Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• reaction of aldehydes and ketones with indole [93][94]. Bidentate halogen-bond donors are efficient catalysts, since they can form two halogen bonds with each substrate, instead of just one. Thus, compounds 24, 25 and 26 were screened for their catalytic activity with 26 emerging as the optimum choice

• produce a wide range of bis(indolyl)methanes 28 in good to excellent yields (62–93%) [93][94]. Regarding the mechanism of action of this methodology, two halogen bonds are formed between the bidentate halogen-bond donor 26 and the oxygen of the carbonyl group (Scheme 12). This increases the

• organocatalyst (Scheme 13) [95]. Haloalkynes have the ability to form strong, directional and selective halogen bonds, which makes them a good choice for the synthesis of BIMs [95]. Several substituted carbonyl compounds, as well as indoles, were screened in the optimum reaction conditions as seen in Scheme 13

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

• understood. Intramolecular halogen bonds might be expected to block the proximal (strong) σ-hole and prevent fluoride addition at that site (64a, Figure 14); however, computational results suggested that adduct formation at the strong σ-hole was key to the chemoselective reductive elimination of the

• structures of ylides 76c and 76e confirmed these interactions as intramolecular halogen bonds at lengths of 2.7 Å (Figure 17), and showed intermolecular halogen bonds with iodine’s remaining σ-hole, at bond lengths of 3.3 Å or 3.4 Å. Though the σ-hole syn to the arene was blocked, when these six ylides were

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

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• previous studies, several of these interactions were already applied such as metal–ligand interactions [13][14], hydrogen bonds [15][16] or halogen bonds [17]. Furthermore, π–π interactions also feature a reversible behavior and were therefore utilized for the design of different self-healing polymers [18

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• ‘guests’ within the crystal lattice, through hydrogen-bonding and van der Waals forces. Thereafter, research over the crystal engineering of porphyrins has focused on the noncovalent interactions, such as hydrogen bonds and halogen bonds, or metal coordination interactions [2][3][4][5][6][7][8][9][10][11

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

• solvent (Scheme 57). The complex is bound together by weak halogen bonds, in which phosphorus lone-pair electrons interact with σ* orbitals of C–I bonds. A variety of arylphosphonates can be directly afforded by the simple combination of diaryliodonium salts and phosphite esters. In addition, calculations

Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• liquid crystalline phase was observed for the NO2-C10∙∙∙F2Az and NO2-C10∙∙∙F2’Az assemblies (see Figure 5). In contrast, the highly fluorinated azo compounds F4Az and F3Az with a stronger polarisation on the iodine atom form sufficiently strong halogen bonds with NO2-C10 to extend the mesogenic core and

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• with a quantum yield of ΦP = 2.9% in the crystalline state: this behavior was caused by intermolecular halogen bonds from the carbonyl-oxygen atom to an adjacent bromine atom (Figure 1a). Despite multifarious examples of RTP in the crystalline state, purely organic compounds showing RTP in solution are

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• applicability of the catalysts in two-phase homogeneous catalysis because it allows easy recycling [85] and separation from the reaction mixture [8]. Carbon–halogen bonds are more activated than carbon–hydrogen bonds and hence the halogen is more labile and preferentially displaced. Brill et al. [86] took

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• structural chemistry is governed by halogen bonding, where I− and I3− are considered the nucleophilic (halogen bond acceptor) and I2 the electrophilic (halogen bond donor) subcomponent [3][4][5][6][7]. Neutral halogen bonds on the other hand can be generally described by R–X···Y, where R–X is the halogen

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• inversion, the two conformations show different dimerization modes (Supporting Information File 1, Figure S3). In 1&DIOFB_A, the two hex-NARBrs are linked by two DIOFB molecules via four Br···I halogen bonds with average RXB of 0.86. The two participating bromide anions are on adjacent “arms”; the remaining

• to fill the space. The relatively strong halogen bonds in 1&DIOFB_A partially account for its larger population occupancy than 1&DIOFB_B. In both modes, there is no solvent-accessible space between the dimerized resorcinarene salts. The halogen bond donors connect the two resorcinarene like a solid

• observing halogen bonds in solution. Despite this limitation, NMR spectroscopy is one of the most powerful tools for observing and studying XB systems in solution [37][38][39][40][41]. The bromide anions of the NARBrs are hydrogen-bonded to the hydrogens of the ammonium groups and to the phenolic hydroxy

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• [112]. In this work they have also demonstrated that metallic pnictogens do form sufficiently strong halogen bonds to enable co-crystal formation. Mal and co-workers have shown that a contact explosive, i.e., the mixture of primary amines and phenyliodine diacetate led to a high-yielding reaction at

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• -hydroxyalkanoates from the reaction of α-halocarbonyl compounds with aldehydes or ketones in the presence of zinc [1]. Today, the Reformatsky reactions are more generally defined as metal insertion into carbon–halogen bonds which are activated by carbonyl groups or related functions at vicinal or vinylogous

Stereochemical outcomes of C–F activation reactions of benzyl fluoride

• Neil S. Keddie,
• Pier Alexandre Champagne,
• Justine Desroches,
• Jean-François Paquin and
• David O'Hagan

