Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• used three different types of macrocycles: calix[4]pyrroles 11, 17a–c, porphyrin 18, and calix[4]arene 19 (Figure 4a). Despite the presence of –OH and –NH binding sites, both calix[4]arene 19 and porphyrin 18 showed only a negligible activity compared to calix[4]pyrroles (11, 17a–c), which provided

Extension of the π-system of monoaryl-substituted norbornadienes with acetylene bridges: influence on the photochemical conversion and storage of light energy

• Robin Schulte,
• Dustin Schade,
• Thomas Paululat,
• Till J. B. Zähringer,
• Christoph Kerzig and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 3061–3068, doi:10.3762/bjoc.20.254

• is necessary to accomplish a reasonable balance between the MOST parameters. Hence, to increase the energy density and to induce a decent red shift of the absorption, two, three or even more norbornadiene units may be combined in one integral molecule by attachment to a shared, linking arene unit

• integration of an acetylene bridge between the arene core and the norbornadiene units in compounds 1h–n may induce these effects. Herein, we present the synthesis of these target molecules and our studies of their photochemical and physicochemical properties with a focus on energy conversion and storage

• ones. This lack of correlation may indicate that several different factors and processes contribute to different extent to the course of the photoreaction, for example, steric hindrance and resulting torsion angles between the arene unit and norbornadiene, deactivation of the excited state by

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

Structure and thermal stability of phosphorus-iodonium ylids

• Andrew Greener,
• Stephen P. Argent,
• Coby J. Clarke and
• Miriam L. O’Duill

Beilstein J. Org. Chem. 2024, 20, 2931–2939, doi:10.3762/bjoc.20.245

• the acyclic tetrafluoroborate (1a), triflate (1b), chloride (1c) and nitrate (1d), the anion X– occupies the position trans to the arene substituent, with the ylid in the equatorial position. In tosylates 1e and 1f, as well as the cyclic and pseudocyclic structures 2 and 3, the anion or coordinating

• , with the tosylate trans to the arene in one (θ2 = 177.8) and trans to the ylid in the other (θ1 = 169.5), which suggests that this isomerisation is fast at room temperature and the position of the anion has no significant effect on the stability of these compounds. This hypothesis is further supported

• by the absence of a trans effect. While studies by Ochiai and Suresh found that strong sigma donors X cause a lengthening and weakening of the trans I–R bond in R–I(Ar)–X iodanes [32][33], little variation is observed in the I–C(ylid) (b) and I–C(arene) (c) bonds across the range of compounds

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• method for the regioselective thiolation of aromatic C–H bonds by activating the thiol rather than the arene [19]. For their developed reaction, Pt electrodes were used in an undivided cell with a mixture of HFIP/DCE 3:1 at room temperature under argon. Late-stage functionalization was demonstrated for

• protocol for the installation of sulfonamide groups using commercially available SO2 and amines (Scheme 12) [20]. This method is highly appealing for industrial applications and LSF. The proposed mechanism begins with the anodic oxidation of the arene substrate. The resulting radical cation intermediate is

• leelamine, racemorphan, and analogs of sertraline and celecoxib was achieved with yields ranging from 40% to 92%. The reaction mechanism begins with the photoexcitation of the intermediate [TAC2+•]*, which oxidizes the arene substrate to form a cation radical. This radical is deprotonated and then further

HFIP as a versatile solvent in resorcin[n]arene synthesis

• Hormoz Khosravi,
• Valeria Stevens and
• Raúl Hernández Sánchez

Beilstein J. Org. Chem. 2024, 20, 2469–2475, doi:10.3762/bjoc.20.211

• from intermolecular dehydration, nowadays known as alkyl resorcin[4]arene. Forty years later in 1980, Höegberg noticed that short alkyl chain resorcin[n]arenes develop stereoisomers in the reaction mixture; however, since the condensation reaction is reversible, once the macrocycle adopts the bowl

