Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• review highlights recent total syntheses that incorporate the best of both worlds. Keywords: biomimetic synthesis; cascades; common scaffold; hydrogen atom transfer; photoredox catalysis; Introduction Societal needs push sciences into new directions, as the urge for new pharmaceutical leads grows, in

• reactions of transition metal hydrides (Fe, Co, Mn, etc) with alkenes (e.g., Mukaiyama hydration) [20]. The last decade saw the development of milder methods for generating carbon-centered radicals as the advancement of their reactivity in cross-coupling reactions, the concept of photoredox catalysis [21

• radical to circumvent the unsuccessful Friedel–Crafts reaction. Prior reports implicated β-keto radical formation in the ring opening of siloxycyclopropanes with photoinduced electron transfer (PET) to 1,4-dicyanonaphthalene [65]. Inspired by reports on dual photoredox and Ni-catalytic cross-coupling

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• redox-neutral asymmetric organocatalysis, whereas organocatalysis by redox-active molecules stays in the shadows. For example, redox-active organic molecules are almost not mentioned in some recent overviews of compound types used in organocatalysis [3][12][13], except for photoredox catalysts [12][13

• cycle turnover. The subclass of such reactions in which a catalyst is activated by light (photoredox catalysis, Scheme 1, type IV), especially visible, has gained much attention in the last decade. A considerable number of good reviews was published, both general [19][20][21][22][23][24][25][26][27][28

• photoredox-catalyst or electrochemically on an anode. An example of the photochemical aerobic benzylic CH-oxidation employing a heterogeneous photoredox catalyst, nanosized TiO2, was demonstrated by our group [85] (Scheme 9). Mixing of NHPI and TiO2 leads to the emergence of visible light absorbance

Molecular and macromolecular electrochemistry: synthesis, mechanism, and redox properties

• Shinsuke Inagi and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 1505–1506, doi:10.3762/bjoc.18.158

• , polymer electrolyte membrane electrolysis technology, and new methods coupled with photoredox catalysts or transition metal catalysis, resulting in remarkable progress in organic electrosynthetic processes. Theoretical calculations have also led to a better understanding of the electron transfer behavior

Electrochemical formal homocoupling of sec-alcohols

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masashi Shiota,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• ][16][17][18]. In addition to the reductive coupling of carbonyl compounds, oxidative homocoupling reactions of benzyl alcohols under transition metal- or semiconductor-based photoredox catalysis have been demonstrated as attractive approaches to access vic-1,2-diols [19][20][21][22][23

Electrochemical vicinal oxyazidation of α-arylvinyl acetates

• Yi-Lun Li,
• Zhaojiang Shi,
• Tao Shen and
• Ke-Yin Ye

Beilstein J. Org. Chem. 2022, 18, 1026–1031, doi:10.3762/bjoc.18.103

• generate azidoketones. Remarkably, photoredox [12] and electrochemical [13] oxyazidation of vinylarenes are also becoming competent synthetic approaches. Besides vinylarenes, vinyl acetates are potentially versatile precursors for the anticipated vicinal oxyazidation. For instance, Singh and co-workers

DDQ in mechanochemical C–N coupling reactions

• Shyamal Kanti Bera,
• Rosalin Bhanja and
• Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

• as C–P [17], C–O [18][19][20], and C–S [21] were achieved using DDQ as an oxidant [22][23]. In addition, the utilization of DDQ as a photoredox catalyst [24] and co-catalyst [25][26] have also been documented in organic synthesis [27]. DDQ-mediated oxidative C–N cross-coupling reactions are well

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• catalysts that allow ON/OFF reaction control in photoredox catalysis [120], phosphate diester transesterification [121], Friedel–Crafts reaction, ring opening of epoxides, oligomerization [116], and acyl-transfer reactions [122][123]. While there are further examples by Mirkin [124][125][126], Schmittel

Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

• Zhihang Bai,
• Krishnasamy Velmurugan,
• Xueqi Tian,
• Minzan Zuo,
• Kaiya Wang and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2022, 18, 429–437, doi:10.3762/bjoc.18.45

• chromophoric dye molecules can be utilized in photoredox reactions under the irradiation of light with suitable wavelength [6]. However, in the case of the m-TPEWP5G-EsY nanosystem, which contains conjugated molecules and displays harvesting antenna effects from ultraviolet to visible light wavelengths, solar

