2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• molecules have been examined. Additionally, theoretical studies based on density functional theory (DFT/B3LYP/6-31G(d)) were carried out. Keywords: alkynes; catalysis; cross-coupling; heterocycles; palladium; Introduction The development and design of small π-conjugated molecules have attracted increasing

• catalysis. With this precursor in hand, we intended to expand the π-conjugation by introducing two arylethynyl groups by Sonogashira reactions [66][67][68][69]. For the optimization, we studied the reaction of 2 with phenylacetylene (3a) and we obtained the desired product 4a in up to 72% as best yield

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• preparation of 1,4,5-trisubstituted 1,2,3-triazoles have gained much attention in triazole chemistry. Generally, two protocols for the synthesis of this type of triazole derivatives could be mentioned (metal or metal-free catalysis). Contrary to sporadic attempts [34], there is no detailed, systematic, and

• environmental catalysis area. A metal-free protocol has been developed for the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles 3 from the reaction between α-bromo-β-alkylacroleins and α-bromo-β-phenylacroleins 1 and organic azides 2 in chloroform at room temperature (Scheme 2). A low to moderate yield of

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• nucleophiles, along with transition-metal catalysis, in olefin alkylation reactions [18][19][20][21]. Apart from the early examples of olefin functionalization with transition metals, such as the well-known ethylene oxidation catalyzed by Pd(II) (the Wacker reaction) [23][24], the use of carbon nucleophiles in

• hampered the development of more general catalytic hydrofunctionalization methodologies until Widenhoefer’s work in 2001 [25]. Based on previous works that had demonstrated the addition of stabilized carbanions [26][27] and enol silyl ethers [28] to olefins under stoichiometric Pd catalysis, the authors

• nucleophilic attack on the metal-complexed olefin (see Scheme 3, intermediate A). Taking advantage of HCl as an additive (or generated in situ by silyl chloride hydrolysis), Widenhoefer described the intramolecular hydroalkylation of even less reactive alkenyl ketones 4 under Pd(II) catalysis, with minor

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

• manufacture functional soft materials will be of high interest in near future by the means of catalysis and agricultural delivery. Keywords: hydrophobic hydrogel; photoactive hydrogels; photomodification; pore modification; soft materials; Introduction Popularity of hydrogels arises from their structural

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

• reactor is, in certain instances, indicated to give rise to superior reaction kinetics [79]. It is also easy to create staged temperature gradients to compensate for changes in reaction kinetics based upon concentration or complicating effects such as product derived auto-catalysis. The use of immobilised

• often a work-up procedure meaning that this approach is very accommodating of direct telescoping into further reaction steps and reactors. So far, heterogeneous catalysis of aldol reactions in flow has been mostly geared towards achieving transformations with high enantioselectivity, towards decreasing

• -bed microreactor was found to possess good long-term stability and could be used for the catalysis of a range of aldol reactions, one example is given in Scheme 8. Conveniently, just one starting material stock solution was all that was necessary, meaning that 4-chlorobenzaldehyde (64) could be

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

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• with sodium tetraarylboronates 64 was found to proceed with high diastereoselectivity under rhodium catalysis. Reddy and co-workers applied this methodology to the synthesis of 2-substituted pyrrolidines 66 [95]. The arylation of chlorinated imine (RS)-63 was performed with 2 mol % of an air-stable

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

• given combination of enone and arylboronic acid. Keywords: asymmetric reaction; boronic acid; conjugated enones; chromones; enantioselective catalysis; Michael addition; Pd complexes; Introduction The asymmetric 1,4-addition of arylboronic acids to conjugated cyclic enones and chromones is a very

• ]. Evaluation of current state and outlook Asymmetric addition reactions to enones have so far been described in the literature in connection with catalysis. The catalyst is usually a complex of a transition metal with a suitable ligand. However, metal-free catalysis is also known [64]. Among the most

• addition reaction of phenylboronic acid to 3-methyl-2-cyclohexenone and affording the product in a low yield and moderate enantioselectivity (36%; 85% ee; Scheme 26) [20]. Palladium-based catalysis provides better results in this area. Up to now, asymmetric addition reactions to sterically hindered enones

