Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• , e.g., from the metals magnesium or zinc, (thermal) activation is required. This was demonstrated for the Reformatzky reaction (Scheme 11, case B) [53][74], in which zinc powder was mixed with MagSilicaTM and positioned inside the flow reactor. For example, 2-bromopropanoic acid ethyl ester (52) and

Mechanochemical halogenation of unsymmetrically substituted azobenzenes

• Dajana Barišić,
• Mario Pajić,
• Ivan Halasz,
• Darko Babić and
• Manda Ćurić

Beilstein J. Org. Chem. 2022, 18, 680–687, doi:10.3762/bjoc.18.69

• azobenzenes with electron-donating substituents by electrophilic activation with NXS. Halogenation of azobenzenes with electron-accepting substituents Using the optimal parameters for the mechanochemical bromination and iodination of L1 [51], we investigated the halogenation of azobenzene substrates with

• Supporting Information File 1). Compared to L1 [51], iodination of its para-halogenated derivatives resulted in lower yields of diiodinated products (Table 2, entries 9–12) since the activation/halogenation of the C–H bond occurs preferentially at the unsubstituted azobenzene phenyl ring [57]. The reactions

• dynamics of the formation of cyclopalladated intermediates In-I, LAG reactions of Pd(OAc)2 with L6–8 and TsOH were performed using 25 µL of MeCN as a liquid additive in a molar ratio of 1:1:1 (Ln/Pd(OAc)2/TsOH). In situ Raman monitoring of C–H bond activation was possible for L6 and L7, while in the case

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• decades. With the combination of C–H activation, many aminations of aryl compounds have been established [6][7][8][9][10][11][12][13][14][15][16]. However, it is necessary to introduce the directing group into the arene in most successful cases. As a good amino source, phthalimides have been widely

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

• groups or surface/volume properties for catalytic activation [4][5][6][7][8][9][10][11][12]. In the present short review, limited to discrete heteroleptic metallo-supramolecular ensembles [13][14], we will show that, in addition to the above-mentioned way, there are other diverse possibilities to profit

• ], Fujita [56], and others [57] have reported several template-free assemblies giving access to novel structures. The primary objective of these nanovessels as supramolecular catalysts is to encapsulate organic reactant/s to lower the activation barrier, thereby mimicking the functions of enzymes (without

• ]. Using addition and removal of chloride, the Mirkin group reversibly and quantitatively toggled the platinum(II)-based switch 1262+ between a homo- and heteroligated form (Figure 29) [132]. In the closed platinum(II) complex 1262+, the urea units were available for activation of butenone (127) by

Shift of the reaction equilibrium at high pressure in the continuous synthesis of neuraminic acid

• Jannis A. Reich,
• Miriam Aßmann,
• Kristin Hölting,
• Paul Bubenheim,
• Jürgen Kuballa and
• Andreas Liese

Beilstein J. Org. Chem. 2022, 18, 567–579, doi:10.3762/bjoc.18.59

• Scientific GmbH, Schwerte, Germany), and membrane filters (3 µm) (Sartorius AG, Göttingen, Germany). The carriers were equilibrated with immobilization buffer at a carrier to buffer ratio of 1:1 (w/v). For the amino methacrylate carrier (ECR8309F), a further step of activation was performed with 2

Bioinspired tetraamino-bisthiourea chiral macrocycles in catalyzing decarboxylative Mannich reactions

• Hao Guo,
• Yu-Fei Ao,
• De-Xian Wang and
• Qi-Qiang Wang

Beilstein J. Org. Chem. 2022, 18, 486–496, doi:10.3762/bjoc.18.51

• tertiary amine sites were found to be crucial for achieving efficient activation and stereocontrol. As shown in control experiments, catalysis with the acyclic analogues having the same structural motifs were non-selective. Keywords: chiral macrocycles; cooperative asymmetric catalysis; decarboxylative

