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

• ) reported by Arduengo et al. [3], turned out to be a watershed in this regard as it initiated intense research activity in this field. Compound 6 is stable in the absence of oxygen and air. The first air-stable carbene, namely 1,3-dimesityl-4,5-dichloroimidazol-2-ylidene (7b) [4] was obtained from the

• ). The complexes were obtained in high yields (>95%). The copper complexes were air and moisture-stable as solids but decomposed in chlorinated solvents after several days. It may be mentioned that Cu(I) halide and pseudohalide complexes with NHCs Me2L, Et2L and AdL were prepared from direct reaction of

• NEt3·3HF, AgHF2 could also be used. The complexes were found to be air-stable in the solid state and moderately stable in solution. They were unambiguously characterized on the basis of NMR studies including 19F NMR and X-ray crystal analysis. With the IMes ligand, an air-stable bis(NHC)Cu(I) complex

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

• method was developed for the incorporation of the phosphocholine polar head group that makes use of the phosphoramidite 8.2 which is a weakly air sensitive reagent [85]. This method was applied for the synthesis of PAF as illustrated in Figure 8 [86]. The alcohol 8.1 reacted with 8.2 in the presence of

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

• aerated MCH solution. The reduction in quantum yield on exposure to oxygen is due to quenching of the triplet excited states indicating a TADF luminescence mechanism. PLQY in Zeonex films is 39% in air, which is lower than the PLQY of 87% reported for 4CzIPN [17]. The two-component excited state lifetime

• GCE was left to air dry and residual traces of water were removed under vacuum. The Ag wire pseudoreference electrodes were calibrated to the ferrocene/ferrocenium couple in THF at the end of each run to allow for any drift in potential, following IUPAC recommendations [16]. All electrochemical

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

• the substrate achieved the activation of the C(sp2)–H bond. Other non-noble metal-catalyzed reactions In 2013, Liu et al. reported that MnO2 could catalyze the CDC of the benzylic C(sp3)–H bond in benzyl ethers with α-carbonyl C(sp3)–H bonds in the presence of air at room temperature (Scheme 33) [98

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

Selective and scalable oxygenation of heteroatoms using the elements of nature: air, water, and light

• Damiano Diprima,
• Hannes Gemoets,
• Stefano Bonciolini and
• Koen Van Aken

Beilstein J. Org. Chem. 2023, 19, 1146–1154, doi:10.3762/bjoc.19.82

• byproducts, and increased efficiency in industrial processes. As such, this field of research is of great importance and interest to both academia and industry. This work showcases a sustainable and catalyst-free oxidation method for heteroatoms (e.g., S, P, and Se) using only air, water and light. An

• selectivity and safety. Traditional oxidants, such as Oxone, CrO3, NaIO4, or KMnO4, produce significant amounts of toxic waste, exacerbating these issues (Scheme 1A) [1]. As environmental concerns and economic factors increasingly affect chemical processes, hydrogen peroxide and oxygen (or air) are becoming

• ) [2][3][4]. Additionally, practical implementation of hydrogen peroxide can be challenging due to requirements for precise dosing to avoid issues such as dismutation, overoxidation, and catalyst degradation [5]. In this respect, oxygen, or preferably air, represents a better alternative to traditional

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

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• fluorescence under nitrogen atmosphere and a substantial quenching under air or oxygen atmosphere [22], the fluorescence spectra of the dyads containing native PTZ unit under different atmospheres were studied (Figure 3a–d and Figure S32a in Supporting Information File 1). The results show that the

• fluorescence intensity of the dyads is stronger under a N2 atmosphere, but is significantly quenched under air atmosphere. The fluorescence intensity under N2 atmosphere is 2–4 times higher than that under an air atmosphere. However, for the dyads with an oxidized PTZ unit (Figure 3e and 3f and Figure S32b in

• Supporting Information File 1), the fluorescence intensity is less dependent on the atmosphere. Moreover, we suggest that the reduced luminescence of the oxidized molecules in air may be caused by the quenching effect of oxygen to the S1 state. According to this experimental phenomenon, we preliminarily

