Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• additive and K2CO3 as base in DMF under visible light irradiation. The reaction of Co(OAc)2·4H2O with 2-(hydroxyimino)-1-phenylpropan-1-one in EtOH resulted in the formation of the Co catalyst. The coupling strategy exhibited only poor activity by the use of pure Co salts and the reaction was promoted by

High-speed C–H chlorination of ethylene carbonate using a new photoflow setup

• Takayoshi Kasakado,
• Takahide Fukuyama,
• Tomohiro Nakagawa,
• Shinji Taguchi and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2022, 18, 152–158, doi:10.3762/bjoc.18.16

• ), chloroethylene carbonate (2) was obtained in good to excellent selectivity by tuning the flow rates of 1 and chlorine gas. Partial irradiation of the flow channel is sufficient for the C–H chlorination, consistent with the requirement for light irradiation for the radical initiation step. If we apply the

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

• catalyst [41]. This method provides an efficient pathway to 1°, 2°, and 3° alkyl nitriles using p‐toluenesulfonyl cyanide (TsCN) in CH2Cl2/H2O under visible-light irradiation (Scheme 17). 1‐Acetoxy‐1,2‐benziodoxol‐3‐(1H)‐one (BI‐OAc) was chosen as the oxidant and TFA as the additive in this method. A lower

• , 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

• trimethylsilyl cyanide (TMSCN) in acetonitrile solvent under CFL light irradiation. 4 Miscellaneous An efficient methodology for the synthesis of α-aminonitriles via the one-pot coupling of aldehydes, amines and trimethylsilyl cyanide was reported [46]. This reaction was catalyzed by RuCl3 and used acetonitrile

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

• Supporting Information File 1, Tables S4 and S5 for details). A plausible mechanism for the aldehyde arylation is presented in Scheme 3 based on previous literature reports [19][26][33][34] and our mechanistic investigation experiments. Upon blue light irradiation, the photocatalyst is excited generating the

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• attributed to a greater electronic conjugation provided by the imine function present in the molecules of the series 3. Photostability and singlet oxygen quantum yield (ΦΔ) assays In order to be efficient for applications in photobiology, organic dyes must be stable when subjected to light irradiation for

• possible reactive oxygen species in DMSO solution (e.g., hydroxyl and superoxide radical species) that are not identified by the type of photooxidation assay employed in this work. The good photostability and tendency of these Schiff base derivatives to generate 1O2 under light irradiation demonstrated

• solution after irradiation with white-light LED array system (400–800 nm) at a fluence rate of 25 mW/cm2 for different periods (0 to 60 min; total light dosage = 90 J/cm2). DPBF photooxidation assays by red-light irradiation with diode laser (λ = 660 nm) in the presence of quinoline 3bb (R = Ph, R1 = 5

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

• transformation under visible-light irradiation by acting as a catalyst for single-electron reduction and as an intermediate stabilizing agent (Scheme 8). In 2016, the same group [48] reported the [Cu(dap)2]Cl-catalyzed cyclization of α,ω-alkenols and trifluoromethylsulfonyl chloride to form sultones (Scheme 8

• ). Intrigued by this unique transformation, Reiser’s group [49] extended this protocol to the chlorosulfonylation of alkenes and alkynes in 2019. Under visible light irradiation and in the presence of [Cu(dap)2]Cl, the reaction of p-toluenesulfonyl chloride (7) with alkenes gave an excellent yield of the

• form the desired product 13 (Scheme 9). In 2019, the same group [56] applied this protocol to the asymmetric cyanofluoroalkylation of alkenes. Under visible-light irradiation, the Cu-based catalyst plays a dual role as both the photosensitizer for the SET and the catalyst for asymmetric control (Scheme

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

• , we present a novel synthetic methodology for the photoinduced CuAAC reaction utilizing exfoliated two-dimensional (2D) few-layer black phosphorus nanosheets (BPNs) as photocatalysts under white LED and near-IR (NIR) light irradiation. Upon irradiation, BPNs generated excited electrons and holes on

• azide derivatives under both white LED and NIR light irradiation. Due to its deeper penetration of NIR light, the possibility of synthesizing different macromolecular structures such as functional polymers, cross-linked networks and block copolymer has also been demonstrated. The structural and

• conventional 2D materials have a wide bandgap that requires UV light irradiation for their activation. Since 94% of the rays from the sun are not sufficient to activate these conventional semiconductor materials, many strategies have been proposed to design photocatalysts that can harvest in a wide spectrum of

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

• were found to be suitable to achieve the transformation in satisfactory yields under visible light irradiation (Scheme 2). The authors hypothesized that the key α-nitrogen carbon-centered radical 5 could be generated via a photoredox-driven N-phenyl oxidation and α-C–H deprotonation sequence from

• efficient HAT photocatalyst to perform the desired C–H abstraction (Scheme 10) [62]. The catalytic reaction required near-ultraviolet light irradiation (Kessil 34 W 390 nm LEDs) and the exclusion of both oxygen and water to the success of the reaction. A variety of cyclic, acyclic, and bicyclic aliphatic

