CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• formation of allylic carbenium ions, such as 103 [81]. α-(Trifluoromethyl)alkynylcarbenium ions It has been reported that the complex of Co2(CO)6 and propargyl alcohols allows the facile generation of the corresponding propargylium ions (Nicholas reaction) in a relatively strong acidic medium (i.e., TFA

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

• place in β-keto esters, which is followed by CO2 displacement under heating [61][62][63][64]. We assume that in our case, when only 2 equiv of base are used, the keto–enol tautomer intermediates undergo a hydrolysis–decarboxylation process preferentially to a retro-Claisen reaction. This process forms

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

• activity (618.3 mmol⋅g−1⋅h−1) and an excellent stability (with a turnover number (TON) of 6417 after 75 h). Moreover, when the electron donor 1,3-dimethyl-2-phenyl-1,3-dihydrobenzimidazole (BIH) was added, the hybrid material functioned as an efficient photocatalyst for the reduction of CO2 to CO with 0.26

• (c) EY. Republished with permission of The Royal Society of Chemistry from [30] (“Host–guest chemistry between cyclodextrin and a hydrogen evolution catalyst cobaloxime” by M. Kato et al., New J. Chem. vol. 43, © 2019); permission conveyed through Copyright Clearing Center, Inc. Conversion of CO2 to

The fluorescence of a mercury probe based on osthol

• Guangyan Luo,
• Zhishu Zeng,
• Lin Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 22–27, doi:10.3762/bjoc.17.3

• performance of fluorescent probes. As shown in Figure 1A, the selectivity of OST to common metal ions is monitored by the fluorescence spectrum (λex = 325 nm). OST exhibits a weak fluorescence intensity at λex = 406 nm. When adding different metal ions (Hg2+, Ca2+, Na+, Mg2+, Al3+, Cd2+, Cu2+, Pb2+, Ni2+, Co2

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• ][7]. On the other hand, SF6 is a greenhouse gas [8]. It has indeed a global warming potential (GWP) 22,000 times greater than CO2 [9]. From an industrial point of view, this requires efficient methods of recycling or destroying SF6. This last point implies, because of its great stability, the use of

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

• has already been proven to be successful [4]. These examples show that photochemistry is a viable alternative to conventional chemistry approaches. In addition to specialty chemicals and wastewater treatment, photochemical pathways can also be used for methanol production [5], N2 fixation [6], and CO2

• photoreactor. The main reasons for this increase was the high surface-area-to-volume ratio and better illumination of the monolithic photoreactor [56]. The monolithic photoreactor was shown to have a higher yield for the CO2 photoreduction compared to a cell-type reactor that had no channels. This was

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• ). The cells were maintained at 37 °C, with 5% CO2 in a humidified chamber. Cell viability MTT assay Cell mitochondrial activity was tested using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which is based on the mitochondrial conversion of the tetrazolium salt into a

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• thermoelectric properties in addition to the onigiri-type core-shell assemblies have been reported for sumanene and its derivatives. More interestingly, its application in the absorption of small molecules such as NH3, CO2, CO, and H2 using density functional theory (DFT) calculations has also been revealed [25

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• of sugars [6], enzyme mimics [7], and the utilization of intermolecular cooperative effects [8] are further applications of photoswitchable catalysis. Particularly interesting and close to our approach is an early work by Inoue et al. who achieved control of the transformation of CO2 and 1,2

Three new O-isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus Vibrio

• Dandan Li,
• Enjuro Harunari,
• Tao Zhou,
• Naoya Oku and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1869–1874, doi:10.3762/bjoc.16.154

• culture for 12 h at 37 °C in an atmosphere of 95% air and 5% CO2 saturated with H2O, the drug solutions were transferred into each cell culture to make up 200 μL of the culture. The highest concentration of the vehicle solvents (MeOH or DMSO) was set at 0.5 vol %, where the growth of the cells was not

Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines

• Vladimir Kubyshkin

Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151

• this weakens their interaction. Similar considerations can be applied to the acidity of the carboxylic group (Figure 6B), where the mutual orientation of the C–X dipole and the carboxylate -CO2− charge has an effect [74]. In diastereomeric fluoroprolines there is a large difference in the mutual

