A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• tandem reaction proceeds via formation of a Schiff-base 39 and subsequently 1,3-dipolar cycloaddition to produce the intermediate 42. Then, the intermediate 42 affords the final product 43 via an oxidative aromatization process in the presence of air or iodine (Scheme 15). To propose a precise mechanism

•  24) [52]. A one-pot and multicomponent protocol for the synthesis of 5-selanyltriazoles 85 from the reaction of ethynylstibanes 82, organic azides 83, and diaryl diselenides 84 using catalytic amounts of CuI and 1,10-phenanthroline in DMSO at 60 °C under air with good to high yield was presented by

• aryl selenide anion to the antimony atom takes place to give 5-selanyltriazole 85 and Ph2Sb–SeAr. Ph2Sb–SeAr is hydrolyzed in aqueous medium to give selenol 90 and Ph2SbOH. Selenol 90 is oxidized in air and transformed into diselenide 84. Therefore, only 0.5 equiv of diaryl diselenide were necessary

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

• Feng Xiong,
• Bo Li,
• Chenrui Yang,
• Liang Zou,
• Wenbo Ma,
• Linghui Gu,
• Ruhuai Mei and
• Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

• , 3.0 equiv), Cu(OAc)2 (71 mg, 0.39 mmol, 1.30 equiv), and Na2CO3 (64 mg, 0.60 mmol, 2.00 equiv) under an air atmosphere. The mixture was stirred at 90 °C for 15 h. At ambient temperature, H2O (15 mL) and Et3N (0.5 mL) were added, and a suspension was formed immediately. After filtrated through a Celite

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• . Despite these disadvantages, this Fe(III) hydroalkylation could be carried out in air instead of an inert atmosphere usually required in gold methodologies. More recently, iridium complexes were used as efficient catalysts in intermolecular hydroalkylation reactions between β-diketones and less reactive

• could be conducted in an air atmosphere, and the reaction times were shorter using a combination of Fe(acac)3 and PhSiH3 as the reductor (Mukaiyama-like conditions) in the presence of an alkoxide source (Scheme 21) [79]. Under these conditions, the radical formed after the HAT with unactivated olefins

• (acetylacetonate) in the cross-coupling cycle. They achieved the desired cross-coupling products 89 with the reaction conducted in open air and under mild conditions (Scheme 35) [109]. Notably, the use of propylene carbonate as the co-solvent removed the need for inclusion of reductant or oxidant additives, such

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• , the first work on combining polyaromatic acceptor and heterocyclic donor fragments in one macromolecule on the isoindigo platform showed the possibility of designing one-component nonfullerene solar cells. The high stability of polymeric isoindigo in air, at elevated temperature, under redox

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• K2CO3 as a base; under these conditions, the best conversion of the starting materials and the highest yield (93%) for the expected product 9a were observed. Typically, for cycloadducts obtained from 1,4-naphthoquinone [38], the initially formed [3 + 2]-cycloadduct 10a smoothly underwent air oxidation

• ]-cycloadducts by air oxidation were isolated exclusively. Additionally, the X-ray structure of 9d is shown in Figure 2. Similar results were obtained starting with 1,4-anthraquinone (1b) and selected hydrazonoyl bromides 8. In this series, fused pyrazoles 9i–l were obtained in high yield (63–92%, Scheme 3

• trifluoroacetonitrile imines to give polycyclic pyrazole derivatives as exclusive products formed via spontaneous air oxidation of the initial [3 + 2]-cycloadducts. In contrast to some arylnitrile oxides and benzonitrile ylides, no competitive cycloaddition to the C=O bonds of the quinone molecule has been observed

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• [13]. For example, leaving them exposed to air leads to loss of the solvent and a brittle material that slowly loses its crystalline order. Solvates (II) may thus have played a role as intermediates. They may have formed while the dichloromethane content was still high, but may have given way to co

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• air- or water-sensitive compounds were conducted under an argon atmosphere. Argon gas was dried by passage through P2O5. Anhydrous THF and toluene were purchased and used as supplied. Silica gel 60N containing 0.5% fluorescence reagent 254 and a quartz column were used for column chromatography, and

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• before the introduction of GC–MS, and the elemental analysis of gases required special attention [55]. Guareschi also made the observation that air was necessary for the development of the gas, proposing a general scheme for the transformation that provides, however, no clue for a possible mechanism. In