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• (route (5)). However, these methods involve the use of toxic acids, bases, or transition metal catalysts, and typically require elevated temperatures [14][15][16][17][18][19][20]. In addition, very recently, Molander and co-workers have developed a photoredox-mediated radical/polar crossover process

Earth-abundant 3d transition metals on the rise in catalysis

• Nikolaos Kaplaneris and
• Lutz Ackermann

Beilstein J. Org. Chem. 2022, 18, 86–88, doi:10.3762/bjoc.18.8

• functionalization enabled the de novo assembly of bioactive molecules [9]. The full potential of the mild nature of C–H functionalization is unlocked by the merger with modern photochemistry and electrocatalysis manifolds. In this context, recent advances were realized by the combination of photoredox catalysis and

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• , molecular oxygen as the oxidant, and TiO2-immobilized ruthenium(II) polyazine complex as the heterogeneous photoredox catalyst in methanol at room temperature (Table 1). The substrate scope studies revealed a better reactivity of aromatic tertiary amines substituted with electron-donating groups compared to

• conditions, readily available reagents, lower catalyst loading, and the use of cost effective atmospheric oxygen and visible light are the most attractive characteristics of this reaction. Xu et al. in 2016 discussed the deboronative cyanation of alkyltrifluoroborates using [Ru(bpy)3](PF6)2 as the photoredox

• , alkynes, and halides were compatible with this strategy. A photoredox-catalyzed oxidative coupling of 4-alkyl-3,4-dihydroquinoxalin-2(1H)-ones with nucleophiles was reported by Hong and co-workers [42]. The reaction was performed using 20 mol % of Ru(bpy)3Cl2.6H2O in methanol under CFL light irradiation

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• is reduced by the photocatalyst (PC−) after coordination to aryl bromide, promoting the turnover of organometallic and photoredox cycles. DABCO is regenerated via deprotonation by an inorganic base. We also investigated the mechanism operating when the reaction is performed in the absence of bicyclic

• endergonic with barriers lower than the one presented for the reaction with 1 (see Supporting Information File 1, Table S7). Conclusion In conclusion, we report the use of DABCO as a HAT abstractor for aldehyde activation in a photoredox strategy. Several aryl ketones were synthesized with moderate to

• excellent yields from a range of different aldehydes and aryl bromides, showing the reaction possesses a good tolerance for substrate stereoelectronics. DABCO is a promising new alternative to expand the toolbox of bicyclic amine abstractors for photoredox HAT reactions, with an appealing low cost

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• and 1,3-dicarbonyl compounds 84 via synergistic photoredox/iron catalysis (Scheme 14) [90]. This protocol parallels Li’s seminal report in 2007 [44]; however, under these reaction conditions, the reactive radical was propagated across an alkene before termination with the activated methylene unit

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• substitution process. For example, compound 3b reacted with difluoroenolate to form the difluoroalkylated diarylmethane 5 in 83% yield via a Cu(OAc)2-catalyzed hydrodifluoroalkylation reaction [52]. Two other examples were the use of photoredox catalysis to generate acyl anions in situ from aromatic carboxylic

Electrocatalytic C(sp³)–H/C(sp)–H cross-coupling in continuous flow through TEMPO/copper relay catalysis

• Bin Guo and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2021, 17, 2650–2656, doi:10.3762/bjoc.17.178

• temperatures [3][4][5], prompting the development of mild conditions by merging photoredox catalysis with copper catalysis (Scheme 1B) [8][9]. Notwithstanding of these outstanding achievements, noble metal-based catalysts and chemical oxidants are employed under these photochemical conditions. Organic

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• Yajing Zhang Qian Wang Zongsheng Yan Donglai Ma Yuguang Zheng Traditional Chinese Medicine Processing Technology Innovation Center of Hebei Province, Hebei University of Chinese Medicine, Shijiazhuang, 050200, P. R. China 10.3762/bjoc.17.169 Abstract Photoredox catalysis has been applied to

• renewable energy and green chemistry for many years. Ruthenium and iridium, which can be used as photoredox catalysts, are expensive and scarce in nature. Thus, the further development of catalysts based on these transition metals is discouraged. Alternative photocatalysts based on copper complexes are

• ; mechanisms of copper photocatalysis; photoinduced copper-based catalysis; photoredox catalysis; special features of copper photocatalysis; Introduction Solar light is an inexhaustible and free energy source for green plants and bacteria. Photosynthetic organisms absorb solar energy and convert it into