• perchlorate ([Acr-Mes]+ClO4−) [64]. The reaction was conveniently achieved at room temperature under blue light irradiation. Moreover, as shown in Scheme 13, electron-deficient aryl bromides were efficient in forming the desired products 23 in optimal yields. In contrast, only trace amounts of cross-coupled

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• cyclic ketene acetals [277]. This copolymer also showed a well-controllable reversible UCST behavior in aqueous solutions. In 2020, Zhao et al. reported that by incorporating azobenzene functionalities into polyacrylamide copolymers, the responsive UCST behavior was furthermore tuneable via light

• irradiation as well as by host molecule (α-cyclodextrin) complexation [278]. Due to the high number of proton acceptor/donor sites, ureido-modified copolymers such as poly(allylamine-co-allylurea) are also becoming more and more important. The critical phase transition temperature can often be finely tuned

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

• has been selectively feasible without activating a C(sp2)–H bond in the arene moiety. Verma and co-workers [91] have reported the use of VO(acac)2 immobilized over graphitic carbon nitride (VO@gC3N4) under visible light irradiation to perform a photocatalytic C–H activation of arene methides and

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• , azidated N-protected memantine 13a was successfully generated by employing electricity and visible-light irradiation in the presence of a Mn catalyst. High regioselectivity was observed at tertiary or benzylic positions (see 13a–c). For commercially available drug derivatives, methyl esters of ibuprofen

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• product (Table 1, entry 15). Additionally, control experiments indicated that catalytic amounts of the cerium salt, air atmosphere and light irradiation were necessary for the reaction to occur (Table 1, entries 16 and 17). With the optimized reaction parameters in our hands, we next explored the

• this cerium-photocatalyzed aerobic oxidation of alcohols prompted us to conduct some preliminary mechanistic studies (Figure 1). As anticipated, the ON/OFF irradiation experiments confirmed that our reaction required a continuous blue light irradiation (see Supporting Information File 1). The

• blue light irradiation (0–180 s); (B): plausible reaction mechanism. Photocatalyzed aerobic oxidation of aromatic alcohols. Substrate scope. Reaction conditions as given in Table 1 (entry 1). Yields are isolated yields, average of at least two independent runs. Notes: athe reaction was carried using

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• traces of any β-carboline product were observed, which proves that the heterocyclization reaction is highly regiospecific. Optical properties of γ-carbolines Interestingly, the γ-carboline derivatives were found to be highly fluorescent under UV light irradiation. A systematic literature survey revealed

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

• 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

• shown a significant hydrophobization effect on bulk g-CN [45], so that a similar strategy is targeted for the present case in hydrogel systems (Scheme 2). After adequate light irradiation followed by a facile purification step, the resulting sample (HGCM-vTA) and HGCM were investigated via solid-state

• contrast to HGCM and HGCM-vTA. Moreover, the altered HGCM absorbance after surface modification provides enhanced absorption in deep UV range (Figure 1b). In addition, digital images of HG, HGCM, HGCM-vTA under UV light irradiation also reveal their emissive properties (Supporting Information File 1

Manganese/bipyridine-catalyzed non-directed C(sp³)–H bromination using NBS and TMSN₃

• Kumar Sneh,
• Takeru Torigoe and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2021, 17, 885–890, doi:10.3762/bjoc.17.74

• ][36][37][38][39][40][41][42][43]. Highly reactive and selective bromination reactions have been achieved using a stoichiometric amount of MnO2 [44] or a catalytic amount of Li2MnO3 [45] under fluorescent light irradiation in the presence of Br2 (Scheme 1d). Hill [46] and Groves [47][48][49] have

Highly regio- and stereoselective phosphinylphosphination of terminal alkynes with tetraphenyldiphosphine monoxide under radical conditions

• Dat Phuc Tran,
• Yuki Sato,
• Yuki Yamamoto,
• Shin-ichi Kawaguchi,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 866–872, doi:10.3762/bjoc.17.72

• , we examined in detail the radical addition of Ph2P(O)PPh2 to alkynes and found that the desired radical addition proceeds efficiently using a radical initiator instead of light irradiation, providing 1-(diphenylphosphinyl)-2-(diphenylphosphino)-1-alkenes (Scheme 1e). Results and Discussion First, a

• carried out varying the reaction parameters such as the light source and the ratio of the radical initiator (V-40)/2a (Table 1). Using a xenon lamp as an artificial solar source [48][49], 3a was produced in 45% yield (Table 1, entry 1). Using UV light irradiation with a high-pressure mercury lamp [50], 3a

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

• , Chengdu 610100, China 10.3762/bjoc.17.67 Abstract The reversible, weak ground-state aggregate formed by dipole–dipole interactions between an electron donor and an electron acceptor is referred to as an electron-donor–acceptor (EDA) complex. Generally, upon light irradiation, the EDA complex turns into