• -shaped conformation it precipitates out of solution acting as a thermodynamic sink [5][6]. Shortly after, Cram et al. recognized the potential of resorcin[n]arenes as compounds large enough to encapsulate other simple molecules or ions and group them with other known macrocyclic arene compounds, e.g

• molecular recognition [12][46]. Despite extensive research, challenges remain in the acid-catalyzed resorcin[n]arene synthesis, for example: 1) reaction times for simple resorcin[n]arenes starting from aliphatic aldehydes and resorcinol generally require multiple days and up to a week (Scheme 1a) [9][26]; 2

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• of 87% and 64%, respectively. Unfortunately, the synthesis of vanillin (4q) was unsuccessful due to undesirable oxidation reactions of the electron-rich arene. The cyclopropane derivative 4r was generated from the cyclopropylmethanol in 53% yield. The acetylene derivative 4s could not be isolated due

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• on the arene were unsuccessful. Without substituents on the ring, aryl C–H activation and subsequent C–O bond formation occurred along with benzylic fluorination (7) (low efficiency). The presence of a p-methoxy group resulted in a switch in selectivity to acyloxylation 8’ as the major product. The

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• proposed strategy where the metal ion acts as the binding cation template for the intramolecular desymmetrization (Scheme 15) [82]. A similar highly efficient intramolecular Cannizzaro reaction of calix[4]arene dialdehydes was observed by Galli et al. where the 1,3-distal cone 35 significantly responded to

• [4]arene dialdehydes. Desymmetrization of dialdehydes of symmetrical crown ethers using Ba(OH)2. Synthesis of ottelione A (proposed) via intramolecular Cannizzaro reaction. Intramolecular Cannizzaro reaction for the synthesis of pestalalactone. Synthetic strategy towards nigricanin involving an

Auxiliary strategy for the general and practical synthesis of diaryliodonium(III) salts with diverse organocarboxylate counterions

• Naoki Miyamoto,
• Daichi Koseki,
• Kohei Sumida,
• Elghareeb E. Elboray,
• Naoko Takenaga,
• Ravi Kumar and
• Toshifumi Dohi

Beilstein J. Org. Chem. 2024, 20, 1020–1028, doi:10.3762/bjoc.20.90

• a cartridge filled with powdered oxone® for in situ generation of bis(trifluoroacetoxyiodo)arenes and their reaction with electron-rich arene or arylboronic acid [19] (Scheme 1B). Carboxylic acids, such as acetic acid and benzoic acid, characterized by substantial difference in pKa values when

• % yield. Notably, this strategy allowed the synthesis of (diacetoxyiodo)arenes bearing acid-sensitive Boc protecting groups (1i) and heteroaromatic moieties such as pyridyl (1j) and thienyl (1k) groups. The reaction of bis(diacetoxyiodo)arene (1l) with 1,3,5-trimethoxybenzene (2.1 equiv) under the same

• , consequently yielding the desired products in high yields. However, the common synthetic methods of diaryliodonium(III) triflates involving a strong oxidizing agent with a strong acid and an electron-rich arene often resulted in black/discolored products, indicating decomposition, poor yields, and lower

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• distance between the ortho substituents d is slightly larger in 1,5-BCH than in ortho-benzene (Figure 7) [42]. The substituent–arene angles φ2 and φ3 are similar, but the dihedral angle θ between substituents is necessarily larger in 1,5-BCHs than the near 0° angle for ortho-benzenes. Mykhailiuk and co

• ester 136g. The latter could then be oxidised to the corresponding alcohols 137f–g. The bridgehead iodine substituent could also be harnessed in iron-catalysed Kumada coupling reactions to furnish a larger number of arene-substituted 1,5-BCHeps 138. Anderson and co-workers also reported access to

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

Mono or double Pd-catalyzed C–H bond functionalization for the annulative π-extension of 1,8-dibromonaphthalene: a one pot access to fluoranthene derivatives