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• oxazolidinones and five-membered cyclic carbonates of various structures. The most well-known strategies for the synthesis of oxazolidinones are the reaction of an amino alcohol with phosgene [5][22], the carbonylation reaction of β-amino alcohols with CO2 or dialkyl carbonates [23][24][25][26][27], the

• multicomponent reaction of rare-earth metal amides [28], the reaction of CO2 with propargylamines or aziridines [29][30] and the cycloaddition reaction of epoxides with isocyanates [31][32]. On the other hand, for the synthesis of five-membered cyclic carbonates, the cycloaddition of CO2 to epoxides, the

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• , mild oxidizing additives such as amine oxides, aminophosphines, phosphine oxides, and sulfoxides may be used as promoters to facilitate the dissociation step, by oxidatively removing one of the CO ligands in form of CO2 [40]. The most common oxidants are N-morpholine N-oxide (NMO), trimethylamine N

• -workers [46]. In this study, a wide variety of 1,6-enynes bearing fluorine atoms or fluorine-containing groups at the alkenyl or alkynyl positions were synthesized and evaluated as substrates in the intramolecular PKR with dicobalt octacarbonyl [Co2(CO)8] in CH2Cl2 and promoted by NMO. In general, the

• to high yields, except for those bearing marked electron withdrawing groups (Scheme 7). In 2005, Billard and co-workers reported the PKR of α-trifluoromethylated homoallylamine derivatives (Scheme 8) [47]. Both 1,7-enynes 18a and 18b (n = 1) underwent PKR in the presence of 1 equiv of Co2(CO)8 and 10

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• synthetically controlled to improve the photocatalytic CO2 reduction performance by Zhang and co-workers using plasma treatment [87]. The general process of photocatalysis in metal oxide semiconductors is illustrated in Figure 4 and is as follows: the photoexcitation of an electron across the band gap generates

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• methods from coal precursors. Yang et al. synthesized nitrogen-doped activated carbon from petroleum coke for an enhanced CO2 capture [7]. Pietrzak et al. used high volatile bituminous coals, brown coals and anthracites for modified activated carbon preparation [5][10][11][12]. Lillo-Ródenas et al

• solutions Xu et al. used energy-rich carbon precursors for the spherical carbon preparation via ultrasonic spray pyrolysis. Lithium, sodium or potassium propiolates are one class of such energy rich materials and exhibit leaving groups such as CO, CO2 or C2H2 eliminated by decarbonylation or decarboxylation

• . After preparation of char by carbonization of the precursor materials for a certain time at a defined temperature under inert gas atmosphere, steam, air or CO2 activate the materials at higher temperatures (800–1000 °C) to form a porous structure according to the Equations 1–3 [81][85][86]. It is

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• difficult to be directly activated by the excited state photocatalyst. For these reasons, the photocatalyzed decarboxylation often proceeds on the corresponding carboxylates, which are easier to be oxidized. This photoinduced SET, followed by the loss of CO2 as the sole byproduct, gives access to the

• reducible moiety, such as a redox-active ester (RAE). These species can accept one electron from the photocatalyst, and the ensuing reduced species releases the corresponding C(sp3) radical after a fragmentation and CO2 loss. This approach represents an alternative to oxidative decarboxylations, allowing

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• also can be applied to the reduction of carbon dioxide (CO2). Many photocatalytic materials containing porphyrins have been developed for CO2 reactions in organic synthesis, including photoinduced transformations [52][53][54][55]. Nagaraja and co-workers reported the first porphyrin-based MOF for

• different epoxides, whose conversion was proportional to the substrate size, using MOF1 and tetra-n-butylammonium bromide (TBAB) as photocatalyst and co-catalyst, respectively (Scheme 25). A successful gram-scale protocol was developed opening up perspectives for using these materials in CO2 reuse

• . This work is crucial for the success of the subsequent industrial process introduced by the pharmaceutical company Sanofi [80]. After this seminal publication, a consortium between Sanofi and UK/China universities also reported a green protocol for artemisinin synthesis using supercritical CO2 as a

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• , within the series of representative alkali and earth alkali ions (Li+, Na+, K+, Mg2+, Ca2+) and transition metal cations (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Hg2+, Pb2+), only the addition of Cu2+ caused a significant coloration of the initially colorless solution of 3a (c = 20 µM) in MeCN (Figure 1