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• absorption, and novel electronic band structure, fills the gap between graphene and wide bandgap semiconductors [35][38]. Furthermore, BP shows a layer thickness tunable bandgap ranging between 0.3 and 2.1 eV. Therefore, BPNs can efficiently be applied as a photoredox catalyst with broadband solar absorption

• [34][38][39][40]. The use of 2D materials for the photoinitiated electron transfer reactions with CuII catalysts for the photoinduced atom transfer radical polymerization (ATRP) and CuAAC reactions prompted us to develop a new photoredox system that works under NIR irradiation for the CuAAC reaction

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• visible light photoredox-catalyzed cyclizations also afforded phenanthridines (Figure 2, reaction 3) [11]. Inspired by the Rodrıguez and Walton approach, we sought to synthesize the nitrogen analogue of an angucycline known as phenanthroviridone 6, [12] from oxime 7 (Scheme 1). Based on the results

• . Once intermediate 18b is formed an H+ is abstracted by an acetate ion from the methoxy substituent again forming formaldehyde and acetic acid, along with subsequent quenching of the cation to restore aromaticity. Examples of photoredox-catalyzed cation radical accelerated reactions with the aromatic

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• salts; Green Chemistry; Meerwein arylation; photoredox; Introduction Quinones or quinoid-based structures are ubiquitous in nature [1][2][3]. These versatile structures have shown promising antimalarial [4][5], antibacterial [6], and chemotherapeutic [6][7][8] properties. Their inherent oxidative

• journal [22]. Attempts at reducing aryldiazonium salts organocatalytically have also been successful [23][24][25][26]. Inspired by the seminal work by Sanford [27], König et al. [28] designed a simple and effective CH-arylation reaction combining diazonium chemistry with photoredox catalysis. By using

• combining photoredox and diazonium chemistry. By starting from the commercially available 2,5-dichlorobenzoquinone (1), we eliminate the issue of regioselectivity and effectively create a green synthesis pathway towards a versatile bis-electrophile. Results and Discussion We initiated our investigation by

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• metallaphotoredox catalysis enabled C‒H functionalizations with unique reaction pathways under mild reaction conditions. Given the relative earth-abundance and cost-effective nature, nickel catalysts for photoredox C‒H functionalization have received significant attention. In this review, we highlight the

• developments in the field of photoredox nickel-catalyzed C‒H functionalization reactions with a range of applications until summer 2021. Keywords: C–H activation; functionalization; nickel; photocatalysts; photoredox; visible light; Introduction During the last decades, transition-metal-catalyzed

• often requires relatively high catalyst loadings, directing groups, high reaction temperatures (100–160 °C), stoichiometric additives, or oxidants such as peroxide or silver salts that can be undesirable for large scale synthesis. Recently, photoredox dual catalysis has witnessed significant

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• retinoic acid receptor agonist analogue 63 and an estrone acetate derivative 64 (Scheme 22D). A seminal work involving manganese-catalyzed C–H organic electrosynthesis and photoredox catalysis was reported in the same year by Lei and co-workers, also regarding the azidation of alkyl scaffolds (Scheme 23A

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• synthesis [32][33][34][35]. Integration of g-CN into hydrogels has been popularized in the last four years, where g-CN nanosheets can be implemented into hydrogels through embedding [36] or covalent binding [37][38] for the target application such as reinforced hydrogels [39] and hydrogels for photoredox

• vTA, then exposed to visible light irradiation to initiate an in situ surface photomodification. Extensive studies over the last years demonstrated photoinduced g-CN surface modification methods through a photoredox system. vTA, which is a common food additive to donate a nutty taste, has previously

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• microwave stimulations [18][19][20][21][22][23][24][25][26]. Recently, visible light photoredox catalysis has emerged as a powerful and environment-friendly method in organic synthesis by activating organic molecules under mild reaction conditions [27][28]. In this context, the Li and Cai groups

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• synthesis has encouraged chemists to pursue more efficient methods to manufacture fine and usable chemicals [7]. The reactions that EDA complexes participate in have been shown to be an enormous success, mainly due to the fact that they obviate photoredox catalysts or transition metal catalysts in the vast

• [76]. Cases of C–P bond construction employing photoredox [77][78] or photoredox/nickel dual catalysis [79] have been identified in the field of photochemistry. However, here we introduce the methods initiated by EDA complexes for C–P bond construction. In 2018, Lakhdar and colleagues [44] reported a