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• delivered over a certain amount of time, yet a hydrophobicity for a long-term open-air application must be possessed in order to prevent the drying and a loss of a part [44]. Hydrophobic hydrogel is a novel concept that administers the surface properties of the initial network. In this section, we will

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• detected under air, further indicating a radical-initiated process was involved in the reaction (Table 1, entry 14). Under the optimal reaction conditions, we first evaluated the scope of N-arylallylamines for the synthesis of indolines. As shown in Scheme 2, substrates with various electron-donating

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• with sodium tetraarylboronates 64 was found to proceed with high diastereoselectivity under rhodium catalysis. Reddy and co-workers applied this methodology to the synthesis of 2-substituted pyrrolidines 66 [95]. The arylation of chlorinated imine (RS)-63 was performed with 2 mol % of an air-stable

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• 2011 [47]. The most efficient catalytic system was identified as a combination of (S)-t-Bu-PyOx (L9) with Pd(TFA)2 (Table 17). This system exhibited a remarkable tolerance for water and air. It was demonstrated by the addition of 10 equiv of water into the reaction mixture that caused only a very small

Enhanced target cell specificity and uptake of lipid nanoparticles using RNA aptamers and peptides

• Roslyn M. Ray,
• Anders Højgaard Hansen,
• Maria Taskova,
• Bernhard Jandl,
• Jonas Hansen,
• Citra Soemardy,
• Kevin V. Morris and
• Kira Astakhova

Beilstein J. Org. Chem. 2021, 17, 891–907, doi:10.3762/bjoc.17.75

• , placed on a slide and air-dried. Once dried, a small drop of Diamond Anti-Fade Mountant with DAPI (Invitrogen™, Thermo Fisher Scientific, MA) was added and a coverslip placed over the membrane. Slides were cured overnight at 4 °C before being visualized using a Zeiss Axio Vert A.1 light microscope with a

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• to the action of chemical (acids, air, halogens, solvents) or physical agents (heat, light). For polymers, the properties involved are, for instance, tensile strength, colour or shape, the change of which is usually associated with a modification of the chemical composition (e.g., as a consequence of

• products, such as coffee cups or take-away containers, can be recycled into videocassette cases or office equipment. Incineration at a temperature below 1000 °C and insufficient air is believed to produce a mixture of volatile compounds, including hazardous polycyclic aromatic hydrocarbons, alkylbenzenes

Breakdown of 3-(allylsulfonio)propanoates in bacteria from the Roseobacter group yields garlic oil constituents

• Anuj Kumar Chhalodia and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 569–580, doi:10.3762/bjoc.17.51

• the demethylation pathway that is fully established in P. inhibens by genes coding for DmdA–D (Scheme 4A). In the presence of air thiol 13 can then undergo an oxidative dimerization, or react analogously with MeSH to form allyl methyl disulfide (30, Scheme 4B). Similar oxidations requiring one

• index to the volatile 27 (Scheme 5B). This compound may arise from 23 by the action of an oxygenase that is restricted to O. indolifex and not encoded in the genomes of the other two species. Its spontaneous formation from 23 in the presence of air can be excluded, because other cultures forming 23 did

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

• Lucía Rossi-Fernández,
• Viviana Dorn and
• Gabriel Radivoy

Beilstein J. Org. Chem. 2021, 17, 519–526, doi:10.3762/bjoc.17.46

• the olefin to give π-bonded species of type B which could then lead to the formation of the corresponding epoxide product via the metalloepoxi species C [55][56]. On the other hand, considering that the reaction is carried out under air atmosphere, and that in the absence of TBHP the epoxidation also

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• synthesized for comparison. The capacity for the F-lipopeptides to spontaneously adsorb at the air/water interface and form monolayers when combined with dipalmitoylphosphatidylcholine (DPPC) was investigated. The F-lipopeptides 1–3 demonstrated a markedly enhanced tendency to form monolayers at the air/water

• ability to self-assemble into spontaneously adsorbed monolayers at the air/water interface and also to adsorb on a DPPC monolayer spread at the air/water interface. Finally, the size and stability characteristics of perfluorohexane (F-hexane)-stabilized microbubbles with DPPC/DPPE-PEG2000 shells and

