Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• ) [94]. Interestingly, the protocol used air as the oxidant, avoiding the use of stoichiometric oxidants like previous radical cyclization cascades. Generally, substrates with an electron-withdrawing group afforded the product in greater yield. The reaction proceeds through the formation of a sulfonyl

• the reaction conditions has allowed for several different difunctionalization reactions of alkenes through the denitrogenative radical generation of carbazates. The subsequent radical has been shown to undergo coupling with oxygen sources like peroxides [114][115] and air [116]. In 2020, Qian and

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• , under air atmosphere for 10 min; yields are reported for the isolated products. Cases encountered by other p-QMs examinations. DBU-catalyzed 1,6-conjugate addition for the synthesis of isonitrile diarylmethanes 4a–h. Reaction conditions unless otherwise specified: 1 (0.2 mmol), 2 (0.4 mmol), DBU (0.06

• mmol), MeCN (1.0 mL), 80 °C, under air atmosphere for 10 h; yields are reported for the isolated products. Synthetic applications of the synthesized compound 3b. Mechanistic studies and proposed mechanism. Optimization of the reaction conditions for the sulfonylation and isonitrilation of p-quinone

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• strains were prepared according to the M27-A2 document. After adding 100 μL of working suspension in microtiter plate wells, 250–0.12 μg/mL final concentration ranges were obtained. Inoculated plates were incubated for 48 h in ambient air at 35 °C. The lowest concentration of a compound that inhibits

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

• Nicolai Wippert,
• Martin Nieger,
• Claudine Herlan,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

• [3,4-d][1,2,3]triazine compounds 5 (Scheme 4). The successful cyclizations gave the desired pyrazolo[3,4-d][1,2,3]triazines 5 in moderate to good yields. Not all cyclization products were air-stable. While compounds 5a–d with a benzylic side chain in R1'' were stable, a full characterization was

• possible, especially pyrazolotriazines with an aliphatic substituent on the pyrazole-nitrogen (5e–i) degraded rapidly in contact with air/moisture. The conversion of the regioisomeric compounds 10 to 6 failed under the conditions described in Scheme 4. The triazene protective group could not be cleaved

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• to moisture and air. Therefore, this method offers an attractive and robust option for the preparation of chiral β-silyl nitroalkanes. In sharp contrast to the aforesaid reaction, organocatalytic conjugate addition reactions of nitroalkanes to enones have been well studied [39][40][41][42][43]. To

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• spectroscopy experiments of drop casted films of the respective polymers were carried out. The respective polymers were heated to 150 °C and an IR spectrum was recorded every 20 K. Afterwards the polymers were air cooled and further spectra at 100, 70, and 25 °C were recorded. Figure 4 displays the aromatic C

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• ][42][43]. For the synthesis, 500 mg of red phosphorus, 20 mg of Sn and 10 mg of SnI4 were placed into a quartz ampoule with the dimensions of 20 cm length and 1.5 cm width. The air was evacuated by vacuum, and the ampoule was left to dry at least for 30 min under vacuum. The sealed ampoule was placed

• the NMR tube. The reaction tube was irradiated by using a Philips 150 W PAR38E E27 halogen pressure glass type bulb with strong IR-A (NIR) emission. The light intensity inside the reaction tube was ≈200 mW·cm−2. The light bulb was attached to the top of a photoreactor setup equipped with a large air

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• -1,3-enynes 34 and amines was carried out smoothly in THF at room temperature under air. The protocol showed broad substrate scope, and various different aromatic substrates (R1, R2, and R3 = aryl) reacted well. However, no target product was observed when aliphatic amine was used as substrate under

Isolation and characterization of new phenolic siderophores with antimicrobial properties from Pseudomonas sp. UIAU-6B

• Emmanuel T. Oluwabusola,
• Olusoji O. Adebisi,
• Fernando Reyes,
• Kojo S. Acquah,
• Mercedes De La Cruz,
• Larry L. Mweetwa,
• Joy E. Rajakulendran,
• Digby F. Warner,
• Deng Hai,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2021, 17, 2390–2398, doi:10.3762/bjoc.17.156

• river in North Central Nigeria (8.4799° N, 4.5418° W). The sediment samples were air-dried at room temperature for 48 h. Ten grams (dry weight equivalent) were suspended in 100 mL of sterile distilled water, vortexed at high speed, and 1 mL of diluent was serially diluted (10−2 and 10−4). Isolation of

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• oxidative conditions, catalyzed by CuTC to give the desired product 101 (Scheme 15a). On the other hand, Yang synthesized bis(indol-3-yl)sulfides 105 through the reaction of indole with elemental sulfur, catalyzed by iron(II) sulfate in the presence of stoichiometric amounts of KI in air [83]. The I− from

• mono- and di(phenylthio)-substituted indoles 139 and 140 (Scheme 18d) [97]. Catalytic iodine was used to oxidize PhSSPh (138) to PhSI (141), to which indole adds to give (phenylthio)indole 139 along with HI. HI reduces SeO2 to Se. Se interacts with two molecules of indole in the presence of air to give

An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)

• Jochen Löblein,
• Thomas Lorson,
• Miriam Komma,
• Tobias Kielholz,
• Maike Windbergs,
• Paul D. Dalton and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2021, 17, 2095–2101, doi:10.3762/bjoc.17.136

• mechanical properties, cytocompatibility, biodegradability, and good printing properties [8][14][15], it is a hydrophobic polymer and immersion into fluids can result in air bubble capture within the scaffold structure, biofouling and non-specific cell interactions [16]. Protein adsorption and denaturation

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