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• substituted cyanoguanidine as the intermediate. Practically, very little improvement was made over synthetic procedures reported 50 years ago. To the best of our knowledge modern activations such as Lewis acid-promoted additions, catalysis or microwave irradiation have never been tried for this reaction

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• work focuses on a metal-free approach for the synthesis of benzofuropyridine analogues. Results and Discussion The synthesis of target compound 13 involved three steps (Scheme 1). C–H Arylation, as needed in the first step, is usually carried out using transition metal catalysis [31]. Furthermore

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• )-modified oligonucleotides was first described in 1991 by the Caruthers group [84]. Typically, each 2'-deoxynucleoside 3'-phosphorothioamidite is prepared by phosphitylating the protected nucleosides with tris(pyrrolidino)phosphine under tetrazole catalysis, followed by immediate treatment with

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• study if and how the product ee declines at high conversion. Keywords: enantiomeric excess; enzyme; kinetic mechanisms; kinetic parameters; prochiral; Introduction There is great interest in using enzymatic catalysis in the synthesis of homochiral molecules. An early approach was to use

Chiral isothiourea-catalyzed kinetic resolution of 4-hydroxy[2.2]paracyclophane

• David Weinzierl and
• Mario Waser

Beilstein J. Org. Chem. 2021, 17, 800–804, doi:10.3762/bjoc.17.68

• -catalyzed acylation with isobutyric anhydride. This protocol allows for a reasonable synthetically useful s-factor of 20 and provides a novel entry to obtain this interesting planar chiral motive in an enantioenriched manner. Keywords: acylation; kinetic resolution; nucleophilic catalysis; paracyclophanes

• polymer chemistry [1][2][7][8][9], these planar chiral molecules have been very successfully used in asymmetric catalysis [3][4][10][11][12]. Accordingly, the development of methods for the asymmetric synthesis of enantiomerically pure, or at least enantiomerically enriched, derivatives that can be

• utilized as building blocks for more demanding ligands and catalysts became a task of high importance. Thus, several strategies to access enantioenriched [2.2]paracyclophanes have been reported, either relying on classical resolution approaches or, more recently, making use of asymmetric catalysis to carry

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

• the subsequent reaction (Scheme 28). On account of a wide range of substrates and functional group compatibility, this protocol can be exploited to assemble various β-trifluoromethylated alkynes by three-component reaction without transition-metal catalysis. In 2018, Xu and colleagues [48] proposed

• -protected amines, have been efficiently transformed to suitable pinacol boronic esters. This simple operation without transition-metal catalysis will be widely promoted in the synthesis of important boron-containing molecules in medicine and biology. In 2019, Aggarwal and colleagues [55] proposed that the

• widespread presence in pharmaceutical-, agrochemical-, and materials sciences [73][74][75]. At present, most of the C–N-bonding reactions require transition-metal catalysis, and the reaction conditions are more stringent; however, the EDA-complex pathway proceeds under mild, catalyst-free conditions

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• compounds as binucleophiles for the construction of various carbocycles, heterocycles as well as in asymmetric catalysis [44][45][46][47][48][49][50]. Our initial objective to trap the aza vinyl rhodium carbenoid using 1,3-dicarbonyl compounds to form pyrazolone was unsuccessful which instead led to the

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• bond. Usually, AAC reactions on non-terminal alkynes are performed with ruthenium catalysis [21] that determined our decision to start screening conditions using the chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium(II) complex ((Cp)Ru(PPh3)2Cl) as catalyst. However, carrying out the reaction

• complex scaffold in just two steps. Unusually, the azide–alkyne cycloaddition for both terminal and non-terminal alkynes was effective under catalyst-free conditions while normally for non-terminal alkynes a ruthenium-based catalysis is required. Using the developed method, a library of 22 target

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• . Catalysis is the next area that is gaining an ever-increasing practical focus in the studies on the use of C60 and fullerene-containing materials [51]. A comparative analysis of the activity of fullerene-containing compounds and noble metals as dehydrogenation catalysts allows to consider the former as

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

• processes, acid–base treatments as well as the production of fuels are not discussed, nor are the methods for the further upgrade of the depolymerisation products. Keywords: catalysis; depolymerisation; plastic; recycling; sustainable; Review 1. Introduction In a circular-economy perspective, wastes are

