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

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

• : microreactor; microreactor scale-up; monolith reactors; packed bed reactor; photoreactor scale-up; Review Introduction In the traditional chemical industry, thermochemical activation routes are mostly preferred. Light can also activate some molecules, which leads to fast and selective reaction pathways

• and a monolith are shown in Figure 5a and Figure 5b, respectively. The performance of a capillary photomicroreactor packed with TiO2-coated glass beads were compared to a photomicroreactor having the walls coated with TiO2. The degradation of methylene blue was chosen as a model reaction. Complete

• energy efficiency was the highest [63]. As mentioned in the previous section, structures such as beads or monolith supports are frequently used to increase the mass transfer in photoreactors. Zhao et al. studied beads made of glass, zircon, or steel in a capillary-based photomicroreactor. Opaque packing

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

Energy down converting organic fluorophore functionalized mesoporous silica hybrids for monolith-coated light emitting diodes

• Markus Börgardts and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 768–778, doi:10.3762/bjoc.13.76

• principle, the implementation in a white light emitting monolith for down converting commercially available UV light emitting diodes. Results and Discussion A general approach to mesoporous organo–silica hybrid materials takes advantage of the condensation of triethoxysilyl-functionalized functional organic

• concept, we prepared four examples of white light emitting LEDs with organic phosphors. Therefore, UV-emitting LEDs were early immersed into the reaction mixture upon monolith formation. After aging, according to the described method, the UV emitting diodes were coated with the white light emitting hybrid

• the focus of further research. Further investigations are directed to the determination of quantum yields of the monolith-functionalized materials since their quantum yields could show higher efficiencies in comparison to the powder samples due to elimination of scattering of the excitation and

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

• surface and containing precious metal sites (washcoat) [98][99]. They are largely reported in the chemical engineering literature for gas-phase, unselective thermal processes [100][101]. A monolith is “a shaped, fabricated intractable article with a homogeneous microstructure that does not exhibit any

• ][108], which addresses the need of both efficient processing (within small pores) and effective mass transport (by macropores) [109][110]. This kind of monolith obtained by spinodal decomposition joins the advantages of high surface area typical of mesoporous material, spanning from 200 to 1200 m2 g−1

• viscosity; v linear velocity), thanks to the high permeability coefficient k > 0.25 μm2, which is proportional to the macroporous size D2 [113]. The catalytic performance of these monoliths has been compared in continuous flow as a single piece or packed-bed (ground monolith 60–120 μm) and in batch

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• of remotely functionalised ligands within the metal coordination sphere. A very efficient covalent immobilisation through anionic ligands was reported by Buchmeiser et al., who synthesised a series of monolith-supported catalysts (such as 1) which gave metathesis products with extremely low residual

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

• a selective heating element [21], or in a Pd-supported silica monolith flow reactor by Haswell et al. [22], using palladated Raschig rings in a PEEK [poly(ether ether ketone)] reactor by Kirschning et al. [23], in a de novo glass coiled flow cell by researchers at Boehringer Ingelheim [24] and with

The application of a monolithic triphenylphosphine reagent for conducting Ramirez gem-dibromoolefination reactions in flow

• Kimberley A. Roper,
• Malcolm B. Berry and
• Steven V. Ley

Beilstein J. Org. Chem. 2013, 9, 1781–1790, doi:10.3762/bjoc.9.207

• possible to perform the Appel reaction using the same monolith and the relationship between the mechanisms of the two reactions is discussed. Keywords: bromination; flow chemistry; Ramirez gem-dibromoolefination reaction; solid-supported reagent; triphenylphosphine monolith; Introduction The advantages

• continuous-flow chemistry systems. Monoliths are a single continuous piece of uniformly porous material, prepared by precipitation polymerisation of a functionalised monomer [16][17][18][19][20]. The monolith internal structure varies compared to bead-like supports, consisting of a combination of large

• monolith to the Appel reaction (the transformation of alkyl alcohols to the corresponding bromides), we wished to investigate the application of this monolith to the closely related Ramirez gem-dibromoolefination reaction; the formation of gem-dibromoolefins from aldehydes or ketones. In 1962 Ramirez

The application of a monolithic triphenylphosphine reagent for conducting Appel reactions in flow microreactors

• Kimberley A. Roper,
• Heiko Lange,
• Anastasios Polyzos,
• Malcolm B. Berry,
• Ian R. Baxendale and
• Steven V. Ley

Beilstein J. Org. Chem. 2011, 7, 1648–1655, doi:10.3762/bjoc.7.194

• purification. Keywords: Appel reaction; bromination; flow chemistry; solid-supported reagent; triphenylphosphine monolith; Introduction Flow chemistry is well-established as a useful addition to the toolbox of the modern research chemist, with advantages accrued through increased efficiency, reproducibility