• Nahed Ketata,
• Linhao Liu,
• Ridha Ben Salem and
• Henri Doucet

Beilstein J. Org. Chem. 2024, 20, 427–435, doi:10.3762/bjoc.20.37

• cycle involves the oxidative addition of 1,8-dibromonaphthalene. Then, a concerted metalation–deprotonation of the arene, which usually occurs at the ortho-position of an activating group such as a fluorine or a chlorine atom, followed by reductive elimination, gives the corresponding intermediate 1

• reported [39][40]. The synthesis of fluoranthenes from 1,8-dibromonaphthalene via a double C–H bond activation of the arene used as coupling partner remains limited to specific arenes featuring an activated C–H bond. Consequently, we also investigated the access to fluoranthenes from 1,8-dibromonaphthalene

• simplest involves 1,8-dibromonaphthalene with a double C–H bond functionalization of benzene derivatives. This method, which employs Pd-catalyzed intermolecular and then intramolecular activation of arene C–H bonds, tolerates several useful substituents on the arene, such as fluoro, chloro, methoxy

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

• , such as camphorsulfonic acid (CSA) [44], diammonium hydrogen phosphate (DAHP) [45], Amberlyst 15 [46], P2O5/MeSO3H [47], p-sulfonic acid calix[4]arene [48], xanthan sulfuric acid (XSA) [49], H5PW10V2O40/pyridino-santa barbara amorphous-15 (SBA-15) [50], TiO2-SO42− [51][52], humic acid [53] or Lewis

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• arene–oxanorbornadiene annulation reactions [40]. This study involved converting PAHs obtained through annulation and aromatization steps into curved PAH structures using metal-catalyzed cycloaddition reactions pioneered by Vollhart [41] and Kotora [42]. Unlike previous studies that reported

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

• Karolis Leitonas,
• Brigita Vigante,
• Dmytro Volyniuk,
• Audrius Bucinskas,
• Pavels Dimitrijevs,
• Sindija Lapcinska,
• Pavel Arsenyan and
• Juozas Vidas Grazulevicius

Beilstein J. Org. Chem. 2023, 19, 1867–1880, doi:10.3762/bjoc.19.139

• ) ethynyltrimethylsilane (2 equiv), PdCl2(PPh3)2 (0.07 equiv), CuI (0.05 equiv), diisopropylethylamine, DMF, 55 °C, 12 h; e) K2CO3 (2 equiv), MeOH/Et2O, 1 h; f) Pd(PPh3)4 (0.1 equiv), CuI (1 equiv), DMF/DIPEA, 80 °C, 48 h. Synthesis of dicyanocarbazoles 7–9. Reaction conditions: a) corresponding ethynyl arene, Pd(Ph3P)4

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• slightly enhanced upon complexation. Crowned calixpyrroles In 2008, Sessler and co-workers synthesised an ion-pair receptor incorporating a calix[4]pyrrole framework functionalised with the crown ether units attached through meso-aryl groups (Scheme 1) [101]. The system comprised a crown-6-calix[4]arene

• -capped calix[4]pyrrole cavitand 4. The heteroditopic receptor had multiple binding sites, proving efficient in encapsulating a CsF ion pair. The calix[4]arene-crown-6-capped pocket was exploited as an excellent binding site for the Cs+ cation, whereas the calix[4]pyrrole was aligned to trap the fluoride

• separation between the cation and anion. Sessler and co-workers introduced a similar ion-pair receptor, in which the calix[4]arene-strapped calix[4]pyrrole 5 demonstrated an additional binding mode of CsF (Figure 5). The binding constant Ka = 1.3·104 M−1 in CHCl3/MeOH 9:1 was reported [101][102]. This

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• exchange and dispersion interactions in CHCl3 in relation to DMSO are the driving forces behind the placement of sec-amine molecules into the R[4]A cavity and the formation of “in” type complexes. Keywords: complexes; DFT calculations; hydrogen bond; resorcin[4]arene; supramolecular chemistry

