Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• side, typical reactors used for classical mechanochemical synthesis are made of non-transparent materials such as stainless steel (SS), zirconia, or polytetrafluoroethylene (PTFE), making the use of photons operationally difficult. In this Perspective, we gathered selected examples to showcase how

• investigated. When o-terphenyl (10.1) was milled (30 Hz, PTFE balls) and irradiated (λ = 270 nm) in the presence of silica gel (bulking agent), I2 (1 equiv) as an oxidant, and K2CO3 (1 equiv) as a base in the presence of toluene, the expected product 10.2 was obtained in 81% yield after isolation upon 181 h of

Mechanochemical difluoromethylations of ketones

• Jinbo Ke,
• Pit van Bonn and
• Carsten Bolm

Beilstein J. Org. Chem. 2024, 20, 2799–2805, doi:10.3762/bjoc.20.235

• , entry 1). The reaction was conducted in a PTFE milling equipment with two milling balls (diameter: 10 mm). Changing to a heavier milling ball (diameter: 15 mm) resulted in a yield of 67% of 3a (Table 1, entry 2). Stopping the reaction after 60 min gave product 3a in 72% yield (Table 1, entry 3). At a

• reaction conditions with difluorocarbene precursor 2, KFHF (4 equiv) as activator, and CsCl or KCl (4 equiv) as grinding auxiliaries in a PTFE milling jar for 90 min at 25 Hz (Scheme 3). To get an initial efficiency estimate, the crude reaction mixtures were first analyzed by quantitative 1H NMR

Homogeneous continuous flow nitration of O-methylisouronium sulfate and its optimization by kinetic modeling

• Jiapeng Guo,
• Weike Su and
• An Su

Beilstein J. Org. Chem. 2024, 20, 2408–2420, doi:10.3762/bjoc.20.205

• the efficient mixing of organic phases (cyclopentadiene, 1,2-dichloroethane, and MeBu3NCl) and aqueous phases (30% NaOH) and optimized it by the use of a simple homemade “PTFE Raschig ring static mixer” (RRSM). The RRSM is simple in structure, easy to fabricate, inexpensive for many flow reaction

• = 112 mL. Continuous flow microreactor system The continuous flow microreactor system is shown in Figure 1. Solutions A and B were stored in two glass vials (500 mL) with lids and were preheated by two high-pressure PTFE pumps (pump A, pump B, JJRZ-10004F, Hangzhou JingJin Technology Co., Ltd.) and

• reaction coil. All preheat tubes, mixers, and reaction coils were immersed in the same water bath to maintain a constant temperature. Finally, after controlling the residence time, the reaction was terminated by pumping excess pure ice water through a high-pressure PTFE pump (Pump C, JJRZ-10004F, Hangzhou

Diameter-selective extraction of single-walled carbon nanotubes by interlocking with Cu-tethered square nanobrackets

• Guoqing Cheng and
• Naoki Komatsu

Beilstein J. Org. Chem. 2024, 20, 1298–1307, doi:10.3762/bjoc.20.113

• obtained by centrifugation at 50400g for 16 h and subjected to UV−vis−NIR measurements (Figure 3a). After concentrating the extract obtained above, the residue (e-SWNTs) was suspended in dichloromethane by sonication and filtered through a PTFE membrane (pore size 0.1 μm). This washing process was repeated

• PTFE membrane. This process to remove host molecules was repeated three times, until no absorption bands from the host molecules were observed in the UV−vis spectra of washings. After the resulting p-SWNTs were washed with dichloromethane several times to thoroughly remove all the organic molecules

Light on the sustainable preparation of aryl-cored dibromides

• Fabrizio Roncaglia,
• Alberto Ughetti,
• Nicola Porcelli,
• Biagio Anderlini,
• Andrea Severini and
• Luca Rigamonti

Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95

• (35 wt % solution, d = 1.13 g/mL, 2.00 mL, 23.3 mmol, 4.7 equiv) was added over 2 h using a syringe pump, through a small PTFE tube inserted through the side arm of the Schlenk tube. After the addition was complete, the mixture was left under stirring for 1 h and 30 min. Once the mixture was

• , 2.33 equiv) in H2O2 (35 wt % aqueous solution, 4.8 mL, 56 mmol, 4.67 equiv) was added to the mixture over 15 min with a syringe pump, through a PTFE tube inserted in the top of the condenser. The system was then refluxed for 48 h. Once cooled to rt, the reaction mixture was neutralised with solid