Beilstein J. Org. Chem. 2018, 14, 106–113, doi:10.3762/bjoc.14.6

• , Université Laval, Québec, QC G1V 0A6, Canada 10.3762/bjoc.14.6 Abstract In recent years, the highly polar C–F bond has been utilised in activation chemistry despite its low reactivity to traditional nucleophiles, when compared to other C–X halogen bonds. Paquin’s group has reported extensive studies on the

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• –nucleobase conjugates A1–A3. ORTEP diagram of 2 at 50% probability level. The hydrogen and halogen bonds are represented by dashed lines. Selected bond lengths (Å) and angles (°): O26–C17, 1.223(2); O27–C21, 1.233(2); O28–C23, 1.225(2); N20–C25, 1.380(2); N22–C21, 1.372(2); N22–C23, 1.389(2); C1–C17, 1.501(2

Mechanochemical Knoevenagel condensation investigated in situ

• Sebastian Haferkamp,
• Franziska Fischer,
• Werner Kraus and
• Franziska Emmerling

Beilstein J. Org. Chem. 2017, 13, 2010–2014, doi:10.3762/bjoc.13.197

• interactions such as hydrogen bonds, halogen bonds, and π∙∙∙π interactions [16][17][18][19]. For example, Toda et al. reported yields of 97% for Aldol condensations in the absence of any solvents [20]. Kaupp et al. described the first Knoevenagel condensation in a ball mill [21]. Compared to conventional

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• organic catalysts for electrophile activation through the formation of C–H hydrogen bonds and C–X halogen bonds. Keywords: C–H hydrogen bond; counteranion activation; electrophile activation; halogen bond donor; hydrogen bond donor; organocatalysis; Review Introduction Over the past century chemists

• –4 M−1) between L14 or L15 and lactide in solution. The α-dichloro and α-dibromoacetanilides L14 containing electron-deficient aromatic groups (i.e., m,m’-NO2 substitution on phenyl ring) afforded the most active catalysts with the strongest N–H···O···H–CX2 interactions. Halogen bonds as alternatives

• containing a halogen (I···N) bond [70]. When chiral organohalides form halogen bonds with chiral acceptors, diastereomeric complexes may be formed. Thus, in 1999, Resnati reported the resolution of racemic 1,2-dibromohexafluoropropane through halogen-bonded supramolecular helices (Scheme 13) [69]. When

Efficient synthesis of π-conjugated molecules incorporating fluorinated phenylene units through palladium-catalyzed iterative C(sp²)–H bond arylations

• Fatiha Abdelmalek,
• Fazia Derridj,
• Safia Djebbar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2015, 11, 2012–2020, doi:10.3762/bjoc.11.218

• very chemoselective, as the reactions only involve desulfitative coupling even in the presence of C–halogen bonds [57], which allow further orthogonal transformations. Moreover, a wide scope of benzenesulfonyl chlorides is commercially available at an affordable cost. We report herein, a new synthetic

The crystal structure of the Dess–Martin periodinane

• Albert Schröckeneder,
• Desiree Stichnoth,
• Peter Mayer and
• Dirk Trauner

Beilstein J. Org. Chem. 2012, 8, 1523–1527, doi:10.3762/bjoc.8.172

• periodinane; halogen bonds; hypervalent iodine; oxidant; Introduction The so-called Dess–Martin periodinane (DMP, 1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one, 1) has emerged as one of the most useful reagents for the oxidation of primary and secondary alcohols to the corresponding aldehydes and

• . The intermolecular iodine–oxygen distance of 3.3 Å lies well below the sum of the van der Waals radii (3.46 Å) [11]. Angles of 159.1° (C3a–I1a–O8b) and 120.2° (I1a-O8b-C12b) are also in accordance with the presence of halogen bonds [12]. Similar bonds between iodine atoms and sp2-hybridized oxygen

• atoms have been observed in a range of other hypervalent iodine species [7][8][13][14][15][16][17], as well as iodine(I) compounds [18][19]. The ability to form halogen bonds may also account for the high solubility of DMP (1) in organic solvents. In addition to halogen bonds, the dimer is stabilized by

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• insertion of Mg in the presence of LiCl The presence of LiCl facilitates greatly the insertion of many metals into carbon-halogen bonds and avoids the use of expensive activated forms of Mg, such as “Rieke-magnesium”. This property of LiCl for accelerating the insertion of Mg to organic halides has found

The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts

• Kari Raatikainen,
• Massimo Cametti and
• Kari Rissanen

Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4

• chemistry [2]. Halogen bonding (XB) is the non-covalent interaction involving halogen atoms as electrophilic species [3]. The first reports of these interactions, only later classified as halogen bonds, date back to the late 1960’s [4]. In the following years, several X-ray studies demonstrated the

• halogen bond donors. Iodonitrobenzene derivatives represent a less explored type of haloarenes [29][30]. In these XB systems, secondary C–I···O2NAr halogen bonds (distances 13% shorter than the sum of standard VDW radii [17]) have been observed for iodonitrobenzenes themselves [31][32] or in co-crystals

• of iodo- and nitrobenzenes [29][30]. In our recent studies [33], we have shown that 1-iodo-3,5-dinitrobenzene forms surprisingly strong C–I···N halogen bonds (23% shorter than the sum of standard VDW radii [17]) with 1,4-diazabicyclo[2.2.2]octane (DABCO). One of the main challenges in supramolecular