Preparation of mono-substituted malonic acid half oxyesters (SMAHOs)

• Tania Xavier,
• Sylvie Condon,
• Christophe Pichon,
• Erwan Le Gall and
• Marc Presset

Beilstein J. Org. Chem. 2021, 17, 2085–2094, doi:10.3762/bjoc.17.135

• reagents. In our hands, these reagents appear to be stable to air or moisture and have been stored for several months at 4 °C. The alkylation/hydrolysis of malonates afforded a straightforward access to such derivatives but the use of an alcoholic base in the saponification step precludes the presence of

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• turned on. This can be explained by a low oxygen inhibition, which is an advantage for different applications where the photopolymerization under air is required. As shown in Figure 2 and Figure 3, only CNa, CBPh3, CI3, and CI10 show a long inhibition time, and this can be ascribed to the low absorption

• (10) CI10. Photopolymerization profiles of PETIA monomer under air (acrylate functions conversion vs irradiation time) in the presence of a NIR dye/iod/NPG 0.1:3:2. %w/w/w system. A) NIR dyes with BPh4− and Na+ as counter anion and counter cation: (1) Ca, (2) Cb, (3) CBPh1, (4) CBPh4, (5) CNa, and (6

• ) IR 813. B) NIR dyes with I− as counter anion: (1) CI3, (2) CI4, (3) CI5, (4) CI8, (5) CI9, and (6) IR 813; upon exposure to a 785 nm laser diode (0.9 W/cm2), thickness = 1.4 mm. The irradiation starts at t = 10 s. Photopolymerization profiles of PETIA monomer under air (acrylate functions conversion

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• monofunctionalized naphthyl substrates. These authors demonstrated that the rhodium-catalyzed oxidative 1:2 coupling reactions of arylboronic acids 7 with alkyne 8 occurred in the presence of a copper–air oxidant, to give the corresponding 1,2,3,4-tetrasubtituted anthracene derivatives 9a and 9b (Scheme 1) [34

• , the authors added previously prepared triarylmethanes 52 to the reaction mixture under air atmosphere, and then under oxygen atmosphere. Therefore, an efficient Bi(OTf)3/O2 system promoted the oxidation/aromatization step, providing the 9,10-disubstituted 2,3,6,7-tetraalkoxyanthracenes 53 in good

• DIBAL-H reduction, and later to aldehydes 199 by Dess–Martin periodinane (DMP) oxidation. The aldehydes 199 were treated with BINOL-PO2H in chloroform, in the presence of air and light, to produce the corresponding anthraquinones 200 in excellent yields (93–99%) [82]. In this review, a more detailed

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• detected, but N-fluoroimides 2-1 and 2-2 were formed. The stability of these N-F compounds was low, since they decomposed to H2NCO(CF2)nCOOH upon standing with air. 1-3. 1-Fluoro-2-pyridone In 1983, Purrington and co-worker synthesized 1-fluoro-2-pyridone (3-1) as a fluorination agent [24]. When 2

• examples with 6-1 are shown in Scheme 16. This reagent proved to be very hygroscopic and deteriorated in air. In terms of fluorination yields, N-fluoroquinuclidinium fluoride (6-1) was however superior to Purrington’s 1-fluoro-2-pyridone (3-1) [24][25], but inferior to Barnette’s N-fluoro-N

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• the tertiary position using the manganese–salen catalyst. Furthermore, this Mn-catalyzed azidation protocol is highly robust in air, highlighting the practical simplicity of late-stage C–H azidation of bioactive molecules. A plausible reaction pathway was proposed, as illustrated in Figure 3. Similar

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• , Universitätstraße 31, D-93053 Regensburg, Germany 10.3762/bjoc.17.121 Abstract We have developed a cerium-photocatalyzed aerobic oxidation of primary and secondary benzylic alcohols to aldehydes and ketones using inexpensive CeCl3·7H2O as photocatalyst and air oxygen as the terminal oxidant. Keywords: alcohol

• air as the oxidant (Table 1). The best results were found using 10 mol % CeCl3·7H2O as a photocatalyst and 10 mol % of NaHCO3 as a base in CH3CN under blue LED irradiation at 50 °C for 35 h giving compound 2a in 65% isolated yield (Table 1, entry 1). The product formation was reduced upon employing

• yield of 35% (Table 1, entry 12). Employing an external oxidant such as (NH4)2S2O8 instead of air diminished the yield (Table 1, entry 13). The substitution of air with a balloon of oxygen afforded 2a in 25% yield (Table 1, entry 14), while employing an argon atmosphere led to only trace amounts of the

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• mixture was dissolved in dichloromethane and precipitated from diethyl ether resulting in about 50% polymer yield featuring Mn values of 1500–1800 g/mol [30]. Next, the oxidation stability of the catalysts was tested. For this purpose, the three different phosphines were exposed to air for 14 d in dark

• radical cations of the phosphines under investigation were calculated by density functional theory (DFT), namely B3LYP-def2-TZVPPD. According to criterion introduced by Stewart et al. postulating air stability of phosphines when the SOMO energy is higher than −10 eV, the three derivatives should be air

• of TPP becomes competitive to the one of the more expensive TMTPP. Furthermore, TMTPP is somewhat more sensitive to oxidation in air than TPP. Nevertheless, exclusion of air is, in contrast to trialkylphosphines, not mandatory. Oxidation under typical reaction conditions (reaction time not longer

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