• solution of NaBr (2.88 g, 28 mmol, 2.33 equiv) in H2O2 (35 wt % aqueous solution, 4.8 mL, 56 mmol, 4.67 equiv) was added over 15 min through a PTFE tube inserted at the top of the condenser, by means of a syringe pump. The flask was then heated to 50 °C for 48 h, cooled to rt, and unwrapped. Under stirring

Comparison of glycosyl donors: a supramer approach

• Anna V. Orlova,
• Nelly N. Malysheva,
• Maria V. Panova,
• Nikita M. Podvalnyy,
• Michael G. Medvedev and
• Leonid O. Kononov

Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18

• triturated with anhydrous benzene (5 mL), and the extract was filtered through a PTFE microfilter (0.45 μm, 13 mm diameter, Iso-Disk, Supelco). The filtrate was concentrated under reduced pressure and the residue was dried in vacuo to give 2 as a colorless solid (118.8 mg, 73%). [α]D19 −87.4 (c 4.3, CHCl3

Preparing a liquid crystalline dispersion of carbon nanotubes with high aspect ratio

• Keiko Kojima,
• Nodoka Kosugi,
• Hirokuni Jintoku,
• Kazufumi Kobashi and
• Toshiya Okazaki

Beilstein J. Org. Chem. 2024, 20, 52–58, doi:10.3762/bjoc.20.7

• 200 mL of water, the DWCNT-glycerol mixture was filtered through a 1.0 μm pore size polytetrafluoroethylene (PTFE) membrane (Merck, Omnipore 47mm). To ensure complete removal of glycerol from the DWCNTs, we repeated the washing process until 2 L of water had passed through the membrane, resulting in

A series of perylene diimide cathode interlayer materials for green solvent processing in conventional organic photovoltaics

• Kathryn M. Wolfe,
• Shahidul Alam,
• Eva German,
• Fahad N. Alduayji,
• Maryam Alqurashi,
• Frédéric Laquai and
• Gregory C. Welch

Beilstein J. Org. Chem. 2023, 19, 1620–1629, doi:10.3762/bjoc.19.119

• be concluded at this time. Solution processing All four compounds are soluble in ethyl acetate, and each was probed for its saturation point. This was done by adding each material to 1 mL of ethyl acetate until solids did not dissolve, where after this each solution was filtered with a 0.22 μm PTFE

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• . Emulsion polymerization is also a widely-used method in radical polymerization. It is applied to produce several commercially important polymers such as acrylic rubber, nitrile rubber, and polytetrafluoroethylene (PTFE). Polymerization happens in latex or colloid particles that are formed under the action

• generate alkyl radicals for surface modification [161]. Electrochemical surface modification also works for inert PTFE surfaces in the presence of a 2,2’-dipyridyl redox mediator [162]. Photons and high-energy charged particles can transfer their energy to bound electrons in atoms, exciting the electron to

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

• for 4 hours. Afterwards purification included dissolving the crude product in CH2Cl2, filtration over a PTFE syringe filter and concentrating the filtrate under reduced pressure. Employing strong bases such as KHMDS, NaOt-Bu or NaOH did not lead to the desired product (Table 1, entries 7–9). All three

• filtered over a PTFE syringe filter (0.45 μm). The filtrate was concentrated under reduced pressure. The product 5 was obtained as the CH2Cl2 adduct as a colourless solid (86 mg, 0.15 mmol, 91%). General synthetic routes to copper(I)/NHC complexes (X = Cl, Br). Preparation of sophisticated Cu(I)/NHC

Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone

• Solomiia Borova and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21

• K. HFIP was supplemented with 3 g/L potassium triflate, and the flow rate was adjusted to 0.50 mL/min. Calibration was performed using PEG standards with molar masses ranging from 0.1–1,000 kg/mol. Before every measurement, samples were filtered through 0.2 µm PTFE filters, Roth (Karlsruhe, Germany

Heterogeneous metallaphotoredox catalysis in a continuous-flow packed-bed reactor

• Wei-Hsin Hsu,
• Susanne Reischauer,
• Peter H. Seeberger,
• Bartholomäus Pieber and
• Dario Cambié

