Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• paths, where consequently the requirements for the application of the Beer–Lambert law are not fulfilled anymore. Considering the inner diameter of the loop reactor of 5 cm, a catalyst loading of 0.11 g L−1 is sufficient to absorb more than 95% of the photons. Photocatalytic hydrogen evolution Long-term

• catalyst surface. Furthermore, it is evident from Figure 13a that higher inert gas flow rates decrease the irradiation time needed to reach the maximum hydrogen generation rate. At a flow rate of 25 mL min−1 it took around 45 min to reach to maximum hydrogen generation rate, while at a flow rate of 75 mL

• maximum hydrogen generation rate was 1.5 times higher at 740 rpm than at 430 rpm. This gives evidence that increased convection improves the mass transfer of generated hydrogen from the liquid phase to the gas phase or even directly from the catalyst to the gas phase. This is in line with the measured

Facile access to pyridinium-based bent aromatic amphiphiles: nonionic surface modification of nanocarbons in water

• Lorenzo Catti,
• Shinji Aoyama and
• Michito Yoshizawa

Beilstein J. Org. Chem. 2024, 20, 32–40, doi:10.3762/bjoc.20.5

• -dibromopyridine. Negishi cross-coupling with 9-anthrylzinc chloride in the presence of PdCl2(PhCN)2/P(t-Bu)3 as catalyst afforded the common precursor 3,5-dianthrylpyridine (prePA), a simple yet novel bent building block, in 81% yield. For the synthesis of the methyl derivative, prePA was N-alkylated with excess

Synthesis of N-acyl carbazoles, phenoxazines and acridines from cyclic diaryliodonium salts

• Nils Clamor,
• Mattis Damrath,
• Thomas J. Kuczmera,
• Daniel Duvinage and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 12–16, doi:10.3762/bjoc.20.2

• turnover of the desired reaction [35]. To mitigate this, using silver salts as iodide scavengers in the reaction was attempted but yielded none of the desired product (Table 1, entry 2). DMF as a solvent lowered the yield to 16% (Table 1, entry 3). Switching the catalyst system to Cu(OTf)2/glyme gave a

• significantly higher yield of 33% (Table 1, entry 4). Increasing the amount of iodolium salt to 1.5 equivalents yielded 2a in 42% (Table 1, entry 5). Further increasing the amount of 1a to 2 equivalents raised the yield only slightly (Table 1, entry 6), while finally exchanging the catalyst to CuI/diglyme at 15

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• alkynes was studied in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF4) adding boron trifluoride diethyl etherate (BF3·Et2O) as catalyst. Different ionic liquids were used, varying the cation or the anion, in order to identify the best one, in terms of both efficiency and reduced

• 1881, Kucherov identified mercury(II) salts in sulfuric acid as efficient promoters of the hydration of alkynes and this catalyst system has found applications in industrial scale synthesis [10]. However, the toxicity and the environmental issues associated with the use of mercury-based compounds have

• examples of the hydration reaction of alkynes carried out in ILs. In one case, a dicationic IL, containing sulfuric acid as catalyst, was used as reaction medium to carry out the hydration of different alkynes under mild conditions (40–60 °C, 0.5–1 h) [84]. In a second case, different Brønsted acid ionic

Anion–π catalysis on carbon allotropes

• M. Ángeles Gutiérrez López,
• Mei-Ling Tan,
• Giacomo Renno,
• Augustina Jozeliūnaitė,
• J. Jonathan Nué-Martinez,
• Javier Lopez-Andarias,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140

• because it took some time to find the benchmark reaction needed to develop the catalysts (Figure 2) [2]. With this operational enolate chemistry in hand, it quickly became clear that increasing π acidity at the same time decreases the stability of the catalyst [3][4][5]. This suggested that induced rather