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• 2013, Zhang and co-workers [67] reported the preparation of a new recyclable magnetic nanoparticle-supported antimony catalyst (γ-Fe2O3@SiO2-Sb-IL) and its application in the filtration-free, Clauson–Kaas synthesis of N-substituted pyrroles. This catalyst is fairly easy to make, air stable, and

A fluorescent probe for detection of Hg²⁺ ions constructed by tetramethyl cucurbit[6]uril and 1,2-bis(4-pyridyl)ethene

• Xiaoqian Chen,
• Naqin Yang,
• Yue Ma,
• Xinan Yang and
• Peihua Ma

Beilstein J. Org. Chem. 2023, 19, 864–872, doi:10.3762/bjoc.19.63

• mol·L−1 hydrochloric acid solution, heated at 70 °C, cooled and filtered. The filtrate was slowly evaporated in air (about 10 days) to obtain colorless crystals. Ultraviolet–visible absorption and fluorescence spectroscopy An aqueous solution of TMeQ[6] and G@TMeQ[6] at 3.0 × 10−5 mol L−1 was prepared

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions

• Masahiro Hosoya,
• Yusuke Saito and
• Yousuke Horiuchi

Beilstein J. Org. Chem. 2023, 19, 752–763, doi:10.3762/bjoc.19.55

• , which diminishes the atom economy [2]. To overcome this limitation, the use of molecular oxygen (O2) present in air as an oxidant is one of the ideal solutions [10][11]. The reduction of O2 generates only water as a byproduct, leading to high atom-economy processes. However, the use of O2 as an oxidant

• air was switched to an O2 balloon to increase the partial pressure of O2 (Table 2, entry 1 vs 2 and 3 vs 4). At room temperature, the reaction rate did not increase although the partial pressure of O2 increased approximately five times with this change. In contrast, at 60 °C, the reaction rate

• the solubility of O2, is not the rate-determining step. Therefore, the reaction rates under open air and O2 balloon did not differ. On the other hand, increasing the temperature decreased the solubility of O2, which converted the catalytic cycle A to the rate-determining step at 60 °C. When the

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

• to the formation of the arylgylcine in trace amounts (Table 1, entries 2–5). Contrary to our previous report with arylboronic acids, the presence of air is highly detrimental to the reaction outcome (Table 1, entry 6). Therefore, inert conditions were employed throughout all subsequent studies

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

• using air as the sole oxygen source. Keeping in mind the progress in photochemical relay catalysis [24] and the attention paid to photocatalytic carbon-bond functionalization in the past several years [25], here we developed an organophotoredox-catalyzed C–H functionalization of imidazo[1,2-a]pyridines

• functionalizations of IPs and present work. Substrate scope. Conditions: unless otherwise noted, all reactions were carried out with 1 (0.2 mmol), 2 (0.4 mmol), PTH (5 mol %), Zn(OAc)2 (0.6 mmol), dry 1,2-DCE (2 mL), irradiation with LEDs (λmax = 390 nm), under air for 10 h. Mechanistic investigations. Plausible

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• at the liquid–air interface, testing solutions with a 2 mL volume were used. Fluorescence and CD spectra were recorded using appropriate 1 cm path quartz cuvettes; UV–vis spectra were recorded in 1 cm path quartz cuvettes or using an immersion probe with 5 cm light path length. Isothermal titration

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

• air or moisture sensitive). Under these mild reaction conditions, a panel of α-(hetero)arylacrylamides were trifluoromethylthiolated in good to high yields. Acrylamides substituted at the α-position by an aryl bearing an electron-donating group (OMe) or halogen (Cl) at the para-position were readily

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

• milling the ligand precursor 1 with metallic copper powder in air [45]. Another mechanochemical pathway was published using K2CO3 as a base and copper(I) chloride [46][47]. This latter procedure is practical, avoids the use of solvents, and relies on an abundant and cheap base. We have recently disclosed

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• and the isomeric corniculatolides. The isolation of the compounds was achieved from 5 kg of air-dried bark of the aforementioned tree, which was grounded and then extracted with CHCl3 using a Soxhlet apparatus, furnishing 32.0 g of the crude extract. This extract was subjected to a vacuum liquid

