation. The present methodology demonstrates a high functional group tolerance (40 examples) and is scalable when using continuous-flow reactor technology. The developed protocol is also amenable to the late-stage functionalization of biologically relevant molecules such as stanozolol, (À)ambroxide, podophyllotoxin, and dideoxyribose.Photocatalytic hydrogen atom transfer (HAT) is witnessing an ever-growing interest from the synthetic community as a versatile strategy for the late-stage functionalization of C(sp 3 )ÀH bonds. [1][2][3] In this activation mode, the excited state of a photocatalyst can be conveniently exploited to cleave C(sp 3 ) À H bonds to obtain carbon-centered radicals. By exploiting inherent electronic and steric properties of the parent molecule and by tuning the reaction conditions, these nucleophilic radicals can be obtained with high regioselectiv-ity, thus obviating the need to use any directing or activating groups (Scheme 1 a).Amongst the different HAT photocatalysts, the decatungstate anion (W; [W 10 O 32 ] 4À ) has proven to be an ideal candidate owing to its unique selectivity, robustness and ease of preparation. [4,5] The excited state of W (W*) can be readily obtained upon exposure to UV-A light (l > 365 nm) and has been used for the activation of C(sp 3 )ÀH bonds within a wide variety of hydrogen donors such as ethers, aldehydes, amides and even alkanes. In most cases, the fleeting radical intermediates were used to forge CÀC, [6] CÀF, [7] and CÀO [8] bonds. In contrast, only a handful of examples demonstrate the formation of C À N bonds. [9] These examples mainly rely on the trapping of the radical with a suitable Michael acceptor, e.g., diisopropyl azodicarboxylate (DIAD), delivering the corresponding hydrazides. Despite its synthetic utility to Scheme 1. a) Photocatalytic hydrogen atom transfer (HAT) enables the conversion of CÀH bonds in complex biologically active molecules. b) Established mechanism for the formation of CÀN bonds via TBADT-mediated HAT. c) Proposed approach to realize the regioselective CÀH bond heteroarylation through combination of decatungstateenabled HAT and Radical-Polar Crossover (RPC).

show abstract

mentioning

confidence: 99%

Decatungstate‐Mediated C(sp³)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

et al. 2021

View full text Add to dashboard Cite

show abstract

“…In 2017, Lei and co‐workers reported a visible light‐mediated coupling reaction between azoles and THF using oxygen as a benign oxidant (Scheme ) . No desired product was detected without light and air, which indicated that they are necessary for this coupling reaction.…”

Section: Azoles As Nitrogen Sourcementioning

confidence: 99%

Recent Progress in the Construction of C−N Bonds via Metal‐Free Radical C(sp³)−H Functionalization

Song

Meng

et al. 2020

Adv Synth Catal

View full text Add to dashboard Cite

Nitrogen‐containing compounds widely exist in pharmaceuticals and multifunctional materials. Thus, the development of C−N bond formation reactions is of great importance in synthetic chemistry. Since 2014, obvious progress has been made in the construction of C−N bonds via metal‐free radical C(sp3)−H functionalization, which is one of the major protocols due to its high reaction activity and mild conditions. To the best of our knowledge, there are still no exclusive reviews about the formation of C−N bonds through metal‐free radical C(sp3)−H functionalization. This review aims to highlight the recent advances in this area since 2014, according to the type of the nitrogen source (amines, amides, sulfonamides, azoles, azides and other nitrogen sources). The paper is focused on discussions about the reaction mechanisms and selected examples of substrates have also been listed.

show abstract

“…The reaction was achieved by using an acridinium catalyst and oxygen as the oxidant (Scheme 37). 41 The excited photocatalyst undergoes a SET process with pyrazole to generate an N-centered radical for the subsequent coupling reaction.…”

Section: Scheme 36 Cu-catalyzed Asymmetric C-n Coupling Reactionmentioning

confidence: 99%

Recent Advances in Photocatalytic C–N Bond Coupling Reactions

Chan

Chow

2020

Synthesis

View full text Add to dashboard Cite

Catalytic C–N bond formation is one of the major research topics in synthetic chemistry owing to the ubiquity of amino groups in natural products, synthetic intermediates and pharmaceutical agents. In parallel with well-established metal-catalyzed C–N bond coupling protocols, photocatalytic reactions have recently emerged as efficient and selective alternatives for the construction of C–N bonds. In this review, the progress made on photocatalytic C–N bond coupling reactions between 2012 and February 2020 is summarized.1 Introduction1.1 General Mechanisms for Photoredox Catalysis1.2 Pioneering Work2 C(sp2)–N Bond Formation2.1 Protocols Involving an External Oxidant2.2 Oxidant-Free Protocols3 C(sp3)–N Bond Formation3.1 Direct Radical–Radical Coupling3.2 Addition Reactions to Alkenes3.3 Reductive Amination of Carbonyl Compounds3.4 Decarboxylative Amination4 Cyclization Reactions4.1 C(sp2)–N Heterocycle Formation4.2 C(sp3)–N Heterocycle Formation5 Other Examples6 Conclusion and Outlook

show abstract

Visible-Light Mediated Oxidative C–H/N–H Cross-Coupling between Tetrahydrofuran and Azoles Using Air

Cited by 70 publications

References 47 publications

Decatungstate‐Mediated C(sp³)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

Decatungstate‐Mediated C(sp³)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

Recent Progress in the Construction of C−N Bonds via Metal‐Free Radical C(sp³)−H Functionalization

Recent Advances in Photocatalytic C–N Bond Coupling Reactions

Contact Info

Product

Resources

About

Visible-Light Mediated Oxidative C–H/N–H Cross-Coupling between Tetrahydrofuran and Azoles Using Air

Cited by 70 publications

References 47 publications

Decatungstate‐Mediated C(sp3)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

Decatungstate‐Mediated C(sp3)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

Recent Progress in the Construction of C−N Bonds via Metal‐Free Radical C(sp3)−H Functionalization

Recent Advances in Photocatalytic C–N Bond Coupling Reactions

Contact Info

Product

Resources

About

Decatungstate‐Mediated C(sp³)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

Decatungstate‐Mediated C(sp³)–H Heteroarylation via Radical‐Polar Crossover in Batch and Flow

Recent Progress in the Construction of C−N Bonds via Metal‐Free Radical C(sp³)−H Functionalization