Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• paradigm with photocatalytic ATRA to enable the modular difunctionalization of alkenes under reagent control (Scheme 3). In Stephenson’s photocatalytic ATRA reports, the C–X bond in the product was proposed to be formed through both direct quenching of a transient alkyl radical by halogen atom transfer

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• Carlee A. Montgomery Graham K. Murphy Department of Chemistry, University of Waterloo, 200 University Ave W., Waterloo, Ontario, N2L3G1, Canada 10.3762/bjoc.19.86 Abstract Halogen bonding is commonly found with iodine-containing molecules, and it arises when Lewis bases interact with iodine’s σ

• -holes. Halogen bonding and σ-holes have been encountered in numerous monovalent and hypervalent iodine-containing compounds, and in 2022 σ-holes were computationally confirmed and quantified in the iodonium ylide subset of hypervalent iodine compounds. In light of this new discovery, this article

• provides an overview of the reactions of iodonium ylides in which halogen bonding has been invoked. Herein, we summarize key discoveries and mechanistic proposals from the early iodonium ylide literature that invoked halogen bonding-type mechanisms, as well as recent reports of reactions between iodonium

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• a halogen atom transfer (XAT) agent [101]. While yields of the monophotonic oxidative quenching route and the (biphotonic) conPET reductive quenching route were generally well comparable, the RQ route clearly benefits from a longer lifetime of the key catalytic species, shorter reaction times and

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• –h in 57–65% yields. Also, the halogen-substituted arylamines such as p-bromo, o-bromo, p-chloro, and p-fluoroanilines reacted smoothly to produce the corresponding diarylamine products 3i–l with 65–73% yields. To identify the effect of steric hindrance we treated 2,6-dimethylaniline under optimal

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

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

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• reaction pathway opens that involves either the E2 or E1cB-like mechanism to give the corresponding nitrile X and thiolate IX, which can be further alkylated with an excess of α-halogen component to give a symmetrical sulfide. Only in very few cases when the starting α-thioiminium salt III contains an

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• ). In contrast to the effect reported for NO2 and CF3 substituents by Tokmakov and Grandberg [48], electron-withdrawing halogen substituents on the aryl ring did not prevent rearrangement to dibenzo[b,f]azepine 43 [49]. The isolated yield of unsubstituted 43 was good (67%), however, substitution

• bromides and electron-withdrawing groups. The authors found that the addition of potassium iodide, and thus in situ palladium-catalysed halogen exchange, improved the yield of dibenzo[b,f]azepine 110. Unsymmetrical derivatives of 110 containing -CO2Me, -CF3, -NO2 and -CN substituents were synthesised in

• from 2-bromostyrene (116) via halogen–lithium exchange and quenching with the appropriate heteroatom source (SiR2Cl2, SnMe2Cl2, GeR2Cl2, BBr3). P-Tethered dienes were synthesised via quenching of a 2-vinylphenyl Grignard reagent with phenylphosphonic dichloride (PhPOCl2). O-Tethered dienes were

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• the aryl ring – as electron-releasing groups (Me, OMe) showed little more reactivity than electron-withdrawing groups (CN) at the same position (4b, 4f, and 4g). Halogen-substituted IPs also followed the general reactivity trend of the respective halogens (4c–e). Excellent reactivity was found for o-F

• diverse electronic properties were present in the pyridine ring of the IP moieties (4l–q). With substrates having a methyl substitution at C-7 and C-8 of the pyridine ring, the yields and regioselectivity were still excellent (4l and 4m), but reduced significantly upon introducing a halogen group onto the

• pyridine ring. Except for the 6-bromo-substituted compound (4o), all other substrates having a halogen substituent in the pyridine ring showed reduced yields (4n, and 4p,q). The number of substituents also seemed to negatively affect the yield, as observed for products 4p and 4q, featuring two substituents

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• array of organic synthetic transformations. Enolates are usually formed by deprotonation of the corresponding organic compound. However, other synthetic approaches for their generation exist, such as cleavage of enol ethers and esters, halogen–metal exchange, transmetalations, and conjugate additions to

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• , the process is driven by the photochemical activity of halogen-bonded complexes formed upon complexation of a sacrificial donor, namely 1,4-diazabicyclo[2.2.2]octane (DABCO), with α-iodosulfones. The reaction provides a variety of densely functionalized products in good yields (up to 96% yield

• deuterated acetonitrile (Figure 3). Interestingly, a change in chemical shift of the diagnostic α-protons of 2a was displayed upon addition of increasing amounts of DABCO, suggesting the presence of the halogen-bonding interaction [30]. More precisely, the 1H NMR signal of the α-hydrogens (Hα) within 2a was

• found to shift to lower ppm values because the Hα nuclei have been affected by higher electron density caused by the formation of the halogen-bonded complex between 2a and DABCO. To confirm that the shift of Hα was indeed produced by a halogen-bonding interaction, 19F NMR analysis of compound 2d, which

