Quinoxaline derivatives as attractive electron-transporting materials

• Zeeshan Abid,
• Liaqat Ali,
• Sughra Gulzar,
• Faiza Wahad,
• Raja Shahid Ashraf and
• Christian B. Nielsen

Beilstein J. Org. Chem. 2023, 19, 1694–1712, doi:10.3762/bjoc.19.124

• -withdrawing terminal acceptor units, and careful selection of solvents and annealing processes have also been demonstrated as potential solutions to improve charge transport and refine the device fabrication processes. You et al. found that the position of alkoxy side chains on the pendant benzene rings

• molecule series, Qx16, featured a 1,4-dihydro-2,3-quinoxalinedione core and different terminal acceptor units. The modified NFAs demonstrated visible and near-infrared absorption as well as good electron mobility, suggesting their potential for experimental exploration in (OCSs) [31]. While FREAs are

• compounds exhibited good coplanarity through intramolecular interactions, narrow bandgaps, broad absorption in the NIR region and PCEs above 10% [32]. Ayub et al. decorated the central donor–acceptor–donor unit of Qx17 and Qx18 with five new terminal end groups, resulting in the Qx19 series, and predicted

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

• configuration with dihedral angles of 54–56° between the planes of the terminal carbazole donors and the Nz acceptor that are beneficial for the state mixing between the LE and CT states. The lowest unoccupied molecular orbital (LUMO) was mainly localized on the Nz ring, while the highest occupied molecular

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• ATRP relies on the establishment of a reversible activation/deactivation equilibrium reaction between an alkyl halide or halide-like initiator (RX) and a radical species (R·) [43]. During the activation process, the organohalides quickly lose their terminal halogen atoms in the presence of the liganded

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• , which is an internal alkyne instead of a terminal alkyne, but no desired product was obtained. Next, we explored the substrate scope of 2-methylquinolines under the standard conditions. 2-Methylquinoline bearing different substituents at various positions gave the corresponding products with moderate to

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• , organic azides, and morpholine. Terminal gem-difluoroalkenes exhibit unique reactivity toward nucleophiles. The two σ-withdrawing fluorine atoms at the α-position and the strong polar nature of the double bond make gem-difluoroalkenes susceptible to a nucleophilic attack that is followed by a β-fluoride

Functions of enzyme domains in 2-methylisoborneol biosynthesis and enzymatic synthesis of non-natural analogs

• Binbin Gu,
• Lin-Fu Liang and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 1452–1459, doi:10.3762/bjoc.19.104

• studied. Several 2-methylisoborneol synthases have a proline-rich N-terminal domain of unknown function. The results presented here demonstrate that this domain leads to a reduced enzyme activity, in addition to its ability to increase long-term solubility of the protein. Furthermore, the substrate scope

• by two sequential cyclisation reactions to A and B, and terminal quenching with water. This hypothesis was confirmed by the discovery of the biosynthetic genes coding for a GPP methyltransferase (GPPMT) and a type I terpene synthase termed 2-methylisoborneol synthase (2MIBS) [23][24]. Interestingly

• versions of 2MIBSs exhibit a proline-rich N-terminal domain of unknown function that appears disordered in the crystal structure [28]. As a first aspect of this study, we have investigated the possible function of this N-terminal domain. 2MIBS is known to form several methylated monoterpenes as side

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• interesting to note that the levels of induction for the 1,4-addition–aldol condensations are somewhat higher than those obtained for the 1,4-additions. Aldehydes also proved competent terminal electrophiles for the tandem sequence. Illustratively, adducts 23 and 24 were obtained from α-(aminomethyl)acrylates

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• with alkynes under click chemistry conditions (Scheme 48) [15]. The products were obtained in high yields (93–99%). Cazin and co-workers systematically investigated the [3 + 2] cycloaddition of a series of six azides with seven terminal alkynes catalyzed by different 1,2,3-triazolylidene–CuCl complexes

• , generated from the tetranuclear complex, as the catalytically active species. 2.4 A3 reactions In recent years, the three component reaction of an aldehyde, a secondary amine and a terminal alkyne, known as A3 reaction to afford chiral propargylamines 140 has received much attention. The latter compounds

• diastereoselectivity (dr > 99:1) was observed in the reaction of chiral ketones. Hoveyda and co-workers [82] employed two types of NHC–Cu(I) complexes to catalyze the protoboration of terminal allenes to obtain vinylboranes (Scheme 60). A set of alkyl- and aryl-substituted allenes was used as substrates. The

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• azide was combined with a subsequent copper-catalyzed (3 + 2) cycloaddition with terminal alkynes. This one-pot process was developed with a simple model alkyne, but then applied to more complex alkynes bearing enantiopure 1,2-oxazinyl substituents. Hence, the precursor compounds 1,2-, 1,3- or 1,4-bis

