Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• synthetic strategy. The tandem Suzuki coupling/Knoevenagel condensation strategy leading to PAH 85 was independently reported by Liu [61] and Mastalerz (Scheme 12) [62]. The first group reported a cascade formal [3 + 4] annulation between triple boronic ester 83 and naphthalene 84 which combines a Suzuki

Studies on the syntheses of β-carboline alkaloids brevicarine and brevicolline

• Benedek Batizi,
• Patrik Pollák,
• András Dancsó,
• Péter Keglevich,
• Gyula Simig,
• Balázs Volk and
• Mátyás Milen

Beilstein J. Org. Chem. 2025, 21, 955–963, doi:10.3762/bjoc.21.79

• brevicarine (2) could not be detected by LC–MS. As regards our plans for an alternative synthesis of racemic brevicolline ((±)-1), our primary goal was the direct coupling of the pyrrole ring to compound 3, instead of its ring-closing construction shown in Scheme 1. Suzuki reaction of 3 with pyrrole boronic

• ester 29 gave pyrrolo-β-carboline 30 in excellent yield (Scheme 7). Our attempts for the selective saturation of the pyrrole ring of 30 by catalytic reduction were unsuccessful. When the hydrogenation was carried out under mild conditions (ambient temperature, 15 bar H2) in the presence of PtO2.H2O

Recent advances in allylation of chiral secondary alkylcopper species

• Minjae Kim,
• Gwanggyun Kim,
• Doyoon Kim,
• Jun Hee Lee and
• Seung Hwan Cho

Beilstein J. Org. Chem. 2025, 21, 639–658, doi:10.3762/bjoc.21.51

• electronegativity, reaching 1.648 Å in the reactive alkoxytrialkyl complex D and 1.659 Å in the tetraalkyl "ate" complex E. The B–C bond lengths in amido- and alkyl-substituted boronic ester complexes B and C fell between these extremes, suggesting an intermediate level of activation. These findings prompted

• -diborylalkanes 47 using an H8-BINOL-derived phosphoramidite ligand L5, achieving exceptional enantiocontrol (Scheme 16) [59]. Their studies revealed the critical role of both the alkali metal cation and boronic ester moiety. While LiOt-Bu provided excellent enantioselectivity (er = 95:5), NaOt-Bu and KOt-Bu

Synthesis of acenaphthylene-fused heteroarenes and polyoxygenated benzo[j]fluoranthenes via a Pd-catalyzed Suzuki–Miyaura/C–H arylation cascade

• Merve Yence,
• Dilgam Ahmadli,
• Damla Surmeli,
• Umut Mert Karacaoğlu,
• Sujit Pal and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2024, 20, 3290–3298, doi:10.3762/bjoc.20.273

• ] or catechol [47] boronic esters as the final products. Therefore, it is important that they can be directly utilized with our methodology without further boronic ester interconversions. To this end, we first tested the reaction of thiophene-3-ylboronic acid pinacol ester (17b), and we were pleased to

• ). Finally, due to our interest in the structural features and chemistry of 1,8-dihydroxynaphthalene (1,8-DHN) [48][49], we were curious to check the reactivity of the previously unknown boronic ester 17d, which was prepared in one step from thiophene-3-ylboronic acid (17a) and 1,8-DHN [50]. Note that

• boronic esters of 1,8-DHN have recently been investigated and reported by Krempner and co-workers [51]. To our delight, the Suzuki–Miyaura coupling/intramolecular C–H arylation sequence between 12 and boronic ester 17d proceeded smoothly affording product 15a in 84% yield. The results summarized in Table

Germanyl triazoles as a platform for CuAAC diversification and chemoselective orthogonal cross-coupling

• John M. Halford-McGuff,
• Thomas M. Richardson,
• Aidan P. McKay,
• Frederik Peschke,
• Glenn A. Burley and
• Allan J. B. Watson

Beilstein J. Org. Chem. 2024, 20, 3198–3204, doi:10.3762/bjoc.20.265

• chromene (12) were tolerated. Benzylic azides were accommodated including those bearing nitro (2), iodo (3), and boronic ester groups (5, 21). Strained rings were effective including cubane (18) and bicyclopentane (20). While 18 and 20 were isolated in lower yield, no evidence of ring opening was observed

C–C Coupling in sterically demanding porphyrin environments

• Liam Cribbin,
• Brendan Twamley,
• Nicolae Buga,
• John E. O’ Brien,
• Raphael Bühler,
• Roland A. Fischer and
• Mathias O. Senge

Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234

• porphyrins appended with boronic ester groups to be structurally disseminated by X-ray crystallography [62][63]. Compound 46 was found to crystallize in a 1:1 ratio with bis(pinacolato)diboron, with a void size of 8–9 Å. The formation of channel-type lattice structures is thermodynamically unfavorable, when