• anion binding property and potent electrophilic activation ability [31][32][33][34][35][36]. To incorporate extra functionality, tertiary amine groups can be also embedded as Lewis base sites for realizing electrophilic/nucleophilic cooperative catalysis [37][38][39]. For this purpose, one kind of

• report a systematic synthesis of tetraamino-bisthiourea chiral macrocycles and their performance in catalyzing the decarboxylative Mannich addition of malonic acid half thioesters (MAHTs) to isatin-derived ketimines. The macrocycle-enabled hydrogen-bonding activation network and the associated confined

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• in electron density on the acceptor and the electron-donating power of POZ. Therefore, gradual increase of electron-donating strength brings T1 energy closer to the acceptor T1 energy and leads to a smaller EST gap. But, the activation energy Ea for the DF process, which was calculated from the

• Arrhenius plot obtained from the increase of the DF intensity against temperature, was lower for 1 (Ea = 27 meV) when compared to POZ-DBPHZ (Ea = 47 meV, Table 2) in Zeonex®. The directly determined activation energy of the D–A-type compound is half than that of the D–A–D compound, which is in contradiction

• to the ΔEST value (Table 2). If we support the observation with the DF/PF results that present a stronger TADF property for the mono-substituted derivative 1, the conclusion of misleading ΔEST comparison can be reached. To avoid confusion, a more effective way is to compare only the activation energy

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

A resorcin[4]arene hexameric capsule as a supramolecular catalyst in elimination and isomerization reactions

• Tommaso Lorenzetto,
• Fabrizio Fabris and
• Alessandro Scarso

Beilstein J. Org. Chem. 2022, 18, 337–349, doi:10.3762/bjoc.18.38

• the active site of the enzyme. Once bound, substrate activation is carried out by specific amino acid side chains that adorn the inner surface of the cavity by means of a combination of covalent and/or weak intermolecular interactions leading to the stabilization of intermediate species and transition

• evidence of the importance of an accessible cavity for the activation of the reaction after alcohol protonation. It is known that 16 behaves as a weakly acidic assembly with pKa of about 5.5 [42], while the resorcinol moiety presents a pKa of 9.15. This enhanced acidity is likely to promote the protonation

• observe activation of the reaction by the capsule. In fact, the reaction with the capsule under identical experimental conditions using 1-phenylethanol as substrate did not provide any evidence of formation of the corresponding alkene product even after 20 h at 60 °C. Secondary aliphatic alcohols can be

A Se···O bonding catalysis approach to the synthesis of calix[4]pyrroles

• Qingzhe Tong,
• Zhiguo Zhao and
• Yao Wang

Beilstein J. Org. Chem. 2022, 18, 325–330, doi:10.3762/bjoc.18.36

• investigation on using an asymmetric ketone such as pentan-2-one as a reactant showed that the reaction gave an inseparable mixture of diastereomers. Meanwhile, upon using benzaldehyde as a reactant, the reaction system was complex and there was no major product. Proposed activation mode The chalcogen bonding

• monodentate and bidentate catalysts could activate ketones. Accordingly, either a single activation or a double activation mode could be an effective driving force to promote this transformation, albeit with distinct catalytic activity. Conclusion In summary, we developed a Se···O bonding catalysis approach

• . Proposal of a Se···O bonding catalysis approach. Se···O bonding catalysis approach to the synthesis of calix[4]pyrrole 2a. Reaction scope. Proposed activation mode. Supporting Information Supporting Information File 58: Full experimental procedures and compound characterization. Acknowledgements

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• , directing groups are introduced to the substrates covalently to achieve site-selective C–H bond activation, which prospered greatly in the past decades [7][8][9]. Template regulation is also introduced to locate reactive centers in a noncovalent way through hydrogen bonding [10][11][12]. Even though

• powerful role of molecular containers to achieve precise transformation of complex molecules. Oxidation C–H bonds are ubiquitously distributed in nearly all of the organic compounds, which makes them predominant candidates for the modification of complex molecules. Without pre-activation, direct

