Green synthesis of C5–C6-unsubstituted 1,4-DHP scaffolds using an efficient Ni–chitosan nanocatalyst under ultrasonic conditions

• Soumyadip Basu,
• Sauvik Chatterjee,
• Suman Ray,
• Suvendu Maity,
• Prasanta Ghosh,
• Asim Bhaumik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 133–142, doi:10.3762/bjoc.18.14

• (NPs) and therefore automatically increases the dispersibility of the catalyst throughout the medium, resulting in a higher catalytic activity [23]. 1,4-DHPs are considered one of the most useful molecular scaffolds in medicinal chemistry. The scaffold is the main constituent of several crucial drugs

• up to 97% using an external magnet. In a series of five reactions, the catalyst was used repeatedly without significant decrease in catalytic activity (Figure 7). The slight reduction of the yield in later reactions may have been a result of the loss of catalyst in the recycling process. Comparison

• to five consecutive reactions without significant reduction of catalytic activity. To the best of our knowledge, no previous work is known using a Ni–chitosan nanocatalyst for the synthesis of C5–C6-unsubstituted 1,4-DHPs. Experimental Materials and instrumentation All starting materials were

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• . It was concluded that the catalytic activity of the MDO was the result of the cooperative action of both constituents. Several examples of such MDOs are included in the paper. The reported yield varies from 56–90% with excellent ee ≈ 99% in all cases. 1.2. Reactions catalyzed by chiral squaramide

Targeting active site residues and structural anchoring positions in terpene synthases

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 2441–2449, doi:10.3762/bjoc.17.161

• are otherwise highly conserved. Site-directed mutagenesis experiments for these residues are reported that showed different effects, resulting in some cases in an improved catalytic activity, but in other cases in a loss of enzyme function. For other enzyme variants a functional switch was observed

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• -metathesis (ROCM) have found high utility in the creation of C=C bonds and in the synthesis of a number of organic molecules, functionalized scaffolds or various building blocks. The efficient catalytic activity and remarkable functional group tolerance of commercially available versatile Ru-based olefin

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

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• highlight that solvent-free conditions are particularly effective and allow for reducing the catalyst loading by the factor of 10, thereby obtaining a higher share of 3dia and full conversion towards 3dic. Interestingly, the catalytic activity of TPP in reactions with 3 as the Michael acceptor is only

• for reacting weak Michael acceptors and/or less acidic alcohols. Phosphine loadings of only 1 mol % with respect to the Michael acceptor are in many cases sufficient to provide a full conversion within 24 h at room temperature. With good Michael acceptors and/or acidic alcohols the catalytic activity

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

• pores is responsible for the main catalytic activity, such as in carbonaceous materials [47][48]. When a network with full functionality cannot be formed easily, one can form a rigid neutral host and modify the pores subsequently. Herein, the nanoporous system is magnified to macropores in hydrogel

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

• ). Traditional g-C3N4 exhibited a low catalytic activity for this transformation (Table 1, entry 6). Switching from CN-K to a homogeneous organo photocatalyst such as eosin Y and 4CzIPN, led to lower yields of the desired product (Table 1, entries 7 and 8). The expensive Ru/Ir-based metal complexes gave similar

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• increased the catalytic activity and allowed to run the reaction at a lower temperature [48]. This can be very useful for substrates that can react with traces of Pd(0) that are formed by minor side reactions. The authors suspected that hexafluorophosphate anions stabilize the cationic Pd species and result

• achieving a higher ee, however, it also caused a faster loss of catalytic activity. Later in 2020, Zhou et al. used an analogous heterogeneous system as O’Reilly (cf. Table 28) [56][58]. A RAFT polymerisation reaction, in this case, led to a polymeric backbone with terminal catalytic centres [58] (Scheme 20

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

• synthetic method for the highly selective synthesis of the (E)- or (Z)-isomers is strongly desired [27][28][29][30]. Furthermore, since it was reported that the introduction of a substituent into the ethylene moiety has a great effect on the catalytic activity [31], it is considered important to synthesize

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• (dicyclophosphino)ethane) showed minimal improvements compared to the chloride salt catalyst [205]. The use of transition metal-substituted polyoxometallates (POMs), of the general formula K6SiW11MO39(H2O) (M = Zn2+, Mn2+, Co2+, Cu2+, Ni2+) [206][207], was also investigated [208]. The catalytic activity was found

• compared to 2D materials, thanks to a typical 8–16 nm outer diameter tubular morphology [215][216] and the potential for facile metal doping via ion-exchange of the solid support [217][218]. Lewis acid-type catalytic activity was also postulated for γ-Fe2O3 NPs, which provided BHET in 90% yield at 300 °C