Beilstein J. Org. Chem. 2022, 18, 1123–1130, doi:10.3762/bjoc.18.115

• low flow rate (10 μL/min) [43][44]. An alternative approach to obtain a narrower RTD is the reduction of the reactor diameter, as this would decrease the axial dispersion [45]. Replacing the glass column (i.d. 6.6 mm) with a PTFE capillary with a smaller inner diameter (i.d. 5/32”, 3.9 mm) resulted in

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• accumulation using a divided flow electrochemical cell. Quantification of NHC in IL solution The flow cell used in this work was previously described [36]. It is based on two electrode plates separated by a spacer/gasket fabricated from an PTFE sheet with its center cut away to form the electrolyte flow

• electrochemical reactor. C/PVDF anode before (A) and after (B) the first experiment (Table 1, entry 1). Expanded view of the electrochemical cell components: (a) Aluminium end plates; (b) insulating PTFE foil, (c) copper plate for electrical contact; (d) carbon electrode; (e) PTFE gasket (reaction channel and

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• ]. Column chromatography was carried out on silica gel (300–400 mesh). Analytical thin-layer chromatography was performed on glass plates of silica gel GF-254 with detection by UV. Standard techniques for synthesis under inert atmosphere and Schlenk glassware equipped with an 8 mm PTFE vacuum stopcock, were

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• and, thus, a large interface between the phases. Subsequently, the biphasic system is directly separated, employing a PTFE membrane separator, to afford a solution of isoamyl acetate in n-heptane, while the aqueous layer containing the lipase could be recycled. At 60 °C with a residence time of 8.6

• formation of hydrazone 28. As one equivalent of water is formed in this condensation process, which is detrimental for the subsequent Shapiro reaction, water is continuously removed by in-line separation of the reaction mixture using a PTFE-membrane separator. The organic layer is then mixed with a solution

• safe two-step synthesis of 56 from cyclohexanone. In the first step, a solution of cyclohexanone in dodecane is mixed in a Q-piece with hydrogen peroxide, nitric acid, and formic acid and subsequently pumped at room temperature through a PTFE tube reactor with a residence time of 93 min. The resulting

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• ) [93]. Cyclohexanone (25) was mixed with conc. formic acid, and a mixture of H2O2 (30%)/HNO3 (65%) in a PTFE reactor at rt. This led to the formation of the cyclic triperoxide 91 in 48% (isolated) yield. Interestingly, the equilibrium favors the formation of the trimer 91 over the corresponding dimeric

High-speed C–H chlorination of ethylene carbonate using a new photoflow setup

• Takayoshi Kasakado,
• Takahide Fukuyama,
• Tomohiro Nakagawa,
• Shinji Taguchi and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2022, 18, 152–158, doi:10.3762/bjoc.18.16

• [14][15][16][17][18][19][20]. Vinylene carbonate also serves as a useful synthetic building block for Diels–Alder reactions [21][22][23][24][25] and polymerization [26][27][28][29][30]. Results and Discussion Using a PTFE tube and PTFE connectors, we connected the photoflow setup with a chlorine gas

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

• addition of 1 M HCl (20 µL), diluted with acetonitrile (100 µL), and filtered through a PTFE membrane filter (0.45 µm). The standard amino acids (ᴅ-Thr, ʟ-Thr, and ʟ-allo-Thr) were subjected to derivatization with ʟ-FDAA by using the same method previously described. For the HPLC analysis, mixtures of the

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

• authors screened several other 3D printed reactors evaluating materials (PTFE, PLA or Nylon), volumes (1 or 10 mL), and channel shape (circular, square, or rectangular). The process was then merged with a hydrogenation step using the H-Cube® apparatus (Pd/C, 30 °C, 15 bar) for the continuous preparation

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• silicates of the glassware surface. To clarify the role of a glass vessel in our case, several experiments were carried out in a pressure reactor equipped with a PTFE tube (Table 1, entries 3–5). Under previously optimized reaction conditions (100 °C, Table 1, entry 2), mannoside 3a was isolated in only 8

• to the previous report [63], in our case the reaction was not fully stopped by changing the reaction vessel from glass to PTFE tube. At this point, we can confirm the ability of SO2 to activate the glycosyl fluoride with a probable co-promoting assistance of a glass vessel. Next, in order to increase