• catalyst 21 was applied to other reactions. Diels–Alder reactions are of special interest for anion–π catalysis because of the promise to accelerate an intrinsically disfavored but relevant pathway, like in the benchmark enolate addition (Figure 2) [62]. Namely, in solution, the endo transition state VI is

• product 26 and exo product 27 [64][65][66]. With the less powerful fullerene catalyst 14, the increase of the exo/endo selectivity compared to the fullerene-free control 12, i.e., exo/endo14/12 = 1.1, was negligible [12]. With the best fullerene catalyst 21, the presence of the fullerene made the

N-Boc-α-diazo glutarimide as efficient reagent for assembling N-heterocycle-glutarimide diads via Rh(II)-catalyzed N–H insertion reaction

• Grigory Kantin,
• Pavel Golubev,
• Alexander Sapegin,
• Alexander Bunev and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 1841–1848, doi:10.3762/bjoc.19.136

• tetrazoles, had not been previously utilized in the CRBN ligands design. Catalytic decomposition reactions of diazo compound 5 with NH-heterocycles were conducted in a dry DCM solution using dirhodium espinoate (Rh2(esp)2, 0.06–0.18 mol %). The Rh2(esp)2 catalyst was selected for its excellent versatility

• and efficiency in various XH insertion reactions [27][28][29]. In many cases (e.g., indoles, indazoles, benzotriazoles, tetrazoles, Scheme 3) the reaction progressed expeditiously (as indicated by gas evolution upon adding diazo reagent to the mixture of NH-substrate and catalyst) and was completed in

• ), up to 2–3 days, along with the addition of an extra portion or two of catalyst to complete the reaction. Furthermore, the yields of the NH-insertion products in the latter reactions were moderate or low (see 6h, 6r, 6s, Scheme 3). It should be noted that we have also tested some Cu(II) catalysts (Cu

Substituent-controlled construction of A₄B₂-hexaphyrins and A₃B-porphyrins: a mechanistic evaluation

• Seda Cinar,
• Dilek Isik Tasgin and
• Canan Unaleroglu

Beilstein J. Org. Chem. 2023, 19, 1832–1840, doi:10.3762/bjoc.19.135

• , Central Campus, 06790 Etimesgut, Ankara, Turkey 10.3762/bjoc.19.135 Abstract A substituent-dependent construction of novel A3B-porphyrins along with A4B2-hexaphyrins was realized by the reactions of N-tosylimines and meso-aryl-substituted tripyrranes in the presence of Cu(OTf)2 as the catalyst. The

A novel recyclable organocatalyst for the gram-scale enantioselective synthesis of (S)-baclofen

• Gyula Dargó,
• Dóra Erdélyi,
• Balázs Molnár,
• Péter Kisszékelyi,
• Zsófia Garádi and
• József Kupai

Beilstein J. Org. Chem. 2023, 19, 1811–1824, doi:10.3762/bjoc.19.133

• , application, and recycling of a new lipophilic cinchona squaramide organocatalyst. The synthesized lipophilic organocatalyst was applied in Michael additions. The catalyst was utilized to promote the Michael addition of cyclohexyl Meldrum’s acid to 4-chloro-trans-β-nitrostyrene (quantitative yield, up to 96

• % ee). Moreover, 1 mol % of the catalyst was feasible to conduct the gram-scale preparation of baclofen precursor (89% yield, 96% ee). Finally, thanks to the lipophilic character of the catalyst, it was easily recycled after the reaction by replacing the non-polar reaction solvent with a polar solvent

• , acetonitrile, with 91–100% efficiency, and the catalyst was reused in five reaction cycles without the loss of activity and selectivity. Keywords: baclofen; catalyst recovery; lipophilic cinchona squaramide; organocatalysis; stereoselective catalysis; Introduction In today’s chemical industry, catalytic

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• decarboxylative alkylation reaction that was facilitated by the synergistic action of a cost-effective and easily accessible NaI/PPh3 catalyst system (Scheme 1). This system offered an alternative to the use of precious metals or complex organic dyes as catalysts. The developed NaI/PPh3-based system not only