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• -Cl [21], 3,4-di-Cl [21][22], 2/3/4-F [23]) were inserted in the N-benzyl moiety as well as in the aromatic rings of the benzophenone fragment [24][25][26] (selected examples are given in Scheme 1). Insertion of halogen atoms increased enantioselectivity, e.g., in alkylation reactions [27][28

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• % yields, respectively. This reaction proved to be compatible with the presence of an ester (8c) or a halogen (8e). Other directing groups, such as substituted pyridines (9a and 9b) and pyrimidine (9c) turned out to be also efficient in this transformation (Scheme 5, 4 examples, up to 84% yield). The same

• , up to 91% yield) [119]. 2-Arylpyridine derivatives bearing electron-donating groups, electron-withdrawing groups or halogen at the para- and meta-positions of the aromatic ring were readily functionalized (11a–g, 58–85% yields). Also 2-(2-methoxyphenyl)pyridine (11h) and 2-(2-naphthyl)pyridine (11i

• methyl, methoxy or methylthio groups (17b–d) or by halogen (17e) was achieved (Scheme 8, up to 77% yield). Note that in case of disubstituted 2-(4-ethoxy-3-fluorophenyl)pyridine (17h), the expected product 18h was isolated in 31% yield. Moreover, selective oxidation of the SCF3 residue into the

Synthesis and reactivity of azole-based iodazinium salts

• Thomas J. Kuczmera,
• Annalena Dietz,
• Andreas Boelke and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 317–324, doi:10.3762/bjoc.19.27

• aryl donors [11][12][13][14][15][16]. Their cyclic derivatives have a proven utility as precursors for the synthesis of hetero- and carbocycles [17][18][19][20][21], and their pronounced σ-holes [22] render them efficient halogen-bond donors (XB donors in XB catalysis) [23]. Despite their great

• observed a coordination of the triflates along the C–I axis with distances of 2.705 Å (I1–O1) and 2.898 Å (I1–O5). For the ortho-methyl-substituted analogue 5ax, no halogen bonding to the triflates was observed, indicating an effective steric protection of the σ-holes [36]. Instead, there were only two

• result obtained when using the stabilized salt 12 (Scheme 2b) [44]. Here, no counter-ion exchange to chloride was observed. The favored counter ion is determined by the pKa value of the corresponding acids but not by halogen bonding due to the steric hindrance at the iodines’ σ-holes. The reaction of

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• , delivering a variety of structurally diverse isocoumarins in an efficient manner (3aa–qa, 43–82%). It is worth mentioning that the tolerance of halogen substituents (Cl, Br and I) may open up a new opportunity for further transition-metal-catalyzed cross-coupling reactions. Sensitive groups, such as ester

Synthetic study toward the diterpenoid aberrarone

• Liang Shi,
• Zhiyu Gao,
• Yiqing Li,
• Yuanhao Dai,
• Yu Liu,
• Lili Shi and
• Hong-Dong Hao

Beilstein J. Org. Chem. 2022, 18, 1625–1628, doi:10.3762/bjoc.18.173

• –Martin oxidation. At this stage, the pivotal C–H insertion step was tried under the reported conditions [34], and cyclopentenone 8 was successfully obtained. Further study with cross coupling or halogen–magnesium exchange shows this moiety is inert for functional group transformation. The attempt for

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• %). Nucleophilic halogenation reactions In 2015, Evgeny I. Adiulin and co-workers reported a methodology for the deoxygenative nucleophilic halogenation of 2-unsubstituted imidazole N-oxides at the C-2 position using tosyl halogenides (TsHal) as halogen donor in THF as the solvent [18]. In this procedure, the

• fluoroborate complexes of the N-oxides O-acylated by TsHal and the cine-substitution occurs with the help of a halogen group releasing the tosyl group. Here, 1.0 equiv 2-unsubstituted imidazole N-oxides were refluxed with 1.0 equiv TsHal in 1.0 equiv pyridine that played the role as both the base and the

Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)

• Yukiko Karuo,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167

• highly halogenated carbon centers, which enable halothane to participate in various reactions such as homolysis of carbon–halogen bonds and deprotonation. Multi-fluorinated compounds such as HCFC-133a (CF3CH2Cl) and HFC-134a (CF3CH2F) have been widely used in reactions with a variety of nucleophiles to

• halothane as a halogen and carbon source. Results and Discussion First, we optimized the reaction conditions for the formation of aryl fluoroalkenyl ethers with phenol (3a) as a model substrate. On the basis of our previous work, we performed the reaction of halothane with 3a under the standard conditions

• react with 4 because the carbanion 6, which is generated from 4 and 5, is less basic because of the double induction effect of the two halogen atoms. In this cycle, 1 can be neutralized in the reaction medium by proton sources such as 3, halothane, and H2O. Dehalogenation of intermediate 6 or removal of