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

• Thomas Di Nardo and
• Audrey Moores

Beilstein J. Org. Chem. 2019, 15, 1217–1225, doi:10.3762/bjoc.15.119

• mechanochemical amorphization of chitin. We measured the crystallinity index of chitin after milling it in a vibration mill in an apparatus made of copper, aluminum, brass, tungsten carbide, zirconia, stainless steel, polytetrafluoroethylene (PTFE), or poly(methyl methacrylate) (PMMA). These materials offer a

• lies outside of the milling chamber where sample can pass in and out for continuous monitoring [48]. This allows for varying milling media with the benefit of in situ measurements. For some processes like reactive aging with enzymes [22], polytetrafluoroethylene (PTFE) jars were preferred over

• stainless steel ones, since the latter caused the reactive mixture to adhere to the jars, which was not the case of the former. In another example, for the metal-free transfer hydrogenation of carbonyl compounds, PTFE was used instead of steel to eliminate the possibility of catalysis from the milling media

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• ]oxazine-2,4(1H)-dione (9b). A 500 mL single neck round-bottomed flask equipped with a football-shaped PTFE stirring bar (16 mm × 37 mm) was charged with 2-amino-5-bromobenzoic acid (10.0 g, 46.3 mmol, 1.0 equiv) followed by the addition of tetrahydrofuran (230 mL, 0.2 molar) and solid triphosgene (13.7 g

• precipitated out after about 30 minutes at 70 °C. The heterogeneous reaction mixture was aged for 12 hours then cooled to room temperature (25 °C). The slurry was poured into a 600 mL beaker equipped with overhead mechanical stirrer (PTFE 75 mm paddle) containing 250 mL of deionized water. With vigorous

• for quinoline synthesis Ethyl 6-bromo-4-hydroxy-2-methyl-3-carboxylate (10b). To a 250 mL single-necked round bottom flask equipped with football-shaped PTFE stir bar (16 mm × 37 mm) was added isatoic anhydride 9b (10.85 g, 44.8 mmol, 1.0 equiv), ethyl acetoacetate (11.3 mL, 89.7 mmol, 2.0 equiv

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

• Nicole C. Neyt and
• Darren L. Riley

Beilstein J. Org. Chem. 2018, 14, 1529–1536, doi:10.3762/bjoc.14.129

• %, respectively. Flow-based reduction of aldehydes and ketones In developing a flow protocol a Uniqsis FlowSyn Stainless Steel Flow reactor with a Multi X automated sampler was utilized. The reactor set-up (Figure 1) involved the use of two HPLC pumps, a 2 mL mixing chip connected in series to a 14 mL HT PTFE

• isopropanol/water/NaHCO3 [1 M] (1:1:2) in a 2 mL mixing chip at ambient temperature. Thereafter, the solution was superheated to 110 °C while being passed through a 14 mL HT PTFE coil affording near quantitative conversion (92% isolated yield) with a residence time of 64 minutes in the mixing chip and heated

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• vessel (and its shape); the mass of the ball(s); and the hardness of the colliding materials. In order of descending hardness, zirconia, stainless steel, copper and PTFE have all been used to effect mechanochemical transformation of nucleoside or nucleotide substrates. During a study of amide coupling

• under ball-milling conditions, Lamaty and co-workers showed that deterioration of vessels and balls by physical abrasion and/or chemical leaching gave products in which (depending upon the nature of the jar) iron, chromium, zirconia or PTFE were detected [20]. This has influenced the choice of vessel

• for nucleoside and nucleotide chemistry as, although considerably cheaper, leaching of iron from stainless steel vessels in the presence of sulfur-containing materials [21] has been found to inhibit the preparation of thionucleoside [22] or thionucleotide [23] analogues. Although grinding using PTFE

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• copper and zinc, which is much harder and mechanically more resistant than pure copper. We tested two approaches, one using a completely brass milling assembly (brass milling vessels and balls), while the other combined brass milling balls with polytetrafluoroethylene (PTFE, Teflon) vessels. Surprisingly

• operating at 30 Hz in PTFE reaction vessels using stainless steel or brass balls. Fourier-transform infrared attenuated total reflectance spectroscopy (FTIR–ATR) was performed using a Perkin-Elmer SpectrumTwo spectrometer, from 4400 cm−1 to 500 cm−1, with resolution 4 cm−1 (Supporting Information File 1