• aminopyrans [54], should be converted into divalent compounds via coupling of the terminal propynyl group with benzylic biazides. Since biazides are potentially explosive [22] it was very desirable to avoid their isolation and to generate these reactive species in situ from the corresponding benzylic halides

Consecutive four-component synthesis of trisubstituted 3-iodoindoles by an alkynylation–cyclization–iodination–alkylation sequence

• Nadia Ledermann,
• Alae-Eddine Moubsit and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2023, 19, 1379–1385, doi:10.3762/bjoc.19.99

• generated by a consecutive four-component reaction starting from ortho-haloanilines, terminal alkynes, N-iodosuccinimide, and alkyl halides in yields of 11–69%. Initiated by a copper-free alkynylation, followed by a base-catalyzed cyclizive indole formation, electrophilic iodination, and finally

• prior to terminal alkylation could provide a straightforward entry to trisubstituted 3-iodoindoles, which are valuable building blocks for accessing highly decorated (aza)indoles (Scheme 1). Here, we report the concise consecutive four-component synthesis of trisubstituted 3-iodoindoles. Results and

• nitrogen protection or activation using KOt-Bu in DMSO as a base. Under these conditions, the formation of the terminal (aza)indole anion is the driving force (Scheme 1) [34]. As a consequence, the electrophilic trapping of this intermediate with alkyl halides provides as concise access to N-substituted

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• matrices regardless of numerous efforts and cooling the films down to 16 K and applying long time delays. Conclusion We have synthesized and characterized a donor–acceptor-type thermally activated delayed fluorescent emitter 4BGIPN with four terminal benzoguanidine donor moieties surrounding the

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• oxidative alkylation of cyclic benzyl ethers with malonates or ketones. Oxygen is used as a terminal oxidant at atmospheric pressure. The key intermediate of this oxidative coupling reaction is benzyl alcohol intermediate C (Scheme 4) [52]. The generation of N–O radicals from NHPI in the presence of oxygen

• triggers the whole coupling reaction. The potential application of NHIP as a catalyst for oxidative coupling reactions with oxygen as a terminal oxidant was explored. In 2011, Garcia-Mancheño et al. developed a Cu-catalyzed CDC of cyclic benzyl ethers 10 with aliphatic or α,β-unsaturated aldehydes 13 or 14

• terminal alkynes at room temperature (Scheme 15a) [67]. The ability to tune the reactivity of the trityl ion rationally improves the approach with excellent regio- and diastereoselectivity for the unsymmetric ethers. In 2018, Ye et al. reported a CDC reaction to form C(sp)–C(sp3) coupling products from

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

• molecular iron catalyst II and stoichiometric hydroxyiodinane as a terminal oxidant [38]. It is proposed that an azidoiodinane is generated in situ and serves as the radical initiator, generating an azido radical which adds to the less substituted position on the alkene. The resultant transient radical is

• , including terminal aliphatic alkenes, internal (cyclic) styrenes, and one example of a nonconjugated diene, suggesting RLT to be compatible with many functionalities. The diastereoselectivity of the reaction varies, with high anti-selectivity being achieved with cyclic styrenes and low diastereoselectivity

• the addition of terminal oxidant. II: The proposed mechanism includes reoxidation of the iron catalyst through inner-sphere electron transfer by anionic nitrate. Funding J.G.W. acknowledges financial support from CPRIT (RR190025), NIH NIGMS (R35GM142738), Research Corporation for Science Advancement

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

• SCE (1c) were readily reduced and dehalogenated products obtained in excellent yields (70–92%) (Figure 11A). Sodium formate was found to be a more efficient terminal reductant than trialkylamines which the authors attributed to the formation of a carbon dioxide radical anion (CO2•−) upon oxidation of

• -poor aryl halide substrates (Figure 11C). While trialkylamines like Et3N or DIPEA have been proven to be suitable terminal reductants in conPET chemistry [15][45][46][51][54], they may still decrease photoreductant activity via back electron transfer [56], in contrast to CO2•− which has an entropic

• catalyst generation for the reduction of aryl halides. Compared to conPET chemistry with organic photocatalysts, no terminal reductants like trialkylamines or formates were required for redox-neutral transformations like the C–H arylation, borylation or phosphorylation owing to the interplay between the

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

• after recrystallization. Subsequent ozonolysis of the terminal alkene functionality with a follow-up reduction furnished primary alcohol 134 which was transformed into the azide 135. Reduction of the azide 135 was accompanied by debenzylation, was followed by tosylation of the primary amine and exchange

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• formation of the terminal carboxamide in 6 might be due to a spontaneous C–N bond cleavage, which occurs in 1’’ prior to the cyclization, consistent with a mechanism recently proposed in photoxenobactin biosynthesis [34]. Despite the widespread occurrence of siderophores featuring a phenolic moiety with a