• , resulting in good to excellent yields and enantioselectivity. This groundbreaking work opened up new possibilities for the practical application of photoredox catalysis in large-scale industrial processes, as it provided a more accessible and cost-effective catalyst system that could be readily utilized for

• novel metallaphotoredox catalysis by combining the NaI/PPh3 photoredox catalyst with a Cu(I) catalyst to accomplish diverse C–O/N cross-couplings of alkyl N-hydroxyphthalimide esters 3 with various phenols/secondary amines 30 (Scheme 13) [24]. It was anticipated the utilization of computational methods

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• ) [30][31], metal-ion template (coordination bonds [22][32], ion-dipol [16], donor–acceptor (charge transfer, π–π stacking) [30][33], and oligoamide macrocycle-hydrogen acceptors (hydrogen bonding) [20][34]. In active-metal template methods (Figure 1) the metal ion acts both as template and catalyst for

• obtained by CuAAC in the presence of CuCl(SIMes)(4,7-diclorophenantroline) as catalyst, with very good yields. Next, we set to study the ability of compound 6 to form copper(I) complexes able to act as active-metal templates for [2]rotaxane synthesis. Therefore, complexation studies of 6 with CuCl(SIMes

• . Synthesis of the key intermediates 6 and 8 and of the reference macrocycle M1. Synthesis of [2]rotaxanes R1 and R2. Supporting Information Supporting Information File 18: Copies of NMR and HRMS spectra. Acknowledgements We thank Dr. Arnaud Gautier for providing us the catalyst used in CuAAC reaction and

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• concentration of this greenhouse gas by upcycling. Selectivity towards CO2-reduction products is highly desirable, although it can be challenging to achieve since the metal-hydrides formation is sometimes favored and leads to H2 evolution. In this work, we designed a cobalt-based catalyst, and we present herein

• purpose, three main components are needed: a photosensitizer (PS), which acts like a light-antennae harvesting system in natural photosynthesis, a catalyst (Cat.), reacting directly with CO2 after being reduced, and a sacrificial electron donor (SeD). When the involved (photo)catalysts are homogeneous

• ) intermediate could be favored concerning the formation of the CO2 adduct with the reduced metal center. Thus, besides the development of novel efficient catalysts, different strategies have been pursued to switch the catalyst selectivity towards carbon products [4][5]. Generally, scientists can interplay by

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• mmol, 0.226 g) and 2-hydroxy-3-methylbenzaldehyde (MBA, 1.0 mmol, 0.136 g), for hdz-CH3, or 2-hydroxy-3-nitrobenzaldehyde (NBA, 1.0 mmol, 0.167 g), for hdz-NO2, in 20 mL ethanol (Scheme 2). One drop of concentrated HCl was added to the mixture as a catalyst. After stirring at 50 °C for 4 h, the mixture

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• ) [70]. We expected that using olefinic oxindoles 14 as alkenes for the [3 + 2] cycloaddition could afford spirooxindole-pyrrolizidines. The method development revealed that recyclable zeolite HY acid is a good catalyst for the cycloaddition [70]. Thus, the zeolite HY-catalyzed reaction of glycine with

• (Scheme 12). Our next goal was to convert the stepwise reaction process into a one-pot synthesis. After optimizing the reaction conditions, a one-pot two-step reaction was developed by the reaction of 2-azidobenzaldehydes, 2-substituted amino acids and maleimides with AcOH as a catalyst in MeCN at 110 °C

• -aminoisobutyric acid, phenylglycine and valine with Ph or iPr groups could also be used for the synthesis of the monocycloaddition products for the post-condensation reactions. It is worth noting that in the one-pot synthesis involving an intramolecular click reaction, no Cu catalyst was used. A similar reaction