• [125][126]. 3. Selective depolymerisation of plastics via metal catalysis Research in depolymerisation of plastics by artificial metal catalysts is relatively recent as most of the earliest studies are related to biocatalytic systems. Metal salts are the conventional catalysts for these processes

• 3), whilst a high surface area around 150 m2⋅g−1 was proposed to increase the number of exposed sites [214]. Zn@TiNT afforded BHET in 87% yield at 196 °C reaction temperature. TiNT have received significant general interest in heterogeneous catalysis because of the better active-site-accessibility

Designed whole-cell-catalysis-assisted synthesis of 9,11-secosterols

• Marek Kõllo,
• Marje Kasari,
• Villu Kasari,
• Tõnis Pehk,
• Ivar Järving,
• Margus Lopp,
• Arvi Jõers and
• Tõnis Kanger

Beilstein J. Org. Chem. 2021, 17, 581–588, doi:10.3762/bjoc.17.52

• toxic oxidants. Keywords: chemoenzymatic synthesis; cortisol; hydroxylation; secosterol; whole-cell catalysis; Introduction Developments in the chemistry of steroids have stimulated extensive research interest in the exploration of new synthetic methods since the 1960s. Advances in synthetic biology

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• order to avoid the relatively long synthesis of the precursors we tried to change Br for another leaving group Y (Scheme 4). First, we prepared 3-chlorooxindole (1f) which is available from β-nitrostyrene and acetyl chloride under FeCl3 catalysis [41]. Unfortunately, the Eschenmoser coupling reaction

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

• Lucía Rossi-Fernández,
• Viviana Dorn and
• Gabriel Radivoy

Beilstein J. Org. Chem. 2021, 17, 519–526, doi:10.3762/bjoc.17.46

• heterogeneous catalysts [27] that are wide in substrate scope, active enough and highly selective. As part of our continuing interest in the development of new synthetic methodologies based on the use of catalysis by non-noble transition metal nanoparticles (MNPs) for their application in a wide range of

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• %) catalyst loading. Selected enantiomerically enriched sulfa-Michael addition products were subjected to oxidation to obtain the corresponding sulfones. Keywords: asymmetric synthesis; bifunctional catalysis; cinchona alkaloids; organocatalysis; sulfa-Michael reaction; Introduction Derivatives of the

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• insertion reactions. The reaction of the N-protected amino acids 209 and 210 with diethyl 1-diazo-2,2,2-trifluoroethylphosphonate (211) gave rise to the trifluoromethyl-containing phosphonodepsipeptides 212 and 213 with C-1-hydroxyalkylphosphonic acids in good yields under the catalysis of dirhodium

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• beneficial effects generally resulting from the introduction of these fluorinated motifs [13], also participated in this development. These fluorine effects are nowadays remarkably established in many domains, including medicinal, organic, and organometallic chemistry, catalysis, chemical biology, and

• a longer reaction time, allenes 127 undergo a subsequent intramolecular hydroarylation reaction leading to indenes 128. The authors suggested the formation of FeCl3–HFIP complexes being involved in a Lewis acid-assisted Brønsted acid catalysis. The CF3-substituted propargyl alcohol 129 was found to

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• were increased when potassium fluoride and 18-crown-6 were added to the reaction mixture [20]. Dehydrohalogenation of dichlorodifluoromethane under phase-transfer catalysis: Difluorocarbene can be generated from chlorodifluoromethane by phase-transfer catalysis (PTC) through the reaction with NaOH or

• -difluorocyclopropanes in the synthesis of fluoroalkenyl-substituted compounds (monofluoroalkenes) have been actively studied. Great opportunities exist for the use of transition metal catalysis. The catalytic hydrogenolysis of 1,1-difluoro-3-methyl-2-phenylcyclopropane (151) led to the regioselective C2–C3 distal bond

• reaction of 2-(2,2-difluorocyclopropyl)naphthalene (167) with sodium arylsulfinates 168 under palladium catalysis afforded the 2-fluoroallylic sulfones 166 in moderate to good yields with (Z)-selectivity. This method showed a good compatibility with a broad range of substrates and substituents. As