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

• Heck cross-coupling [69][70]. However, researchers have developed various methods for the transition-metal-catalyzed C(sp2)–H olefination using various types of alkenes as coupling partners [71][72][73]. This part of the review covers reports for the alkenylation of pyridine with terminal alkynes

• the pyridine ring in bipyridine ring systems. In early 2009 Miura and co-workers [111] reported the rhodium-catalyzed regioselective reaction of aryl-N-heterocycles and aromatic imines with terminal silylacetylenes 209 to synthesize C–H-alkenylated products 210. The terminal silylacetylenes were

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• recrystallization of the crude product from ethanol. Next, the oxidative dimerization of terminal alkynes 6a–e was carried out in an aerobic medium in the CuI/TMEDA/iPr2NH system at room temperature, which proved to be effective in the synthesis of butadiynes 1–4 [15] (Scheme 3). The desired diarylbutadiynes 5a–e

• of λmax is observed. On passing to oligomers 5d and 5e bearing strong electron-withdrawing CN and NO2 substituents in the benzene rings the picture changes. The π-deficient nature of the terminal aryl rings obviously facilitates their conjugation with π-excessive DMAN fragments. The λmax values and

• and 6b·HBF4. Since the UV–vis spectra of salts 11 are similar (even and especially in cases of methoxy and nitro derivatives 11e and 11b), it can be assumed that in all salts 11 the electron transfer from the terminal aryl to the central naphthalene rings takes place. Naturally, the more deficient the

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

• Phebox-based rhodium complex (C3) to catalyze the tandem conjugate addition of a terminal alkene followed by reacting the bicyclic dienol silyl ether intermediate with Michael acceptors in a one-pot procedure (Scheme 50) [92]. The bridged cyclic products 196a,b, formed by a double Michael addition

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• -pentafluoropropylphosphonate, bearing a trifluoromethyl and a difluoromethyl group is reported for the first time. Its application in CuI-catalyzed cyclopropanation reactions with aromatic and aliphatic terminal alkenes under mild reaction conditions is demonstrated. In total, sixteen new cyclopropanes were synthesized in

• difluoromethylphosphonate groups at the ring might be possible by using our newly developed bench-stable diazo reagent CF3C(N2)CF2P(O)(OEt)2. Therefore, we report herein our preliminary results toward this goal via copper iodide-catalyzed cyclopropanation reaction of an acceptor carbene precursor with selected terminal

• target diazo reagent 5, which contains both a trifluoromethyl and a difluoromethylphosphonate moiety, was isolated as a stable, non-volatile liquid (Scheme 2). To highlight the synthetic utility of the novel carbene precursor 5, subsequent [2 + 1] cycloaddition reactions with selected terminal aromatic

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

• -catalyzed borylalkynylation of oxabenzonorbornadiene (30b) with B2pin2 (53) and bromoalkynes 62 (Scheme 10) [44]. The scope of the reaction was limited to only two examples of bromoalkynes reacting with oxabenzonorbornadiene (30b). Notably, the yield of the reaction dramatically diminished when the terminal

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• common reaction conditions. The reaction has been defined by Houk and Rueping as a (3+ + 2) monopolar cycloaddition [33] pointing out the protonated state of the imino nitrogen of the hydrazone in contrast to the well-known 1,3-dipolar cycloaddition of azomethine imines in which the terminal nitrogen has

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• been shown to be active in a variety of reduction/hydrogenation transformations employing dihydrogen as terminal reducing agent. Keywords: ball mill; bifunctional catalysis; catalytic hydrogenations; copper; mechanochemical synthesis; N-heterocyclic carbenes; Introduction Prominent goals of green

• an ester reduction with H2 as terminal reducing agent utilizing bifunctional copper(I)/NHC complex 5 bearing a guanidine moiety as additional catalytic unit [48]. This catalyst acts by employing the copper(I)/NHC complex for H2 activation on the one hand and by using the guanidine subunit for

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• -dipolar cycloaddition reaction between an azide and a terminal alkyne, also popular as "click reaction" or CuAAC reaction. Moreover, the 1,2,3-triazole ring also serves as a spacer and an electron transfer bridge between the porphyrin and the attached chromophores. In order to provide a critical overview

• connect a porphyrin with a chromophoric group. Among these, the copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction [1][2] of azides with terminal alkynes is a popular and well established process to link a porphyrin with other moieties via 1,2,3-triazole group [3] (Figure 1). The term “click

• triazoloporphyrins 32a–c and triazole-bridged bisporphyrins 34 in good yields. The “click reaction” of azidoporphyrin 30 with the terminal alkynes 31a–c and 33 in a THF/water (3:1) mixture was investigated by using different catalytic systems. Among these, copper carbene (SIMes)CuBr proved to be a better catalyst