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• synthesis of these compounds involved the condensation of a meso-disubstituted dipyrromethane with diamines incorporating the crown ether/azacrown segment in the presence of boron trifluoride diethyl etherate as a catalyst [66]. The treatment of compound 16 with potassium hydride yielded 16-K2, a suitable

Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

• Aaron H. Shoemaker,
• Elizabeth A. Foker,
• Elena P. Uttaro,
• Sarah K. Beitel and
• Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

• vast body of knowledge built from many synthetic campaigns towards the Strychnos alkaloids [15]. Several combinations of palladium catalyst, base, and other additives were applied to our system (see Table 1, entries 1–4). Reaction conditions such as those deployed to great effect by Rawal [16] (Table 1

• , entry 2) and Vanderwal [17] (Table 1, entry 3) in the synthesis of other bridged azapolycycles gave poor yields when applied to vinyl bromide 7. The best result was obtained using the combination of Pd(PPh3)4, K2CO3, and proton sponge in refluxing toluene [18][19]. Although this catalyst system proved

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• with the earlier ATRP techniques (normal ATRP [41], reverse ATRP [45], SR&NI ATRP [46], and AGET ATRP [47]), the recently proposed ATRP techniques (ICAR ATRP [48], ARGET ATRP [49], SARA ATRP [50], eATRP [51][52], photoATRP [53][54], and ultrasonic ATRP [55]) require a much lower catalyst dosage, even

• photoredox catalyst mediated by light to overcome the challenge of metal contamination in the precipitated polymers [58]. After the ATRP reaction, a reactive chain end retains as a stable alkyl halide moiety. Therefore, ATRP is particularly suitable for the synthesis of polymers with complex architectures

• catalyst to produce radicals at the 2- and 5-positions of thiophene and synthesized four types of poly(3-alkylthiophene)s (PATs) with different linking ways (Scheme 10). 2.2 Polymerization by thiol–ene chemistry The thiol–ene reaction (also called alkene hydrothiolation) is the anti-Markovnikov addition of

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• -substituted triazole 3’a (entry 1, Table 1), in 21% yield, using NiCl2(PCy3)2 as a catalyst and K3PO4 as a base. A methyl handle on the gem-difluoroalkene 1 was used to aid in 1H NMR analysis. The gem-difluoroalkenes were synthesized in one step using sodium 2-chloro-2,2-difluoroacetate and triphenylphosphine

• -difluoroalkene and its existence in the vapor phase over the course of the reaction to facilitate reaction with the remainder of the azide. With the information on the temperature and time in hand, we next screened different bases (NaH, Cs2CO3, and LiHMDS) with the NiCl2(dppp)2 catalyst, which resulted in

• % (Table 1, entry 11). To determine the role of the catalyst, we next ran the reaction without catalyst using 0.4 equiv of LiHMDS at 50 °C, which afforded the product in 31% yield (Table 1, entry 12). In order to ascertain whether a higher temperature would improve the yield, we increased the temperature

Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

• scaffolds is the introduction of a benzylidene moiety on C5 via a Knoevenagel reaction. Here, a facile synthesis of 5-arylidenerhodanines via a Knoevenagel reaction in an ʟ-proline-based deep eutectic solvent (DES) is reported. This method is fast (1 h at 60 °C), easy, catalyst-free and sustainable as no

• Knoevenagel condensation of rhodanine with different aldehydes [3]. The reactions were performed in ChCl/urea (1:2) at 90 °C, without needing a catalyst and the products were obtained in low to good yields (10–78%). On another hand, ʟ-proline is well known as an organocatalyst and its use in aldol and

•  2, entry 5). This observation demonstrates the positive role of proline on the reaction mechanism but clearly indicates that it is not sufficient. In fact, the exact role of DES in this reaction is still not clear as ʟ-proline may act as a catalyst via an iminium pathway as previously described [21