Supramolecular approaches to mediate chemical reactivity

• Pablo Ballester,
• Qi-Qiang Wang and
• Carmine Gaeta

Beilstein J. Org. Chem. 2022, 18, 1463–1465, doi:10.3762/bjoc.18.152

• hydrogen bonding interactions play a pivotal role in catalysis. More recently, halogen bonding interactions have been used as a novel tool to catalyze a wide variety of processes. Other nonclassical interactions, including anion-, chalcogen-, and pnictogen bonding, have also been exploited for the design

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• with Davis’ oxaziridine and subsequent oxidation using Dess–Martin periodinane. Initial attempts for the key step (15 → 16) like a Nozaki–Hiyama–Kishi reaction failed, but lithium–halogen exchange using t-BuLi at low temperatures gave the desired vinyllithium intermediate I which successfully added to

From amines to (form)amides: a simple and successful mechanochemical approach

• Federico Casti,
• Rita Mocci and
• Andrea Porcheddu

Beilstein J. Org. Chem. 2022, 18, 1210–1216, doi:10.3762/bjoc.18.126

• hand, the methodology was successfully applied to the synthesis of several formamides starting from a series of aromatic amines (Scheme 1). The N-formyl derivative 3 was prepared in good yields as well as formanilides bearing halogen substituents, which were well tolerated (Scheme 1, products 4 and 5

Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

• Yara Cristina Marchioro Barbosa,
• Guilherme Caneppele Paveglio,
• Claudio Martin Pereira de Pereira,
• Sidnei Moura,
• Cristiane Storck Schwalm,
• Gleison Antonio Casagrande and
• Lucas Pizzuti

Beilstein J. Org. Chem. 2022, 18, 1079–1087, doi:10.3762/bjoc.18.110

• -substituted arylhydrazone 1b led to 2b in only 10% yield and 4-methoxy-substituted arylhydrazone 1c was not converted to the desired 1H-indazole 2c. Arylhydrazones 1d–f substituted with halogen atoms were converted in 23–53% yield, but for the 4-fluoro- and 5-fluoro-substituted substrates 1d and 1f, a longer

Electrochemical formal homocoupling of sec-alcohols

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masashi Shiota,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• transformation was investigated as shown in Scheme 2. Various 1-arylethanol derivatives were firstly examined. Substrates bearing p-methyl (1b) or p-tert-butyl (1c) groups afforded the desired products 2b and 2c in moderate yields. Halogen substituents such as fluorine (1d) and chlorine (1e) atoms were tolerated

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

• Dharmendra Das,
• Akhil A. Bhosle,
• Amrita Chatterjee and
• Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

• , pharmaceuticals, agrochemicals, and advanced materials [10][11][12][13][14]. The ubiquity of halogen atoms in these synthetic building blocks urges the development of efficient, sustainable, and mild methods for aromatic halogenation. The century-old classical method of using hazardous and corrosive reagents X2

• ) affording high yields of the corresponding monobrominated products. The reaction of halogen-substituted phenols also showed higher yields with no exchange of halogen atoms during the course of the reaction (products 2g–j, Scheme 3). As expected, exclusive ortho-bromination to the phenolic hydroxy group was

• Representative examples of important halogen-containing aryl derivatives. Strategies for halogenation of aromatic compounds using NXS. General scheme of PEG-400-assisted halogenation of phenols and anilines in an automated grinder using NXS. Monohalogenation of phenols and anilines by automated grinding with NXS

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

• Mio Matsumura,
• Kaho Tsukada,
• Kiwa Sugimoto,
• Yuki Murata and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 863–871, doi:10.3762/bjoc.18.87

• halogen groups at the 6-position of the imidazopyridine ring were tested and gave the desired products 4ba–ea in fair to good yields (Table 2, entries 8–11). Conversely, imidazopyridine 1f with an electron-withdrawing trifluoromethyl group did not yield the corresponding product 4fa, because the

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

• using N-halosuccinimides as the halogen source under neat grinding or liquid-assisted grinding conditions in a ball mill has been described. Depending on the azobenzene substrate used, halogenation of the C–H bonds occurs in the absence or only in the presence of PdII catalysts. Insight into the

• -halosuccinimide (NXS, X = Br, I) as halogen source [47]. Two years later in 2017, Eslami's group applied a ball-milling method to synthesize aryl bromides and α-bromoketones with N-bromosuccinimide (NBS) and MCM-41-SO3H catalyst and no liquid additives [48]. In 2018, Wang and co-workers developed the ball-milling

• azobenzenes is strongly influenced by the nature of the azobenzene substituents. Conclusion We have applied a mechanochemical protocol for the halogenation of 4,4’-functionalized azobenzenes in a ball mill under NG or LAG conditions, using NXS (X = Cl, Br, and I) as the halogen source. Halogenation of

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

• % yield. At the same time, arenes containing electron-withdrawing groups (such as halogen and trifluoromethyl) also give the corresponding products 3e–h in moderate yields with the meta substituted isomers as the major products. Interestingly, only the meta product was detected when (trifluoromethyl