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

• of the alkyl halide and C–H activation can be increased by the presence of active Lewis acid sites on the iron(III) nanoparticles. The scope for this catalytic system can be figured out by the presence of high temperature, high ligand concentration and activated ligands. Chen and co-workers

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• hydride, and C–C bond-forming reductive elimination. Computational results indicate the origin of regioselectivity is involved in the reductive elimination step. Keywords: C–H activation; density functional theory; hydroacylation; iridium catalysis; regioselectivity; Introduction Organic synthesis is

• revolutionized the modern chemist’s synthetic toolbox, prior installation of these functional groups requires a number of steps, leading to undesired side-products and reduced overall yield. An attractive alternative is the catalytic activation and subsequent functionalization of otherwise inert carbon–hydrogen

• /mol less stable while IN2b is 2.0 kcal/mol more stable (Figure 1). As such, it is likely these two intermediates are strongly in equilibrium with no thermodynamic driving force favoring one over the other; moreover, the activation energies of the forward and reverse reactions are proportional. The

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• Radovan Sebesta Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia 10.3762/bjoc.18.28 Keywords: asymmetric organocatalysis; covalent activation; noncovalent activation; Asymmetric catalysis is

• within the area. Organocatalytic reactions are highly suitable components of cascade transformations as exemplified by the seminal work of Enders [13]. Besides traditional enamine and iminium activation of carbonyl compounds other activation modes were uncovered which significantly broadened the

• repertoire of chemical transformations that are amenable to organocatalysis [14]. Within the realm of covalent activation, chiral carbenes and phosphines are diverse and structurally rich groups of catalysts. The synthetic scope was greatly expanded by noncovalent activation via a range of proton-mediated

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• derivative in good yield, albeit with a considerable diminishment in the ee (Scheme 4). Based on the literature reports and the stereochemical outcome, a plausible transition state is proposed, as shown in Figure 2. The activation of nitrosobenzene was achieved by the intramolecular hydrogen-bonding of the

Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• Phil Servatius Uli Kazmaier Organic Chemistry, Saarland University, Campus C4.2, 66123 Saarbrücken, Germany 10.3762/bjoc.18.19 Abstract A peptide Claisen rearrangement is used as key step to generate a tetrapeptide with a C-terminal double unsaturated side chain. Activation and cyclization give

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• -catalyzed norbornene-mediated C–H activation [35] failed and gave 1,4-bis(2-bromophenyl)piperazine-2,5-dione (22, Scheme 5) as the sole product in 61% yield, which to our knowledge is not documented in the literature yet. Synthetic pathway (c) started from methyl 4-(2-nitrophenyl)-3-oxobutanoate prepared in

Mechanistic studies of the solvolysis of alkanesulfonyl and arenesulfonyl halides

• Malcolm J. D’Souza and
• Dennis N. Kevill

Beilstein J. Org. Chem. 2022, 18, 120–132, doi:10.3762/bjoc.18.13

• of 2,4-dimethoxybenzenesulfonyl chloride and of the 2,4,6-trimethylbenzenesulfonyl chloride in 50% TFE/50% water (50% TFE) and in the highly ionizing 97% TFE. They found no evidence for an unusually rapid reaction in these solvents and very negative entropies of activation (consistent with a

• from linearity in Arrhenius plots, which with conventional kinetic studies would be masked by a larger random scatter within the different determinations. A precise detailed treatment allowed the “second-order” heat capacities of activation (∆Cp#) to be determined for, among many other substrates

• acknowledged, in his participation as a co-author of a chapter in “Progress in Physical Organic Chemistry” [31], that this equilibrium needs to be incorporated into treatments based on the magnitudes of the heat capacities of activation (∆Cp#). The need to incorporate the return from an ion pair to a covalent

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

• , Germany 10.3762/bjoc.18.8 Keywords: C–H activation; 3d transition metals; green chemistry; late-stage functionalization; sustainability; Transition metal catalysis has emerged as a transformative platform for the assembly of increasingly complex compounds, with enabling applications to natural product