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• -coupling, and direct sulfenylation reactions, which are classified into three categories: sulfenylation catalyzed by i) transition metal catalysts, ii) organocompound catalysts, and iii) catalyst-free sulfenylation. Review Sulfenylation of organic compounds by N-(sulfenyl)succinimides/phthalimides Metal

• succeeded in synthesizing various diaryl(alkyl) sulfides 5 through the sulfenylation of unactivated arenes 4 with an electrophilic sulfur reagent in the presence of a palladium catalyst (Scheme 3) [45]. In the second phase, dibenzothiophene derivatives 6 were obtained via subsequent intramolecular arylation

• of aryl sulfides by using the catalyst and the base. A catalytic cycle is shown in Scheme 4. Firstly, electrophilic Pd(TFA)2 generated from Pd(OAc)2 and TFA, which (by C–H functionalization of arene 4) led to intermediate II. Oxidative insertion of intermediate II into the N–S bond of 1 afforded

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• carbonyl compounds to provide the corresponding zinc enolates (Scheme 1) [1][2]. While simple, this reaction offers attractive features: 1) it proceeds under mild conditions in the absence of any transition-metal catalyst; 2) the 1,4-addition step can be combined with condensation reactions of the zinc

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• addition; [3 + 2] cycloaddition reaction; hydrosilylation reaction; N-heterocyclic carbenes; NHC–Cu complexes; NHC–Cu complexes as catalyst; Introduction N-Heterocyclic carbenes (NHCs) are a neutral species having the carbene carbon atom as a part of the nitrogen heterocyclic ring. The transient

• having a triisopropoxy(propyl)silyl ((-CH2)3Si(OiPr)3) substituent on the imidazole ring through in situ transmetallation. One of these complexes, 78a, was successfully anchored on mesoporous silica MCM-41 to afford a new heterogeneous catalyst (Scheme 27). Both compounds were subsequently used as

• alkyl halides (Scheme 38) [53]. Carbonylative silylation of unactivated alkyl halides was achieved by using the commercially available Si nucleophile PhMe2Si-Bpin in the presence of IPrCuCl complex 106 as catalyst (Scheme 38). This allowed to obtain alkyl-substituted acylsilanes 107 in high yields from

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• reaction time and the fairly high amount of catalyst employed. As an alternative method, which should be more chemoselective, we examined the reduction with samarium diiodide [60]. This versatile one-electron transfer reagent is known to cleave N–O bonds with high selectivity [61][62] and was applied

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• of H2O were added to the reaction mixture [40] (Table 1, entry 6), but the addition of more water did not improve the reaction efficiency further (Table 1, entry 7). The structure of nickel catalysts played a significant role in the reaction efficiency. Switching the Ni catalyst to NiCl2(dtbbpy

• light-induced charge transfer event to give trifluoroethoxyl radical B, followed by a 1,2-hydrogen atom transfer (HAT), producing the stable radical C. For the nickel cycle, it is initiated by oxidative addition of Ni(0) catalyst E to acyl electrophile D formed in situ from carboxylic acid 1 with

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• involves a hydride abstraction from the benzylic site of isochroman to generate a cationic species A, whereas the malonate is activated by the In/Cu catalyst (B). Subsequently, the coupling of the two intermediates yields the desired product and regenerates the catalyst. Alternatively, In(III) may be

• involved in the activation of DDQ by coordinating the carbonyl oxygen atom which leads to an increase in the oxidation activity of DDQ. Subsequently, Li et al. improved the above method, using a mixture of indium and copper salts as a catalyst, NHPI (N-hydroxyphthalimide) as a co-catalyst to achieve the

• triggers the whole coupling reaction. The potential application of NHIP as a catalyst for oxidative coupling reactions with oxygen as a terminal oxidant was explored. In 2011, Garcia-Mancheño et al. developed a Cu-catalyzed CDC of cyclic benzyl ethers 10 with aliphatic or α,β-unsaturated aldehydes 13 or 14