• analysis, the products 1–4 had high purity (>99%) (Supporting Information File 1, Figures S1–S12). Behavior of lipid-peptide conjugates at the air/water interface Spontaneous adsorption of lipid–peptide conjugates at the air/water interface. In order to investigate the capacity for F-lipopeptides 1–3 to

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• -(methylsulfanyl)acrylate (42), thus questioning their natural source from Celeribacter. These results demonstrate that the six Celeribacter strains are able to degrade methionine and DMSP with formation of MeSH as a source for the likely non-enzymatic oxidation in the presence of air to 37 and 38, opening

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• -quinone 3a, which was previously reported by us [14]. The product 6a is air-stable at ambient conditions both in solid state and in solution. According to X-ray data, the 1,3-dithiole ring in the molecule is almost planar, its geometry is typical of 1,3-dithiole-2-thione species [26][27][28] (Figure S1 in

• similar observations were reported previously for monocyclic thiete compounds [35][36]. Benzothietes usually behave as highly reactive and labile species, however, solid samples of o-quinone 7 could be stored for months on air at ambient conditions without significant changes. Most probably, such

• tested only typical properties of the dioxolene function of the novel synthesized species. As mentioned above, all new o-quinones 6a–d and 7 are stable at rt on air both in crystalline form and in solution. Like other sterically hindered o-quinones, they can undergo two consecutive one-electron

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• : PDFA is available from the reaction of triphenylphosphine with halodifluoroacetate salts such as BrCF2CO2K. It exists as a free-flowing white solid that is not sensitive to air or moisture [33]. Upon heating to 80 °C in N-methylpyrrolidone, the compound decarboxylates and acts as a source of the ylide

• (trifluoromethyl)mercury (IHgCF3) and bis(trifluoromethyl)mercury (Hg(CF3)2) [57]. However, despite good synthetic conversions having been obtained with Seyferth's reagent [58] and the general insensitivity of organomercurials to air and moisture, the presence of mercury in all of these structures is a major

• -difluorocyclopropane derivative 53 plus cadmium fluoride [61][62]. However, cadmium compounds are highly toxic and furthermore (CF3)2Cd is pyrophoric in air and liable to explode upon warming to room temperature. Tris(trifluoromethyl)bismuth (54) is also a source of difluorocarbene, that is generated during the

Selective synthesis of α-organylthio esters and α-organylthio ketones from β-keto esters and sodium S-organyl sulfurothioates under basic conditions

• Jean C. Kazmierczak,
• Roberta Cargnelutti,
• Thiago Barcellos,
• Claudio C. Silveira and
• Ricardo F. Schumacher

Beilstein J. Org. Chem. 2021, 17, 234–244, doi:10.3762/bjoc.17.24

• 4 equivalents of a base were used, a series of differently substituted α-thio esters were obtained with up to 90% yield. On the other hand, employing 2 equivalents of a base, α-thio ketones were achieved after 18 h under air. Furthermore, after a shorter reaction time, the isolation of keto–enol

• methods. Thus, the main features of the current strategy include the use of Bunte salts, avoiding air-sensitive and foul-smelling starting materials [53][54] to react with β-keto esters under NaOH-mediation to selectively produce α-thio esters or α-thio ketones as target products. Additionally, no

• starting materials to establish the best reaction conditions under an air atmosphere (Table 1). In our preliminary experiment, a mixture of 1a (1.0 mmol) and 2a (0.5 mmol), using NaOH (2 equiv) as a base in toluene (3.0 mL), was stirred at 100 °C for 18 h. Under these reaction conditions, the products

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• intensities were recorded in dependence on the scattering angle. The absorption spectra were recorded on a SHIMADZU UV Spectrophotometer (UV-1800) with a slit width of 1.0 nm and a range of 200 nm ≤ λ ≤ 800 nm. The spectra were recorded against air as a reference. For all measurements 10 mm quartz cuvettes

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• ) and 25 (syn-HT) in an aqueous solution increased from 23 to 76% (60 min, under N2, O2, and air), with a high selectivity (>99%). However, for reactions without adding CB[8] as a catalyst, the conversion yield was below 10%. In addition, the fluorescence enhancement was also observed at a host/guest CB