• witnessed major momentum in metal-catalyzed C–H activation [4][5] as a more resource-economical strategy. This approach involves the efficient and selective cleavage of otherwise inert, yet omnipresent C–H bonds. This strategy avoids a variety of steps and reduces the amount of chemical waste. Very recently

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

• cyclic amines than the aerobic oxidation system. The catalytic cycle for the hydrogen peroxide system involves the formation of the oxoruthenium species (A) and the low-valent ruthenium species (B), whereas the aerobic oxidation system includes C–H activation and a subsequent reaction with molecular

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• 1% in proteins, but is highly conserved in binding sites on protein surfaces mediating PPI [43], it is an attractive target for the development of selective diversifications. C–H activation of the indole C2 position by Pd-catalysis allows both selective arylation [44][45][46][47][48] and formation

• of macrocycles [49]. The macrocyclisation technique by tryptophan C2–H activation has been further improved showing structurally constrained peptides bearing a side chain connection of tryptophan and phenylalanine or tyrosine [50]. Moreover, a similar Pd-mediated approach for C(sp3)–H activation of

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

• strategy for aldehyde C–H activation. The acyl radicals generated in this step were arylated with aryl bromides through a well stablished nickel cross-coupling methodology, leading to a variety of interesting aryl ketones in good yields. We also performed computational calculations to shine light in the

• interchanging steps, often required in traditional synthetic methodologies [1][2]. The development of photocatalysis enabled inexpensive access to C–H activation methodologies under mild conditions, with hydrogen atom transfer (HAT) reactions standing out as a main strategy [1][3][4]. The hydrogen abstractor is

•  2a). Suga and co-workers reported an electrochemical approach for P–H bond activation promoted by this reactive species, leading to the synthesis of several phosphacycles [24] (Figure 2b). Concomitantly with the development of our work, some photocatalytic strategies for DABCO activation emerged. Li

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

• Tanmoy Halder and
• Somnath Yadav

Beilstein J. Org. Chem. 2021, 17, 2915–2921, doi:10.3762/bjoc.17.199

• described in Scheme 2. With the monosaccharide building blocks in hand, the galactosamine donor 6 was coupled with galactose acceptor 7 by activation of the thioglycoside using N-iodosuccinimide (NIS) in the presence of TMSOTf to afford the desired disaccharide β-ᴅ-GalpNHTroc-(1→4)-α-ᴅ-Galp (4) in 85% yield

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

• significant development over the past 10 years. First achieved by Li and co-workers in 2007 [44], cross-dehydrogenative-coupling (CDC) reactions offer a highly atom economic approach to carbon–carbon (C–C) and carbon–heteroatom (C–X) bond formation via C–H activation [45][46]. Generally speaking, C–C bond

• dihydrofurans [102]. In 2019, the Li group studied the selective activation of the α-C(sp3)–H of ketones and esters 103 for the tandem addition/cyclization of o-vinylanilides 102 (Scheme 20) [103]. Through a series of mechanistic experiments, it was noted the cleavage of the C(sp3)–H bond may be involved in the

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• aryl–aryl cross-coupling using various transition-metal catalysts has rarely been successful for the enantioselective construction of hindered biaryls [39] due to the discord between the temperature tolerance of the rotational axis and the high temperature required for C–H activation and suffered from

• be prepared by asymmetric C–H activation. The C–H activation or functionalization can be achieved by a metal-catalyzed chiral phosphoric acid ligand-assisted method, which offers distinct possibilities to provide various chiral biaryl compounds by changing different directing groups (DGs) [46]. Since

• 16 via β-H elimination using (S)-CPA 4 as a ligand (Scheme 7) [51]. The directing group (NH2) facilitated the C–H activation on the other aromatic ring and ensured its coordination with Pd to form palladacycle I-2 to restrict bond rotations and promote exclusive allylic selectivity via β-H1