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

• turnover determining step is likely not of photochemical nature. Based on this consideration, we turned to the reactor temperature as a means for process intensification. As expected, performing the reaction at a lower temperature proved detrimental (Table 1, entry 5). However, at higher temperatures, 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

• significant impact on the use and ultimately the successful adoption of flow chemistry into many research laboratories. Another inherent benefit of flow is the option of safely using solvents at temperatures significantly above of their standard boiling points, increasingly important for process

• intensification. The implicit high pressure self-contained environment created by a pumped flow system allows for superior reaction kinetics often achieved by elevating the working temperature of the system. This capability also opens up the opportunity for the integration of volatile and gaseous reagents into

Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives

• Emese Gal,
• Luiza Gaina,
• Hermina Petkes,
• Alexandra Pop,
• Castelia Cristea,
• Gabriel Barta,
• Dan Cristian Vodnar and
• Luminiţa Silaghi-Dumitrescu

Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242

• angle of 64.5°. The intermolecular distances are situated in the range 2.3–2.6 Å disclosing the lack of intermolecular interactions in the crystal structure. Scanning electron microscopy (SEM) analysis Besides process intensification leading to a shorter reaction time, another advantage of the

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

• selective, which would potentially reduce the downstream costs significantly if the process is optimized properly. With the transition towards green chemistry, the traditional batch photoreactor operation is becoming abundant in this field. Process intensification efforts led to micro- and mesostructured

• designing multiphase photoreactors, and this complicates the design even further [10]. Photoreactions are typically performed in batch reactors. With the process intensification efforts towards green chemistry approaches, continuous flow technologies, micro- and mesostructured flow photoreactors having

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

Biocatalytic synthesis of the Green Note trans-2-hexenal in a continuous-flow microreactor

• Morten M. C. H. van Schie,
• Tiago Pedroso de Almeida,
• Gabriele Laudadio,
• Florian Tieves,
• Elena Fernández-Fueyo,
• Timothy Noël,
• Isabel W. C. E. Arends and
• Frank Hollmann

Beilstein J. Org. Chem. 2018, 14, 697–703, doi:10.3762/bjoc.14.58

• biocatalytic processes have been reported in flow reactors [19], mostly advocating easier process intensification in combination with enzyme immobilization [20][21][22][23]. Also the higher oxygen-transfer rates in flow reactions compared to batch reactions have been emphasised by several groups. Here, reactor

High-yielding continuous-flow synthesis of antimalarial drug hydroxychloroquine

• Eric Yu,
• Hari P. R. Mangunuru,
• Nakul S. Telang,
• Caleb J. Kong,
• Jenson Verghese,
• Stanley E. Gilliland III,
• Saeed Ahmad,
• Raymond N. Dominey and
• B. Frank Gupton

Beilstein J. Org. Chem. 2018, 14, 583–592, doi:10.3762/bjoc.14.45

• chemistry; hydrogenation; hydroiodic acid; hydroxychloroquine; Introduction Our research group has been focused on the development of new synthetic methods for the preparation of a variety of active pharmaceutical ingredients for global health applications by employing the principles of process

• intensification [1][2][3]. In 2016, estimated 212 million cases of malaria, including 429,000 fatalities, were reported worldwide, with the majority of these cases occurring in sub-Saharan Africa and Southern Asia [4]. The malaria epidemic is particularly difficult to control due to the multidrug resistant nature

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

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

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• hydrogenation reaction of alkynes is thus of utmost importance [14][15]. Compared to batch setups, considerable process intensification [16][17] to this regard can be provided by continuous-flow operations either in terms of safety, purification, waste emission, durability, reproducibility, automation, energy

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• examples, α-hydroxy ketones (benzoin reaction) and 1,4-diketones (Stetter reaction) [1][2][3][4]. The synthetic utility of the umpolung methodology has therefore spurred intensive research on process intensification through the heterogeneization of NHC catalysts [5][6][7][8][9] for facilitating the post

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• . Besides batch reactors, in the last decade these techniques have been adapted to flow systems, which provide greater efficiency, flexibility and lower energy consumption, or in high-throughput applications. Our experience in process intensification and innovative reactors took advantage from flow

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• activity is often low, creating a demand for process intensification. In the last decade, different methods of process intensification have been proposed and tested for both fine-chemical and bulk-chemical processing [7][8][9]. It makes sense to test process intensification for biochemical processing as

• well. Microreactors, as a preferred process intensification tool, have gained considerable importance due to their many advantages over conventional batch reactors, including rapid heat and mass transfer, high surface area-to-volume ratios for dispersed media, and short processing times [10]. Indeed

One-step synthesis of pyridines and dihydropyridines in a continuous flow microwave reactor

• Mark C. Bagley,
• Vincenzo Fusillo,
• Robert L. Jenkins,
• M. Caterina Lubinu and
• Christopher Mason

Beilstein J. Org. Chem. 2013, 9, 1957–1968, doi:10.3762/bjoc.9.232

• advantages for scale up, certainly in terms of process intensification or in combination with reagent and scavenger cartridges for multi-step synthesis [11], and is possible using conventionally heated micro- or mesofluidic flow devices [12][13], but is also feasible under microwave dielectric heating

• by Kappe, Kunz and Kirschning revealed that continuous flow processing gave better conversions and improved catalyst recycling, with no loss of activity [26]. A range of other applications have been explored, from a continuous flow isothermal narrow channel microreactor for process intensification of

The Eschenmoser coupling reaction under continuous-flow conditions

• Sukhdeep Singh,
• J. Michael Köhler,
• Andreas Schober and
• G. Alexander Groß

Beilstein J. Org. Chem. 2011, 7, 1164–1172, doi:10.3762/bjoc.7.135

• blocks and secondary thiolactame and thioamide derivatives. To improve the long reaction times we investigated the Eschenmoser coupling under process intensification conditions. Therefore, reaction temperatures far beyond the solvent boiling point were applied under pressurized flow conditions for a

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• order to conduct highly exothermic reactions safely [1][2][3][4][5][6][7][8][9]. More recently, following the concepts of “Process Intensification” and “Novel Process Windows” [10][11][12], flow chemistry executed in high-temperature and/or high-pressure regimes have become increasingly popular [13

• explanations for these highly unusual rate accelerations are presented. In addition, general aspects of reactor degradation, corrosion and contamination effects of importance to continuous flow chemistry are discussed. Keywords: flow chemistry; heterogeneous catalysis; microreactors; palladium; process

• intensification; Introduction Microreactor technology has opened up new avenues for synthetic organic chemistry [1][2][3][4][5][6] and the chemical manufacturing industry [7][8]. Traditionally, most synthetic transformations performed in microreactors have involved ambient or even low-temperature conditions in