• -alkyl moiety in 31 or N,N-dimethylaniline (30). This approach utilizes N,N-dimethylaniline (30) as electron donor and N-methylmaleimide (31) as electron acceptor to form an EDA complex, so that single-electron transfer occurs under ultraviolet-light irradiation. Subsequently, intermolecular proton

• molar concentration of 30 was 7 times that of 31, the concentration of the EDA complex was essential for a high reaction rate. In 2018, Yu and colleagues [22] discovered a method that employed O-aryloxime 37 and triethylamine as substrates at room temperature and blue-light irradiation to give

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• combining a polyelectrolyte and an ionic azo dye [4]. Moreover, recently we have developed a switchable nano-assembly system based on photoacids [66][67]. Photoacids are molecules for which light irradiation leads to an enhanced proton dissociation and thus to a more highly charged molecule. Furthermore

• absorption maximum of form B lies in the UV region at λ = 290 nm. The open forms Cc and Ct cannot be separated and show an absorption at λ = 360 nm. Since the aim of this study was to develop a multiswitchable system that acts under light irradiation, it is also of importance that the Flavy molecule is

• step when excited by light irradiation. Due to the network of possible reactions of Flavy, self-assembly can be accessed and triggered in a number of ways. While this study focused on the first proof of concept and the relation of molecular and nanoscale switching, a deeper understanding of the

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

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

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• physical barrier in photocatalytic reactions. To address this issue, Chen and co-workers prepared a TiO2–AuNCs@β-CD-based hybrid material on TiO2 and β-CD-protected AuNCs, which can potentially be used for the photocatalytic degradation of methyl orange (MO) dye (Figure 8) [28]. Upon UV-light irradiation

• of the reactant of 300 mM, ≥93% selectivity), with H2 liberation being achieved by visible-light irradiation in an aqueous solution. In comparison, CdS–CD was a highly efficient photocatalyst for benzyl alcohol dehydrogenation (77 µmol H2 in 180 h) compared to the CD-free CdS (5.4 µmol H2 in 30 h

• , Yagi, et al. reported that the visible-light-driven hydrogen evolution of the supramolecular system could be achieved by the host–guest complexation between the cobaloxime CoPyS and γ-CD (Figure 10) [30]. Upon visible-light irradiation, the CoPyS:γ-CD 1:1 complex exhibited an enhanced photocatalytic H2

Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• studies of NO2-C9∙∙∙F4St. The photographs of the solid components as well as the formed complex under UV light irradiation (λex = 365 nm) reveal the change in fluorescent intensity upon complexation (a); fluorescence intensity plot as a function of the temperature upon heating from room temperature to 110

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction

• Vyacheslav I. Supranovich,
• Igor A. Dmitriev and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 3104–3108, doi:10.3762/bjoc.16.260

• fluorinated piperidines based on an accidentally discovered annelation reaction proceeding under reductive conditions. Results and Discussion Nitrone 1a was selected as a model substrate and it was combined with commercially available dibromide 2a under blue light irradiation in the presence of an iridium

Easy access to a carbohydrate-based template for stimuli-responsive surfactants

• Thomas Holmstrøm,
• Daniel Raydan and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2020, 16, 2788–2794, doi:10.3762/bjoc.16.229

• surfactants: amphiphilic molecules that can alter their properties upon an external stimulus [6]. The intelligent surfactants are not passive but designed to undergo a molecular change when it is triggered with either a change in the pH value [7][8], upon light irradiation [9] or in the presence of metal ions

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• -light irradiation by a household (19 W) compact fluorescent light (CFL) bulb (emitting variable wavelengths in the range of ≈365–625 nm) [195] and under mild conditions. Control reactions revealed that both the PS and light were essential for the reaction to occur. According to their report, benzylic C

• disclosed the direct C–H fluorination [201] of unactivated alkyl C(sp3)–H bonds using acetophenone as a PSCat, which was photoexcited by near-UV light (375–400 nm, Scheme 12). In the absence of a PSCat and using dedicated UV-light irradiation (275–375 nm), the product was observed together with numerous

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• directed ortho-metalation should exhibit visible-light absorption property and thus, under visible-light irradiation, the overall catalytic cycle could benefit from the photocatalytic activation. Following the initial hypothesis, the direct functionalization of phenylpyridine substrates turned out to be

• , ortho-C–H activation delivering the photoactive intermediate. Under visible-light irradiation, the SET process from the excited ruthenacycle to the haloalkane coupling partner leads to the formation of a stabilized alkyl radical (Figure 39). Next, radical attack at the para-position of the carbohydrate

• photoreactor emitting UV light at 254 nm, the same reactivity was also reached under visible-light irradiation (blue LEDs), and in the presence of the photosensitizer, Ir(ppy)3. This transformation hence illustrates clearly the potential of combining metal catalysis and photoinduction to design much milder and

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• interest in g-C3N4 photocatalysts was generated in 2009 by Wang, Domen, and co-workers, who reported the metal-free photolysis of water was possible with the all-organic semiconductor material, a sacrificial electron donor, and visible light irradiation [120]. Prior to this report, poly(p-phenylene) had