• [ZnCl3] (bmim = 1-butyl-3-methylimidazolium, Table 4, entry 2) [228] were recently studied, showing higher catalytic activity compared to metal-free ionic liquids (i.e., bmim chloride), the conventional catalysts (i.e., ZnCl2, Zn(OAc)2) or the analogous Mn, Co and Cu ionic liquids. Typically, 80–85% BHET

Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• -membered chelate rings. The testing of the catalytic ability of the cyclam-based N,N,N,N-Au(III) complexes demonstrated high catalytic activity of some complexes in selected test reactions (full conversion in 1–24 h, 62–97% product yields). Keywords: Au(III); carboalkoxylation; coordination studies

• , due to sample decomposition. Attempts to obtain crystals for X-ray analysis by slow diffusion of n-pentane into a DCM solution of the complexes were unsuccessful. Catalytic activity For evaluation of the catalytic ability of the new Au(III) complexes, alkyne carboalkoxylation [47][48] and

• . Evaluation of complex 6b-Au(III) in both reactions, revealed a large difference in catalytic activity and complex stability between the structurally similar 6a-Au(III) and 6b-Au(III) cyclam complexes, with a cyclohexyl and a diphenyl-C2 bridge between the nitrogens, respectively. In both test reactions, an

Direct synthesis of anomeric tetrazolyl iminosugars from sugar-derived lactams

• Michał M. Więcław and
• Bartłomiej Furman

Beilstein J. Org. Chem. 2021, 17, 115–123, doi:10.3762/bjoc.17.12

• of this research we have developed a methodology for the synthesis of sugar-derived α-tetrazolylamines. Such compounds – incorporating both iminosugar and tetrazole fragments – are particularly interesting, thanks to the well-known biological and catalytic activity of these moieties. This work is the

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• -fluorovinylphosphonates under mild conditions. First, we examined the catalytic activity of various transition metal catalysts, including Au, Ag, Cu, Rh, and Pd complexes (Supporting Information File 1). Among these metal salts, silver salts, especially AgOAc, were the most effective catalysts for generating the desired

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• a robust supporting material to immobilize a copper species. The so-obtained catalyst was characterized by many physicochemical methods including FTIR, EA, FSEM, FTEM, XPS, and TG. This catalyst exhibited excellent catalytic activity in the synthesis of nitrogen-containing heterocycles such as

• spectra were further recorded, and the results confirmed the presence of Cu+ at ≈570 eV, while Cu0 at 565.6 eV [29][30][31], meaning that Cu2+ species were partially reduced during the course of immobilization. Catalytic activity of the catalysts With the catalysts in hand, we investigated their catalytic

• were formed (Table 1, entry 1). After screening different kind of solvents (Table 1, entries 2–8) at 60 °C, EtOH was found to be the best one, and the target product 4a was obtained in 86% yield (Table 1, entry 8). The referential catalysts LS-FM-Cu and Resin-Cu showed inferior catalytic activity for

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• innovative catch–release system with multiple functions combined the ON/OFF-adjustment of silver(I) catalysis and fluorescence monitoring [59]. Actually, the ratiometric luminescence response allowed the exact monitoring of the catalytic activity. In the initial incomplete self-sorting (state SelfSORT-I

• finding suggested that the catalytic activity in SelfSORT-II was reduced to roughly half of the initial activity in SelfSORT-I. Finally, the addition of two equiv of copper(I) ions generated SelfSORT-III where no additional product was afforded, indicating an OFF state of the catalytic machinery. To

• catalytic activity. In sum, this study demonstrated partial and full release/binding of the organocatalyst 75 during the walking of the biped. Rather recently, the Schmittel group described a precise intermolecular communication system, in which multiple self-sorting steps set up a catalytic AND gate

Palladium nanoparticles supported on chitin-based nanomaterials as heterogeneous catalysts for the Heck coupling reaction

• Tony Jin,
• Malickah Hicks,
• Davis Kurdyla,
• Sabahudin Hrapovic,
• Edmond Lam and
• Audrey Moores

Beilstein J. Org. Chem. 2020, 16, 2477–2483, doi:10.3762/bjoc.16.201

• deposit Pd NPs directly onto both ChNCs and ChsNCs, and the as-made heterogeneous catalysts were tested with the Heck coupling reaction as a model for catalytic activity. Findings The fabrication of ChNC and ChsNCs was conducted using a procedure previously reported by our group (Lam) (see Supporting

• system has higher catalytic activity in more benign conditions, with the Pd NP on SiO2 system yielding 92% stilbene product at 110 °C and using dimethylformamide as the solvent [23]. Other examples using carbon-based supports such as carbon spheres [24] and graphene oxide [25] also have formidable yields

