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

• general strategy, in 2014, Rueping and co-workers reported the pioneering contribution concerning the synthesis of indoles via an intramolecular C–H/C–H oxidative coupling of N-arylenamines under air atmosphere. This procedure was based on dual catalysis involving a double C–H activation system 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

• bipyridyl units have been designed to immobilise transition metal complexes through coordinate bonding for the oxidative coupling of amines [138]. [Ru(bpy)3]2+ units were synthesised with ethynyl groups para-substituted to the nitrogen heteroatom on four of the six pyridine rings. The ethynyl groups were

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• oximes reacted with esters and ketones to give oxidative coupling products in moderate to good yields (products 55a–e and 56a–e, respectively). In the case of asymmetric ketones, the C–H bond at the more substituted carbon was cleaved (products 56d,e). Recently, the copper-catalyzed addition of oximes to

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• phenol by oxidative coupling reactions and acidic functional groups decrease the amount of adsorbed phenol [51][127][128]. Duman and co-workers studied different pyrolysis temperatures and activation times with ZnCl2 for the preparation of highly porous activated carbon from fruit stones and nutshells

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• this case, the authors observed the oxidative coupling between the primary amines and their respective imines to produce the secondary imines. Wang and co-workers reported the synthesis, characterization, and application of interesting metal-free heterogeneous photocatalysts, 2D porphyrin-COFs (Por-COF

• methodology (conditions A). However, when primary amines were used, the authors observed an oxidative coupling between the amines and their respective N-substituted imines, which were trapped with TMSCN to afford the corresponding nitriles. The authors solved this problem by cooling the reaction to −50 °C and

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• disadvantage may be obviated by transition-metal-mediated double C–H bond activation [22][23], which is functionally equivalent to conventional oxidative coupling reactions, and has become a powerful synthetic tool with a rapidly growing scope of use [24][25][26]. However, in the field of π-conjugated

• into boomerang-shaped N,N'-bridged α,α'-bipyrroles that are not accessible by means of conventional oxidative coupling methods (Scheme 1) [32]. Our approach is applicable to electron-deficient and sterically encumbered systems, notably those based on pyrrole derivatives fused with naphthalenediamide

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• for the construction of such polycyclic scaffolds, and the last decade has witnessed a remarkable improvement in the palladium-catalyzed C–H/C–H oxidative coupling as one of the potential synthetic strategies [1]. This method is straightforward and highly step-economical, enabling us to produce

• BINOL derivatives [37][38][39]. In this context, we herein describe the synthesis of axially chiral BINOL-derived BBZFPys through the palladium-catalyzed oxidative coupling reaction. The optical properties of the synthesized polyaromatic compounds were systematically studied, and some of them displayed

• . Intramolecular stacking structures of 4b and 4c. Synthesis of BBFZPys through the Pd-catalyzed C–H/C–H coupling. Synthesis of 3a–c. Synthesis of 4a–c through oxidative coupling reaction. Synthesis of 6. Florescence properties.a Calculated dimensionless dissymmetry factors.a Supporting Information Supporting

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• following three categories: (i) by Wittig or Doebner reaction of indoles bearing a 3-aldehyde group; (ii) by 1,4- or 1,2-addition of α,β-enones or carbonyl compounds, followed by oxidation or elimination, respectively; (iii) by Pd-catalysed oxidative coupling of indoles with activated alkenes. Several

Synthesis and characterization of bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives

• David Martínez-López,
• Amirhossein Babalhavaeji,
• Diego Sampedro and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2019, 15, 3000–3008, doi:10.3762/bjoc.15.296

• than 1 [10]. Figure 2 also shows experimental spectra, which are discussed below. Synthesis The overall synthetic route that was taken is shown in Scheme 1. The azo compound 8, carrying two ortho-methoxy groups, was prepared from 7 using an oxidative coupling approach [19]. The para-chloro substituents

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• for the electrocatalytic oxidative coupling of 42 using constant potential electrolysis of the substrates on a graphite felt electrode modified with TEMPO in the presence of (−)-sparteine 43. The electrolysis resulted in (S)-binaphthyl type dimers 44 with excellent yield and enantiomeric excess

• methyl sulfide using chemically modified graphite anode. Asymmetric oxidation of unsymmetric sulfides using poly(amino acid)-coated electrodes. Enantioselective, electocatalytic oxidative coupling on TEMPO-modified graphite felt electrode in the presence of (−)-sparteine. Asymmetric electrocatalytic