• . Absorption (A) and fluorescence spectrum (B) of 3a in MeCN (c = 5 µM) in the absence (black) and in the presence of metal ions ca. 1 h after the addition. Red: Cu2+ (c = 15 µM), orange: Hg2+ (c = 100 µM), blue: Li+, Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Ag+, and Pb2+ (c = 100 µM each); λex = 470

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• give excellent chemical yields with good enantioselectivities for products 57–59 (Scheme 14). Interestingly, this approach could be extended to the synthesis of amino acids using cesium fluoride in the presence of CO2 gas to afford 60 and 61. From the representative examples shown below, it appears

• developed by Suginome [125], or B2pin2, along with various N-hydroxylamine derivatives (400) under ligand-influenced Cu catalysis, high regioselectivities were typically obtained [126]. A year later, Popp et al. reported a Cu-catalyzed regiospecific boracarboxylation of vinyl arenes using 1 atm CO2 and

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• TMSN3 as the azide source [10] (Scheme 1a). Coates described a Co2(CO)8-catalyzed ring-opening hydroformylation of oxazolines for the synthesis of β-amidoaldehydes [11] (Scheme 1a). However, the ring-opening N-alkylation of 2-oxazolines to produce 2-aminoethyl acetate derivatives under basic conditions

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• reaction conditions. The authors suggested first the photoexcitation of a [Cu(I)] species. Then, the excited [Cu(I)]* species reduces the NHP ester to form a carboxyl radical and the phthalimide anion, which binds to the [Cu(II)] species. After the elimination of CO2, the recombination of the alkyl radical

Two antibacterial and PPARα/γ-agonistic unsaturated keto fatty acids from a coral-associated actinomycete of the genus Micrococcus

• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku,
• Nobuyasu Matsuura,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 297–304, doi:10.3762/bjoc.16.29

• the cells at a final density of 5 × 103 cells/well, and 200 µL cultures thus made were incubated for 96 h at 37 °C in an atmosphere of 5% CO2 in air with 100% humidity. The viability of the cells was visualized by the addition of 50 μL of the medium containing XTT (1 mg/mL) and PMS (40 µg/mL) to each

• , and the plates were cultured for an additional 24 h at 37 °C in a 5% CO2 incubator. The luciferase activity and secreted alkaline phosphatase SEAP activity were measured in each well by using a Steady-Glo® luciferase assay (Promega, Madison, WI, USA) and Great ESCAPe SEAP Reporter System3 (Clontech

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• slightly lower yield. Attempts to carry out the Pauson–Khand reaction directly on the amino group before the acylation step did not work, nor using a modified approach using ammonium chloride and 1.5 equivalents of Co2(CO)8 under an inert atmosphere, as reported for similar reactions in the presence of

• Pauson–Khand (C) reaction. In a dry round bottom flask under a nitrogen flow Co2(CO)8 (0.1 equiv), N,N,N’,N’-tetramethylthiourea (0.6 equiv) and a solution of the enyne compound (1 equiv) were successively added in dry toluene (20 mL/mmol). Then, the reaction mixture was kept under a CO atmosphere and

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• of alkynyl nucleosides 2 and 3 were confirmed by 1H and 13C NMR spectroscopy and high-resolution mass spectrometry [64][65]. The conversion of alkynyl nucleosides 2 and 3 into the corresponding dicobalt hexacarbonyl nucleosides complexes of 4 and 5 was accomplished at room temperature (Co2(CO)8, THF

• reappearance upfield in the reaction products (i.e., 3.17 ppm in 6a and 4.27 ppm in 6b). In the 13C NMR spectra, the slightly broadened resonance of the metal carbonyl carbons at 199–200 ppm (199.4 ppm in both 6a and 6b) were characteristic of the product alkyne–Co2(CO)6 complexes. In the IR spectra, the

• the synthesis of hexacarbonyl dicobalt 5-alkynyluridines (4 or 5): A round-bottom flask was charged under a nitrogen atmosphere with Co2(CO)8 (0.222 g, 0.650 mmol), alkynyl nucleoside 2 or 3 (0.500 mmol), and THF (10 mL). The mixture was stirred at room temperature (22 °C) for 1 h. The solvent was

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• into Class 2, of which applications should be strictly limited, particularly in pharmaceutical industry. To develop an environmentally benign alternative of this useful method, the reaction has been extended to green solvents such as water [16], fluorous solvents [17], supercritical CO2 [18], and very