Mechanochemical synthesis of unsymmetrical salens for the preparation of Co–salen complexes and their evaluation as catalysts for the synthesis of α-aryloxy alcohols via asymmetric phenolic kinetic resolution of terminal epoxides

• Shengli Zuo,
• Shuxiang Zheng,
• Jianjun Liu and
• Ang Zuo

Beilstein J. Org. Chem. 2022, 18, 1416–1423, doi:10.3762/bjoc.18.147

• ]. Since their discovery, researchers have investigated several Co–salen complexes for the KR of epoxides with phenols as nucleophiles (Figure 1) [18][19]. Kim et al. described a catalytic system of a chiral Co–salen immobilized on meso/macroporous silica monoliths for the ring opening of epoxides [20

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• as a DDS using diclofenac sodium and indomethacin as the drugs. They reported the cumulative release of diclofenac sodium from the monoliths lower than 5% at pH 1.2 and higher than 70% at pH 7.4. In addition, they reported cumulative release 6% of indomethacin within the first hour in phosphate

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

• - and mesostructures in larger-scale photoreactors, such as packed beds and monoliths coated with catalysts can also enhance the mass transfer and operate at microreactor reaction rates. Together with photomicroreactors, these structured reactors are opening a new era in photochemistry by providing a

• reaction conditions, the flow needs to be distributed to all photoreactor units uniformly. In heterogeneous reactions, the flow field also affects the mass transport significantly. Structures such as beads or monoliths are frequently used to enhance the mass transfer, which in turn affects the flow field

• reaction rate [49]. Structures are commonly used to alleviate the mass transport effects. Catalysts are usually coated on beads [15][50][51], monoliths [52][53][54], or foams [55]. Beads coated with catalyst are often used in packed bed photoreactors. Schematic representations of a packed bed photoreactor

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

• quantum yield of 4.6% upon irradiation at 410 nm. Furthermore, as a proof of concept two different device setups of commercially available UV light emitting diodes, are coated with silica monoliths containing the three triethoxysilylpropyl-substituted fluorophore derivatives. These coatings are able to

• convert the emitted UV light into light with correlated color temperatures of very cold white (41100 K, 10700 K) as well as a greenish white emission with correlated color temperatures of about 5500 K. Keywords: benzofurazane; LED; luminophores; mesoporous silica hybrids; monoliths; Nile red; perylene

• as transparent monoliths in different shapes [17][18][19]. Here, we communicate our first efforts to design red, green, and blue light-emitting mesoporous materials from organic chromophores, their blending to white light-emitting silica hybrids based upon additive color mixing, and as a proof of

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

• structural components distinguishable by optical microscopy” [102]. According to this definition, honeycombs do not fall within this category. In the recent years, porous monoliths have attracted considerable interest in several flow-through applications for the fine chemistry, including chromatography and

• catalyst productivity and selectivity [105][106]. Particularly, monoliths featuring a 3D isotropic, hierarchically porous network of narrowly size distributed, interconnected macropores (1–30 μm) and mesopores within the struts (6–50 nm) have shown a unique hydrodynamic behavior in the liquid phase [107

• [111] with a high permeability typical of macropores, which results in a very efficient mass transfer [112]. According to Darcy’s law, describing the flow of a fluid through a porous medium, hierarchically porous monoliths show a very low pressure drop Δp per unit reactor length L (Δp/L = (μv)/k, μ

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• catalysts also lend themselves particularly well to continuous processing. One such example is reported by Karbass et al. [26], who carried out continuous flow reaction using Pd(0) derived from [Pd3(OAc)6] supported on polymeric monoliths containing methylimidazole, an ionic-liquid (IL) moiety in near

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

• 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

• ][22]. Originally monoliths were developed to facilitate the isocratic separation of peptides [17][23]; however, our group and others have shown interest in using monolithic supports to facilitate key chemical transformations [24][25][26][27][28][29][30][31][32][33][34][35]. The above advantages of

• be potential intermediates in the Appel reaction [58][59] and consequently we also wished to investigate the interplay between the two reaction mechanisms. Results and Discussion Formation of the triphenylphosphine monolith The triphenylphosphine monoliths for the Ramirez reactions were formed using

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

• beads related to the solvent employed. To circumvent some of the issues with bead-type supports, monoliths have been developed as replacements for use in continuous-flow synthesis. Monoliths are a single continuous piece of uniformly porous material prepared by precipitation polymerisation of a

• over a wide range of solvents and under reasonable pressure due to the high degree of cross linking, making them easier to use in flow processes. Historically monoliths have traditionally been used to facilitate the isocratic separation of peptides [19]; however, our group and others have shown

• rate of reaction observed as well as to circumvent problems associated with the use of bead-based immobilised reagents in continuous flow. Results and Discussion Formation of the triphenylphosphine monolith The triphenylphosphine monoliths were formed by precipitation polymerisation of the appropriate

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

• comparable pore diameters and surface areas, were fabricated with diameters of 3.2 and 6.4 mm to give volumetric capacities of 0.205 and 0.790 mL, respectively. The two monoliths were functionalized with a loading of 4.5 wt % Pd and then sealed in heat-shrinkable Teflon® tubing to form a monolithic flow

• -functionalized monoliths in a flow microreactor, is the achievement of an efficient coupling of the microwave energy, which will be a function of both the absorbing species present and of the penetration depth of microwave irradiation into the reaction zone [17]. This is especially important in flow systems

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

• the nanoparticle type and content. Moreover, the reinforced monoliths were tested for the possible use as scaffold materials in tissue engineering, by carrying out cell cultivation experiments with human adipose tissue-derived stromal cells. Keywords: hybrid materials; monoliths; nanoparticles; ring

• osteoinductive and provide mechanical support when needed [15]. As an alternative to poly(NBE)-based monoliths, we investigated the preparation of monolithic structures from a highly polar cyclooctene derivative. So far, ROMP-derived monolithic materials have successfully been applied to separation science as

• well as heterogeneous catalysis [16][17][18]. Generally, cyclooctene-derived monoliths differ from their NBE-based counterparts in that they are less prone to oxidation and display higher elastic moduli. With the aim to synthesize organic-inorganic monolithic hybrid materials for application as