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• widely described in the literature encompassing a number of reactions like oxidative cyclizations [11], oxidative coupling reactions [12], Vilsmeier type cyclizations [13], intramolecular aminooxygenation/C–H amination reactions [14][15], Groebke–Blackburn–Bienayme (GBB) reactions [16][17][18] and many

• and EDGs were also well tolerated by pyridinium ylides. The group of Bharate and Abbat have successfully reported a simple, efficient and excellent C–N bond formation catalyzed by CuBr [124]. The protocol involved the aerobic oxidative coupling of 2-APs with cinnamaldehyde to form 3-formyl-2

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• highly oxygenated aryl rings. Scorzodihydrostilbene E (5) features a dimeric skeleton that originates from an oxidative coupling of compound 1. The natural products exhibited antioxidative activity that was partly stronger than that of the well-known naturally occurring antioxidant resveratrol [5]. In

Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

• Miriam Schehr,
• Daniel Hugenbusch,
• Tobias Moje,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2018, 14, 2799–2804, doi:10.3762/bjoc.14.257

• derivatives [18][19]. Towards the synthesis of S-diazocines (Figure 1), two general approaches could be derived from the well investigated azobenzene preparation methods: a) Reductive coupling of two nitro groups or b) oxidative coupling of two amino groups [20]. To cleanly form N=N bonds by reduction of

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• medicinal chemistry. This is a reflection of the tendency of synthetic bioactive molecules to exhibit peptidomimetic properties. Though there is a vast number of procedures that generate amide bonds, an interesting approach is taken by Leow, who has demonstrated the synthesis of amides through the oxidative

• coupling of aromatic aldehydes and a wide range of secondary amines, using mesitylacridinium salts as the photocatalysts (Scheme 1) [38]. The main advantage is the use of air as the oxidant, which converts the formed α-hydroxy amine into the desired amide. This makes for a much more atom economical and

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• (15). Iodine(III)-mediated spirocyclization of alkyl hydroxamates 50 to spirolactams 51 using stoichiometric amount of PIFA (31). PIFA-mediated cyclization of substrate 52 to spirocyclic product 54. Synthesis of spiro β-lactams 56 by oxidative coupling reaction of p-substituted phenols 55 using PIDA

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• %) along with the N7 stereoisomer (10%). These results support the above-mentioned hypothesis. Finally, 4'-thioadenosine (49) was synthesized by treating 45 with TFA followed by methanolic ammonia [46] (Scheme 5). The same group attempted to apply the oxidative coupling reaction to the synthesis of

• nucleobase by using a combination of hypervalent iodine and an appropriate Lewis acid (Figure 4). As shown in Scheme 12, an oxidative coupling reaction was examined using a model reaction [63]. Cycloalkenylsilanes 89a,b and 90a,b were prepared by hydrosilylation of cyclopentadiene and cyclohexadiene. Using

• (PhI(OH)OTs) resulted in a decrease of the reaction yield (Table 2, entries 5–7). To prove the usefulness of the oxidative coupling reaction mediated by hypervalent iodine, the reaction was applied to the synthesis of a carbocyclic nucleoside derivative designed as a potential anti-HIV agent. As a

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• results of our extensive study and optimization of our radical C–H activation strategy for the intermolecular oxidative coupling between the benzylic secondary C–H bond and the O–H group of carboxylic acids (Scheme 1). Results and Discussion Benzylic C–H carboxylation can provide a convenient route to

• ) acetate [74] for substrates 1b–d and benzyl acetates 2b–d were obtained in moderate to excellent yields after prolonged reaction times (Table 2, entries 1–4). Furthermore, iterative oxidative coupling at the aromatic and benzylic C–H position using hypervalent iodine chemistry is possible, and 1-ethyl-4

• oxidative coupling with carboxylic acids. Radical reactivities of the I(III)–Br bond generated from PIDA. Benzylic C–H carboxylations by the iodosobenzene/NaBr system. Outline of the proposed reaction mechanism for the PIDA/NaBr system. Reaction of benzyl bromide 2h’ under radical C–H acetoxylation