• Indian Ocean coastline. The air-dried stems of X. granatum (5 kg) were powdered and extracted successively within hexane, CHCl3, and acetone in a Soxhlet apparatus. The crude CHCl3 extract (21 g) was chromatographed on silica gel (230–400 mesh) vacuum liquid chromatography (VLC) in different gradients of

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

• , rt, 24 h, aq PF6−, (iii) CoCl2∙6H2O, THF/acetone, rt, air bubbling, overnight, (iv) KBr, THF/acetone, rt, 5 d. Synthesis of triazole-linked porphyrin-bearing N-doped graphene hybrid 96. Synthesis of meso-triazole-linked porphyrin-fullerene dyads 100a–d and 104a,b. Synthesis of meso-triazole-bridged

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• ][9]. Metathesis reactions take place by the means of a metallic catalyst. Firstly, olefin metathesis was achieved with an air-sensitive tungsten complex [8]. An important focus on air-stable catalyst design was undertaken and contributed to the popularization of the reaction. Thus, Grubbs catalysts

Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic liquids (TAAILs)

• Swantje Lerch,
• Stefan Fritsch and
• Thomas Strassner

Beilstein J. Org. Chem. 2023, 19, 212–216, doi:10.3762/bjoc.19.20

• presented by Wilke and colleagues in 1986 [17]. At that time, chloroaluminate ionic liquids were used both as a solvent and catalyst [18][19], but these systems proved to be unstable under ambient air conditions and prone to decompose in the presence of water [20]. In the following years, ionic liquids

• cost-efficient metal salts in a water and air stable ionic liquid is still hard to find [50][51]. In this contribution, we present the use of imidazolium-based tunable aryl alkyl ionic liquids (TAAILs) in a catalytic Friedel–Crafts acylation. This relatively new class of ionic liquids [52] previously

• robust system for a catalytic Friedel–Crafts acylation. The reaction was carried out at moderate temperatures of 40 °C to 60 °C under air, was scalable to gram-scale and tolerated different electron-rich benzene derivatives as well as anhydrides. The catalytic performance depends on the choice of ionic

Nostochopcerol, a new antibacterial monoacylglycerol from the edible cyanobacterium Nostochopsis lobatus

• Naoya Oku,
• Saki Hayashi,
• Yuji Yamaguchi,
• Hiroyuki Takenaka and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2023, 19, 133–138, doi:10.3762/bjoc.19.13

• ), or Dok Hin (stone flower) [11]. It is consumed as an ingredient of salad and as a folk medicine to treat pain from stomach ulcers or fever [9]. In fact, an ethanolic extract of the air-dried alga was found to inhibit the development of gastric ulcers, suppress ethyl phenylpropiolate-induced edema on

Preparation of β-cyclodextrin/polysaccharide foams using saponin

• Max Petitjean and
• José Ramón Isasi

Beilstein J. Org. Chem. 2023, 19, 78–88, doi:10.3762/bjoc.19.7

• . The second process (45spFoam*) consists of introducing 20 mL of the stock solution into a large crystallizer, where the liquid height reaches around 1 cm. The liquid is stirred during 5 min at high speed to make an air/water emulsion. The resulting foam is quickly frozen at −40 °C, lyophilized

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• synthesis of tridachiapyrone B was not investigated, even though it seems conceivable that the compound’s stability to light, air or cytochrome would be higher than its 1,3-cyclohexadiene counterpart. As the molecule combines electron acceptor functions such as α’-methoxy-γ-pyrone and 2,5-cyclohexadienone

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• crude product is mixed with a carrier solvent and an air flow to generate a gas–liquid flow pattern. This is then directed into three different coils held at different temperatures where the solid product precipitates in a controlled manner prior to isolation by filtration. As the same solvent is used

• crystallization procedure regardless of the manufacturing scale [117]. An air-segmented flow crystallizer was developed by Cooks and co-workers for the synthesis and purification of diphenhydramine [118]. In this study ethyl acetate was used as antisolvent and careful control of nitrogen flow (used to obtain

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• include their synthetic availability, wide opportunities for rational structure design, generally lower toxicity, air and water stability, metal-free nature, and the scalability of their production and use. These features have made organocatalysis a prospering area and an even more promising methodology