Visible‐Light‐Induced Meerwein Cascade Reactions for the Preparation of α‐Aryl Esters

Niu, Tengfei; Li, Liang; Ni, Bangqing; Bu, Mei‐jie; Cai, Chun; Hui-liang, Jiang

doi:10.1002/ejoc.201500659

Cited by 16 publications

(7 citation statements)

References 40 publications

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“…Imine, ( 4 ) is formed from the condensation between 1 and 2 . RB*, the excited state of RB, generated under visible light irradiation, is able to abstract an electron from imine via a single electron transfer (SET) process . The photoredox cycle is completed by the oxidation of the RB radical anion back to the ground state RB by dioxygen.…”

Section: Resultsmentioning

confidence: 99%

An Efficient Synthesis of 2-Substituted Benzimidazoles via Photocatalytic Condensation of o-Phenylenediamines and Aldehydes

et al. 2016

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A photocatalytic method has been developed for the efficient synthesis of functionalized benzimidazoles. This protocol involves photocatalytic condensation of o-phenylenediamines with various aldehydes using the Rose Bengal as photocatalyst. The method was found to be general and was successfully employed for accessing pharmaceutically important benzimidazoles by the condensation of aromatic, heteroaromatic and aliphatic aldehydes with o-phenylenediamines, in good-to-excellent yields. Notably, the method was found to be effective for the condensation of less reactive heterocyclic aldehydes with o-phenylenediamines.

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Section: Resultsmentioning

confidence: 99%

An Efficient Synthesis of 2-Substituted Benzimidazoles via Photocatalytic Condensation of o-Phenylenediamines and Aldehydes

et al. 2016

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“…105 A range of other ruthenium photocatalyzed radical additions to nucleophiles with p systems have been reported, including fluoroalkylations 49,[106][107][108][109][110][111][112][113][114][115][116][117][118][119][120][121] and the arylation of styrenes and enol acetates 122 among others. 58,[123][124][125][126][127][128] Again, some of these systems rely on the oxidative quenching of excited state *Ru(bpy) 3…”

Section: +mentioning

confidence: 99%

Photocatalysis in organic and polymer synthesis

et al. 2016

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This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists.

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“… DMF was employed to generate the Vilsmeier reagent. Jiang et al reported the synthesis of α-aryl esters utilizing visible-light-induced Meerwein cascade reaction using aryl diazonium salts, acrylonitrile, O 2 , Ru(bpy) 3 Cl 2 ·6H 2 O as photocatalyst, and alcohols as both reagent and solvent …”

Section: Arylation Reactions Using Aryl Diazonium Saltsmentioning

confidence: 99%

Visible Light Mediated Photoredox Catalytic Arylation Reactions

et al. 2016

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Introducing aryl- and heteroaryl moieties into molecular scaffolds are often key steps in the syntheses of natural products, drugs, or functional materials. A variety of cross-coupling methods have been well established, mainly using transition metal mediated reactions between prefunctionalized substrates and arenes or C-H arylations with functionalization in only one coupling partner. Although highly developed, one drawback of the established sp2-sp2 arylations is the required transition metal catalyst, often in combination with specific ligands and additives. Therefore, photoredox mediated arylation methods have been developed as alternative over the past decade. We begin our survey with visible light photo-Meerwein arylation reactions, which allow C-H arylation of heteroarenes, enones, alkenes, and alkynes with organic dyes, such as eosin Y, as the photocatalyst. A good number of examples from different groups illustrate the broad application of the reaction in synthetic transformations. While initially only photo-Meerwein arylation-elimination processes were reported, the reaction was later extended to photo-Meerwein arylation-addition reactions giving access to the photoinduced three component synthesis of amides and esters from alkenes, aryl diazonium salts, nitriles or formamides, respectively. Other substrates with redox-active leaving groups have been explored in photocatalyzed arylation reactions, such as diaryliodonium and triarylsulfonium salts, and arylsulfonyl chlorides. We discus some examples with their scope and limitations. The scope of arylation reagents for photoredox reactions was extended to aryl halides. The challenge here is the extremely negative reduction potential of aryl halides in the initial electron transfer step compared to, e.g., aryl diazonium or diaryliodonium salts. In order to reach reduction potentials over -2.0 V vs SCE two consecutive photoinduced electron transfer steps were used. The intermediary formed colored radical anion of the organic dye perylenediimide is excited by a second photon allowing the one electron reduction of acceptor substituted aryl chlorides. The radical anion of the aryl halide fragments under the loss of a halide ion and the aryl radical undergoes C-H arylation with biologically important pyrrole derivatives or adds to a double bond. Rhodamine 6G as an organic photocatalyst allows an even higher degree of control of the reaction. The dye is photoreduced in the presence of an amine donor under irradiation with green light (e.g., 530 nm), yielding its radical anion, which is a mild reducing reagent. The hypsochromic shift of the absorption of the rhodamine 6G radical anion toward blue region of the visible light spectrum allows its selective excitation using blue light (e.g., 455 nm). The excited radical anion is highly reducing and able to activate even bromoanisole for C-H arylation reactions, although only in moderate yield. Photoredox catalytic C-H arylation reactions are valuable alternatives to metal catalyzed reactions. They have an excellent f...

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Visible‐Light‐Induced Meerwein Cascade Reactions for the Preparation of α‐Aryl Esters

Abstract: A practical strategy has been developed for preparation of α-aryl ester derivatives by using a visible-light-induced Meerwein cascade reaction. This method uses molecular oxygen as an oxidant at room temperature without the need of hazardous reagents or harsh reaction conditions and pro-

Cited by 16 publications

References 40 publications

An Efficient Synthesis of 2-Substituted Benzimidazoles via Photocatalytic Condensation of o-Phenylenediamines and Aldehydes

An Efficient Synthesis of 2-Substituted Benzimidazoles via Photocatalytic Condensation of o-Phenylenediamines and Aldehydes

Photocatalysis in organic and polymer synthesis

Visible Light Mediated Photoredox Catalytic Arylation Reactions

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