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• residues were introduced instead of the diene ligands. Again helicates with a statistical distribution of chiral ligands and of the new amine ligands in the complex were investigated as catalysts. The ligands with potential catalytic activity were synthesized in a three-step approach (Scheme 4). Initially

• equivalent of 13-H2 and 5 equivalents of 2-H2, 4-H2, and 5-H2. The catalytic activity of the amine ligands was tested first by using the uncoordinated ligand 13a-H2 substituted with a N-methylethylamine moiety. The reaction was performed in DMSO-d6 due to solubility limitations of the ligand. Fast and easy

• the supposed reason for this observation. Thus, the amine ligand 13b-H2 seemed to be an appropriate component to make helicates from ligand mixtures which possess catalytic activity. Exchange of the chiral ligand 2 by other chiral ones resulted in the corresponding complexes Li4[(13b)1(4)5Ti2] and Li4

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• colorless crystals of 128. Along similar lines the crystals of 127 were achieved by following the same procedure. On the other hand, the groups of Amaya and Hirao have reported the synthesis of sumanenyl mono- and trihafnocene complexes 129 and 130, respectively, along with the catalytic activity of 129 for

• subjected 2 with an excess of t-BuLi and then quenched it with Cp*HfCl3 as displayed in Scheme 34. Furthermore, they revealed for the first time the catalytic activity of sumanene metallocene for the hydroethylation reaction of unactivated allylbenzene by treating it with AlEt3 at room temperature to

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• switch the catalytic activity of the dimethylaminopyridine (DMAP) unit. DMAP is a known catalyst in the nitroaldol (Henry) reaction. Upon coordination to the Ni2+ ion, the basicity of the pyridine lone pair is attenuated and hence the catalytic activity is reduced. Decoordination restores the catalytic

• -epoxypropane to propylene carbonate using an aluminum porphyrin and a photoresponsive ligand. The catalytic activity of the metal porphyrin depended on the axial coordination of an azostilbene and coordination of the latter ligand was controlled by photoisomerization of the stilbene unit [9]. Hecht et al

• thermal relaxation of the coordinated cis state is insignificant for our catalytic studies. Experiments using porphyrin 1 as a catalyst The Henry reaction (Scheme 2) was chosen as a model reaction to investigate the catalytic activity of porphyrin 1 in the two different switching states because the rate

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• in hydrohydrazidation reactions than the previously reported [(Ph3P)Au(NTf2)] [42]. Solvent screening: Among the solvents tested in the previous study by Rassadin, Kukushkin et al., chlorobenzene was found to be the best solvent concerning the catalytic activity [42]. However, according to the CHEM21

Synergy between supported ionic liquid-like phases and immobilized palladium N-heterocyclic carbene–phosphine complexes for the Negishi reaction under flow conditions

• Edgar Peris,
• Raúl Porcar,
• María Macia,
• Jesús Alcázar,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2020, 16, 1924–1935, doi:10.3762/bjoc.16.159

• PdII. In this way, a “cocktail” of catalytic species, including molecular complexes, clusters and nanoparticles may be responsible for the catalytic activity [15]. In a continuous system, this can be accompanied by a significant leaching of the catalytic metal. In order to avoid a loss of activity by

• kinetic plots for this model reaction are represented in Figure 1. The NHC–Pd catalyst 4a showed a rather reduced activity (less than 10% after two hours), while the catalyst bearing isopropyl moieties at the aromatic ring (4b) displayed a significant increase in the catalytic activity, reaching 67% yield

• enhanced precatalyst preparation, stabilization and initiation, PEPPSI) [23][24]. In addition to pyridine ligands, other compounds with coordinating atoms such as C, N or P have been reported to tune the catalytic activity of the NHC–Pd complexes [25][26][27][28]. Thus, a ligand containing P as the

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• , the elemental composition of the NDL catalyst was determined by EDAX analysis (Figure 6). The catalytic activity of the NDL for the synthesis of the 1,2-disubstituted benzimidazoles 3, the dihydropyrimidinones/-thiones 7, and the 2-amino-4-(hetero)aryl-3,5-dicarbonitrile-6-sulfanylpyridines 11 was

• investigated, along with other, commercially available catalysts. NDL-catalyzed synthesis of 1,2-disubtituted benzimidazoles 3 To check the catalytic activity of the NDL, initially, o-phenylenediamine (1) and benzaldehyde (2a) were chosen as model substrates to optimize the reaction conditions for the

• by comparison of the melting point and spectroscopic data with those reported. NDL-catalyzed synthesis of dihydropyrimidinones/-thiones 7 The results encouraged us to further investigate the catalytic activity of the NDL in the Biginelli reaction. To check the feasibility, a control experiment was