Chemo-enzymatic total synthesis: current approaches toward the integration of chemical and enzymatic transformations

• Ryo Tanifuji and
• Hiroki Oguri

Beilstein J. Org. Chem. 2024, 20, 1693–1712, doi:10.3762/bjoc.20.151

• Suzuki–Miyaura coupling with boronic ester 53 and O-acetylation furnished 54. The dienophile component, morachalcone A (44), was synthesized from phenol 55 in four steps including O-prenylation and subsequent Claisen rearrangement, aldol condensation with 56, and deprotection. The key chemo-enzymatic

(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

• rearrangement, amine (±)-27 was then accessible in one additional step. Formation of redox active ester (±)-28 from acid (±)-26 allowed photochemical Minisci reaction to 1,2-BCH (±)-29 and borylation to boronic ester (±)-30. Synthesis of phenol isostere (±)-31 was possible through oxidation of boronic ester

• synthesis of some 1,5-BCHeps, including 134b, was also possible on mmol scale. Through derivatization of iodine-substituted 1,5-BCHeps 134f and 134g, an even larger number of 1,5-BCHeps were accessed (Scheme 14B) [27][47]. For example, lithium–halogen exchange was used to prepare acids 135f–g and boronic

• 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

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• dimerization of radical 76. Reaction between radical 9 and species 78 affords boronic ester 79 while returning boryl radical 76. Finally, chain propagation takes place via reaction of 76 with another equivalent of the NHPI ester 3. The Baran lab has recently published a complementary electrochemical method

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• -N-carbazole 2 in good yield (87%). Compound 2 was then converted to the boronic ester intermediate 3 in 41% yield over two steps: monobromination at the carbazole unit of 2 with NBS/THF at low temperature giving the unisolated mixed brominated product followed by borylation with bis(pinacolato

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

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• in catalysis beyond their typical use as Lewis acids [46]. This strategy has allowed the synthesis of bench-stable boronic ester products, rather than sensitive alkylboranes, and enabled the use of substoichiometric amounts of enantioenriched boron reagents, which can be challenging to prepare. This

• [58]. The alkyne 1 and dialkylborane reacted to give an alkenylborane 2. Transborylation with HBpin gave the alkenyl boronic ester 3 and regenerated the catalyst, HBR2. Isotopic labelling (H10Bpin) confirmed B–C(sp2)/B–H transborylation proceeded by σ-bond metathesis, and not ligand exchange. Using

• allene 14, giving a boryl diene 16. A Cope rearrangement of the boryl diene 16 followed by transborylation gave the dienyl boronic ester 18 and regenerated the catalyst (Scheme 5). Chang reported the alkoxide-promoted hydroboration of N-heteroarenes with HBpin, the first explicit example of a B‒N/B‒H

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• derivative of 31 could be isolated; it hydrolysed on the column back to the starting material. Thus, after reacting 31 with n-butyllithium and trimethyl borate, the obtained species was reacted in situ with pinacol to generate the corresponding boronic ester 32, which could be isolated by column

Borylated norbornadiene derivatives: Synthesis and application in Pd-catalyzed Suzuki–Miyaura coupling reactions

• Robin Schulte and
• Heiko Ihmels

Beilstein J. Org. Chem. 2022, 18, 368–373, doi:10.3762/bjoc.18.41

• catalyst and additive. The 1H NMR-spectroscopic analysis of the reaction showed that in both attempts no reaction occurred. It may be concluded that the nucleophilicity of the boronic ester is not sufficient, however, under the employed conditions, it can be hydrolyzed to the more reactive boronic acid

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• molecules 1f–j (Figure 1) were synthesized by a modular approach described by Heitmann et al. [15]. The boronic ester 22 was prepared according to a mixed aldehyde procedure [16][17] and the substituted azopyridines 14, 18, 20, and 21 were attached using Suzuki conditions. Synthesis of azopyridines 10–12

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• biocompatibility while remaining fluorescent. Keywords: ball milling; boronic ester; dextran; bodipy; nanoparticles; Introduction In the last few decades, mechanochemistry has gathered a great deal of attention and a lot of efforts have been focused on its use in organic synthesis, catalysis, biotransformation

• properties of BODIPY and the biocompatibility of dextran. The BODIPY dextran nanoparticles were characterized regarding their size, morphology, polarity, and toxicity in vitro. We demonstrate the feasibility of mechanochemistry for boronic ester formation [23] to a glycan polymer as a route of conjugation

Synthesis of 3-substituted isoxazolidin-4-ols using hydroboration–oxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles

• Lívia Dikošová,
• Júlia Laceková,
• Ondrej Záborský and
• Róbert Fischer

Beilstein J. Org. Chem. 2020, 16, 1313–1319, doi:10.3762/bjoc.16.112

• -hydroxyisoxazolidines by the treatment of boronic ester-substituted isoxazolidines with basic hydrogen peroxide has previously been described [30][31]. To start with, the phenyl-substituted 2,3-dihydroisoxazole 5a was chosen as the starting substrate. After optimizing Kang's reaction conditions in terms of the borane

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• % aqueous NaOH in the presence of tetrabutylammonium iodide (TBAI) [33][34][35]. Upon chromatography 3-bromo-9-hexylcarbazole (4) was obtained as a liquid in good yield. 3-Bromo-9-hexylcarbazole (4) was then converted into the pinacol boronic ester by treating with bis(pinacolato)diboron in the presence of

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• 96 h. The aryl (i.e., 133), ether (i.e., 140a), ester (i.e., 140b), tert-butyldimethylsilyloxy (i.e., 140c), boronic ester (i.e., 140d), acetal (i.e., 140e), and indol products (i.e., 140h) of various bromo-substituted starting materials were successfully obtained. For 1-bromo-3-chloropropane, the

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• regioisomeric bromides were also formed, but they were separated by column chromatography on the next step. Bithiophene 11 was prepared in 74% yield by using a Suzuki–Miyaura coupling (catalyzed by PEPPSI-IPr) between boronic ester 9 and bromide 10 [13][14]. Boronation of bithiophene 11 was achieved under

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• irreversible precipitation of a product, and an inevitable shift in dynamic equilibrium. Several types of reversible reactions have been successfully employed in the formation of DCL, including transesterification, peptide bond exchange, disulphide exchange, olefin metathesis and boronic ester formation [189

Norbornadiene-functionalized triazatriangulenium and trioxatriangulenium platforms

• Roland Löw,
• Talina Rusch,
• Tobias Moje,
• Fynn Röhricht,
• Olaf M. Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1815–1821, doi:10.3762/bjoc.15.175

• obtained in a convergent synthesis (Scheme 2). Boronic ester 9 was synthesized as described in the literature [15]. In a Suzuki cross-coupling reaction norbornadiene 4 was coupled with 9 to the extended norbornadiene 10 (38%), which was attached to the TATA platform 6 to yield the extended norbornadiene

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• the oxiranyllithium species upon the addition of the boronic ester. Unfortunately, all attempts to detect or isolate such ate complexes or related oxiranylboronic esters failed so far [38]. The oxiranylborate complex B then undergoes an intramolecular SN2-like process (Matteson-type rearrangement) [14

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

• Daniela Imperio,
• Erika Del Grosso,
• Silvia Fallarini,
• Grazia Lombardi and
• Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

• about the solution behavior of these compounds we performed MS analysis. The mass spectrum of compound 8 in aqueous solution showed the presence of the cyclic boronic ester both in the positive ionization mode, as adduct at m/z 180 ([M + NH4]+) and m/z 185 ([M + Na]+), and in the negative ionization

• suitable for future biological tests. Conclusion In conclusion, we have reported the synthesis, stability evaluation, and preliminary biological testing of two sugar analogues bearing a boron atom at the anomeric position. Compound 8 showed a tendency towards elimination reaction, probably through boronic

• ester ring opening, while compound 11 demonstrated to be stable. The two compounds showed no toxicity on human primary fibroblasts. Further studies will be conducted to determine the cellular uptake of compounds 8 and 11. Structure of boronic acid analogues (for clarity, sugar numbering has been

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• -workers (Figure 10). Under ball-milling conditions (20 Hz), the condensation of 4-formylphenylboronic acid, pentaerythritol and 1,3,5-tri(aminomethyl)-2,4,6-triethylbenzene afforded 94% of sphere-like compound 21 in 1 h [63]. In 2018, Wang and co-workers also demonstrated the synthesis of boronic ester

• -containing [2]rotaxanes [61]. Mechanochemical liquid-assisted one-pot two-step synthesis of [2]rotaxanes under high-speed vibration milling (HSVM) conditions [62]. Mechanochemical (ball-milling) synthesis of molecular sphere-like nanostructures [63]. High-speed vibration milling (HSVM) synthesis of boronic

• ester cages of type 22 [64]. Mechanochemical synthesis of borasiloxane-based macrocycles. Mechanochemical synthesis of 2-dimensional aromatic polyamides. Nitschke’s tetrahedral Fe(II) cage 25. Mechanochemical one-pot synthesis of the 22-component [Fe4(AD2)6]4− 26, 11-component [Fe2(BD2)3]2− 27 and 5