• application of this monolith to the transformation of an alkyl alcohol into the corresponding alkyl bromide by using carbon tetrabromide in the Appel reaction. In the 1960s Ramirez and co-workers reported the formation of a phosphine–methylene species when triphenylphosphine was mixed with carbon tetrabromide

• both the solution or solid-phase reactions (5% with solution-based triphenylphosphine and 18–29% with solid-supported triphenylphosphine), indicating that path B is the major pathway in either case [40][43]. Using a polystyrene-based triphenylphosphine monolith we hoped to benefit from the accelerated

Scaling up of continuous-flow, microwave-assisted, organic reactions by varying the size of Pd-functionalized catalytic monoliths

• Ping He,
• Stephen J. Haswell,
• Paul D. I. Fletcher,
• Stephen M. Kelly and
• Andrew Mansfield

Beilstein J. Org. Chem. 2011, 7, 1150–1157, doi:10.3762/bjoc.7.133

• been developed to perform Suzuki–Miyaura reactions under a microwave heating regime, in which the volumetric throughput of a Pd-supported silica monolith can be used to increase the quantity of the product without changing the optimal operating conditions. Two silica monoliths (both 3 cm long), with

• reactor. The Pd-supported silica monolith flow reactor was then placed into the microwave cavity and connected to an HPLC pump and a backpressure regulator to minimize the formation of gas bubbles. The flow rate and microwave power were varied to optimize the reactant contact time and temperature

• , respectively. Under optimal reaction conditions the quantity of product could be increased from 31 mg per hour to 340 mg per hour simply by changing the volumetric capacity of the monolith. Keywords: continuous flow; microwave heating; monolith; scaling-up; Suzuki–Miyaura reaction; Introduction Interest in

ROMP-Derived cyclooctene-based monolithic polymeric materials reinforced with inorganic nanoparticles for applications in tissue engineering

• Franziska Weichelt,
• Solvig Lenz,
• Stefanie Tiede,
• Ingrid Reinhardt,
• Bernhard Frerich and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, 1199–1205, doi:10.3762/bjoc.6.137

• decreases. A decrease of the compressibility, i.e., an increase in the compressive force-compression (CF-C) ratio of 56% was observed for reinforcement with the addition of 12 wt % CaCO3 (1.08 MPa for reinforced monolith vs 0.62 MPa for unmodified monolith). Thus, CaCO3-reinforced monoliths were more

• monolithic materials were cut into discs ~1–2 mm in height and ~10 mm in diameter and subsequently sterilized via γ-irradiation. Thereafter, these monolith scaffolds were seeded with human adipose tissue-derived stromal cells (hATSCs). Proliferation of the cells was monitored up to the 16th day (Figure 2

• hydroxide (Ca5(PO4)3OH) as evidenced by XRD measurements (a), SEM picture of the nanoparticles (b), structures of COE-derived monoliths containing 12 wt % CaCO3 (c) and 12 wt % HAp (d), and EDX-measurements of a monolith containing 12 wt % CaCO3 (Ca-mapping) (e). (a) Cell growth of human adipose tissue

Polyionic polymers – heterogeneous media for metal nanoparticles as catalyst in Suzuki–Miyaura and Heck–Mizoroki reactions under flow conditions

• Klaas Mennecke and
• Andreas Kirschning

Beilstein J. Org. Chem. 2009, 5, No. 21, doi:10.3762/bjoc.5.21

• ; microreactor; monolith; palladium; Suzuki–Miyaura reaction; Introduction Functionalized solid supports like polymers loaded with homogeneous catalysts are well established in organic synthesis [1][2][3][4]. Simple purification of the products and easy recyclability of the catalysts are major advantages of

• , vinylbenzyl chloride and divinylbenzene as monomers and consists of very small bead-like particles (0.2–2 µm) which are connected through polymeric bridges. As a result an extended monolithic polymeric phase inside a glass monolith is created. Incorporation of the resin inside a porous glass has the advantage

• that the resin can only swell inside the glass while the glass monolith provides a stable rod-like shape inside the microreactor. The Merrifield-type resin was aminated to yield polyionic support 1. This polymer serves as an anchor to leave the metal species (sodium tetrachloropalladate; Na2PdCl4) in

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• drops during flow-through that can often be problematic with gel-type resins. The flexibility and ease for adjusting porosity, composition and shape of these materials is an additional advantage [37][38]. The monolith-supported chiral amino alcohol catalyst 29 has been developed for the enantioselective

• conversion of benzaldehyde to the desired (R)-alcohol 30 with 85:15 selectivity and 99% ee (Scheme 9). Lower enantioselectivities were observed in batch reactions using a homogeneous analogue (87% ee) and also for a heterogeneous analogue with the catalyst grafted onto Merrifield resin (89% ee). The monolith

• co-workers have designed a continuous-flow reactor system, PASSflow [40], based on the use of a functionalizable monolithic rod derived from a glass/polymer composite. This device was used for the dynamic kinetic resolution of epibromohydrin 32, using a monolith reactor functionalized with a chiral