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• transition metal catalyst Cu(OTf)2, Wu and co-workers achieved aerobic oxidative coupling of secondary amines with β-keto esters to form C(sp3)–C(sp3) bonds (Scheme 1) [18]. Although much advance has been made for the functionalization of glycine derivatives, most of these strategies mentioned above require

• catalyst, the yield of 3aa increased to 81% (Table 1, entries 16–19). On the basis of the screening of reaction conditions, we could conclude that the electrocatalytic oxidative coupling should be performed in a mixed solution of CH3CN and CH2Cl2 (v/v = 1:2), in the presence of n-Bu4NI (30 mol %) as the

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• , Lebanon Université de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226, Avenue du Général Leclerc, 35042 Rennes Cedex, France 10.3762/bjoc.13.208 Abstract Using an aerobic oxidative coupling, different new imidazo[1,2-a]-N-heterocycles with gem-difluroroalkyl side chains have been

• coupling reactions as well as nucleophilic substitutions have been performed successfully in order to increase the molecular diversity. Keywords: aerobic oxidative coupling; imidazo[1,2-a]-N-heterocycles; gem-difluoroalkyl derivatives; propargylic fluorides; Introduction Nitrogen-containing heterocyclic

• (II) acetate-catalyzed aerobic oxidative amination and it proceeds through a tandem Michael addition followed by an intramolecular oxidative amination. Therefore, our target molecules A could be synthesized by the oxidative coupling of 2-aminopyridines with α,β-unsaturated ketones B, themselves easily

Transition-metal-free synthesis of 3-sulfenylated chromones via KIO₃-catalyzed radical C(sp²)–H sulfenylation

• Yanhui Guo,
• Shanshan Zhong,
• Li Wei and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2017, 13, 2017–2022, doi:10.3762/bjoc.13.199

• transition-metal-free oxidative coupling has emerged as a powerful complementary tactic in C(sp2)–S bond forming reactions [16][17][18][19][20][21][22][23][24][25][26][27]. As a beneficial and sustainable approach, such transition-metal-free cross coupling transformations have been successfully employed in

Synthesis of oligonucleotides on a soluble support

• Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

• oligonucleotides and most of these attempts have concerned the preparation of phosphorothioate ODNs, as discussed below. The only successful synthesis of unmodified ODNs was based on oxidative coupling of alkyl H-phosphonates on a PEG support [65]. The 3´-terminal nucleoside was immobilized to a PEG support via a

α-Acetoxyarone synthesis via iodine-catalyzed and tert-butyl hydroperoxide-mediateded self-intermolecular oxidative coupling of aryl ketones

• Liquan Tan,
• Cui Chen and
• Weibing Liu

Beilstein J. Org. Chem. 2017, 13, 1079–1084, doi:10.3762/bjoc.13.107

• self-intermolecular oxidative coupling of aryl ketones using I2−tert-butyl hydroperoxide (TBHP). Under the optimum conditions, various aryl ketones gave the corresponding products in moderate to excellent yields. A series of control experiments were performed; the results suggest the involvement of

• H2O in the TBHP solvent. Keywords: aryl ketones; iodine; self-intermolecular oxidative coupling; self-sequential assembly; TBHP; Introduction In recent years, α-acetoxyaryl ketones have attracted considerable interest because this structural motif is found in a variety of biologically active natural

• transition-metal-catalyzed direct oxidative coupling reactions of carbonyl compounds with carboxylic acids (or their surrogates) [8][9]. Recently, robust approaches using organohypervalent iodine reagents and peroxide-mediated oxidative coupling have been developed [10][11]. Although impressive progress has

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• reported a metal-free photocatalytic aerobic oxidation of thiols to disulfides under continuous-flow conditions [64]. Disulfides are useful molecules employed as drugs, anti-oxidants or pesticides as well as rubber vulcanizating agents [65]. Symmetric disulfides are generally obtained by oxidative coupling

A versatile route to polythiophenes with functional pendant groups using alkyne chemistry

• Xiao Huang,
• Li Yang,
• Rikard Emanuelsson,
• Jonas Bergquist,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 2682–2688, doi:10.3762/bjoc.12.265

• quinone moieties are vulnerable in nucleophilic and acidic environments. Furthermore, the viologen moiety, available from 4,4’-bipyridine (BP) has potential for energy storage and electrochromic applications [35][36], but it has previously been anchored to a polymer backbone only by oxidative coupling via