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• of aryl sulfides by using the catalyst and the base. A catalytic cycle is shown in Scheme 4. Firstly, electrophilic Pd(TFA)2 generated from Pd(OAc)2 and TFA, which (by C–H functionalization of arene 4) led to intermediate II. Oxidative insertion of intermediate II into the N–S bond of 1 afforded

• , and TMSOTf resulted in good chemical yields. In the transformation, the selectivity of the endo or exo cyclization depended on the atom number of the chain between alkene and arene, leading to the formation of 6-, 7-, or 8-membered rings. In addition to N-(thio)phthalimides, benzenesulfenyl chloride

• an effective catalysis system (Scheme 29) [63]. Kinetic studies in this cross coupling-reaction indicated that N-(arylthio)succinimides 1 with electron-deficient arene 4 undergoe thioarylation catalyzed by Fe(NTf2)3. Related molecules bearing an electron-rich arene showed an autocatalytic pathway

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

• resulting in two different ligand coupling outcomes. While most of their reactions expel an iodoarene to produce functionalized β-dicarbonyl motifs, ligand coupling with the arene motif is also possible, such as in the (radio)fluorination of iodonium ylides. Finally, intramolecular σ-hole bonding offers the

• halogen bonding had been invoked for years when describing reactions of such ylides. In 2022, Murphy et al. used computational analysis to assess iodonium ylides for their σ-holes, and found that two of these existed, with one situated opposite the arene and the other opposite the β-dicarbonyl motif

• (Figure 4) [100]. In the dimethyl malonate-derived ylide I-10, the σ-hole opposite the β-dicarbonyl was stronger with an electrostatic potential of 0.084 e, compared to the 0.049 e found for that opposite the arene. The same pattern was observed for the acetylacetone-derived ylide I-11, which possessed

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

• (pinacolato)diboron (B2pin2) as trapping agents for C(sp2)–Het(Arene) couplings (Figure 9B). The successful activation of electron-neutral and electron-rich aryl halides via conPET mostly remained an unsolved challenge until the Nicewicz group in 2020 disclosed a modified acridinium (Fukuzumi) salt Mes-Acr

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• bond formed between the imine nitrogen of 49 and the catalyst’s OH group (see transition state 84). These dual H-bonding interactions were assisted by a π–π interaction between the arene rings of both the electrophile and nucleophile that helped in the formation of a stereodefined transition state. The

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• ][43][44][45]. On the other hand, a metal-catalyzed functionalization of arene/heteroarene C–H bonds to the corresponding C–C bonds is an area of great interest and has been well studied [46][47]. Pyridine, being an important heterocyclic scaffold, various studies have been conducted for the C(sp2)–H

• -substitution, however, the authors found that the yield of the meta (C-3)-arylated pyridines were drastically higher, thereby showcasing the regioselectivity of the reaction. The chelating anionic ligand acted as base in the catalytic cycle, allowing for the oxidative addition of the arene to the Pd complex

• the bi(hetero)arene–Pd(II) species 177 which undergoes reductive elimination furnishing the desired products 174/175. C–H Annulation of pyridine to fused heterocycles Annulation reactions in organic synthesis have achieved great attention toward the construction of various carbocycles and heterocycles

Palladium-catalyzed enantioselective three-component synthesis of α-arylglycine derivatives from glyoxylic acid, sulfonamides and aryltrifluoroborates

• Bastian Jakob,
• Nico Schneider,
• Luca Gengenbach and
• Georg Manolikakes

Beilstein J. Org. Chem. 2023, 19, 719–726, doi:10.3762/bjoc.19.52

• situ generation of reactive imine species, we have disclosed iron- and bismuth-catalyzed three-component reactions for the synthesis of α-arylglycines [14][15][16], in which the arylboronic acid could be replaced with an electron-rich (hetero)arene as nucleophile. In parallel, we have developed

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• received considerable attention in recent years. Several different arene and directing groups have been investigated; however, they typically result in the exo-selective addition product with the bridge heteroatom intact. Although this limits the applicability of the reaction, the authors noted the use of