Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

• Rajesh Munirathinam,
• Roberto Ricciardi,
• Richard J. M. Egberink,
• Jurriaan Huskens,
• Michael Holtkamp,
• Herbert Wormeester,
• Uwe Karst and
• Willem Verboom

Beilstein J. Org. Chem. 2013, 9, 1698–1704, doi:10.3762/bjoc.9.194

• Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and

• X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a

• model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3. Keywords: dehydration of oximes; flow chemistry; gallium; microreactors; Lewis acid catalysis

Chemistry in flow systems III

• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1696–1697, doi:10.3762/bjoc.9.193

• synthetic examples. The combined work of experts from engineering and chemical synthesis was highly fruitful and is so until today. This combination of expertise has catalyzed the development of microreactor technology in the applied context of synthesis and production. Chemical engineers depend on input

Controlled synthesis of poly(3-hexylthiophene) in continuous flow

• Helga Seyler,
• Jegadesan Subbiah,
• David J. Jones,
• Andrew B. Holmes and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2013, 9, 1492–1500, doi:10.3762/bjoc.9.170

• Suzuki–Miyaura and Stille coupling [12]. In this study, the continuous-flow synthesis of P3HT is examined. Distinct from a recent report of P3HT synthesis in a droplet-based microreactor [20], development of the flow synthesis is described in detail and controlled polymerization of P3HT, both in terms of

Hypervalent iodine/TEMPO-mediated oxidation in flow systems: a fast and efficient protocol for alcohol oxidation

• Nida Ambreen,
• Ravi Kumar and
• Thomas Wirth

Beilstein J. Org. Chem. 2013, 9, 1437–1442, doi:10.3762/bjoc.9.162

• successfully achieved by using microreactor technology. This method can be used as an alternative for the oxidation of various alcohols achieving excellent yields and selectivities in significantly shortened reaction times. Keywords: alcohols; carbonyl compounds; flow chemistry; microreactor; oxidation

• platforms to perform reactions under continuous flow rather than in batch mode has led to improvements regarding safety and sustainability. Microreactor technology can be beneficial over classical approaches in a variety of chemical reactions. Many reactions can benefit from the properties of microreactors

• shortened reaction times. Several other oxidative processes have already been reported in flow chemistry [16]. Results and Discussion Benzyl alcohol was chosen as a substrate in order to examine the efficiency of the reaction and the microreactor flow system. In a batch reaction, the mixture of benzyl

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• footage was used by Jensen and co-workers to investigate metal aggregation in a palladium-catalysed cross-coupling reaction [52], this time within a microreactor where such aggregation can lead to pressure spikes and reactor plugging (Figure 9). Data collected using this monitoring technique allowed them

Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• concept to avoid the epimerization of reactive intermediates, which has allowed them to carry out the enantioselective version of the above procedure. Thus, the use of a flow microreactor system has allowed the enantioselective carbolithiation of conjugated enynes, followed by the reaction with

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• demonstrated that the photon efficiency of the reaction could be improved through the use of a 15 W black light and a quartz-plate-covered microreactor [24]. Although faster reaction times are claimed for the microflow system as compared to batch, it is probably unrealistic to compare reaction completion times

• [2 + 2] photocycloadditions have also been performed by using microflow apparatus. Mizuno et al. reported the reaction shown in Scheme 2 using a Xe lamp (λ > 290 nm) in a poly(dimethylsiloxane) reactor [25]. The microreactor was compared with a batch reactor and was found to give slightly better

• , attempts to achieve high conversions always increased the proportion of product 6 [26]. Use of the microreactor proved to be an advantage in this situation as compound 5 was removed as it was formed and was not exposed to further irradiation. In this way high selectivity (96:4) could be achieved in flow

Continuous-flow catalytic asymmetric hydrogenations: Reaction optimization using FTIR inline analysis

• Magnus Rueping,
• Teerawut Bootwicha and
• Erli Sugiono

Beilstein J. Org. Chem. 2012, 8, 300–307, doi:10.3762/bjoc.8.32

• : asymmetric reduction; binolphosphoric acid; Brønsted acid; Hantzsch dihydropyridine; IR spectroscopy; real-time analysis; Introduction In recent years, a growing interest in microreactor technology has been seen in the scientific community and the development of microfabricated reaction systems is actively

• pursued. Microreactor technology offers numerous advantages, including precise control of reaction variables, enhanced mixing quality, improved operational safety, reduced reagent consumption and ready scale-up of chemical processes. Due to the high surface-area-to-volume ratios of microstructured

• example of a continuous-flow organocatalytic asymmetric transfer hydrogenation performed in a microreactor. In this work a ReactIR flow cell was coupled with the microreactor and applied as an inline monitoring device for optimizing the reactions. Results and Discussion The continuous-flow microreactor

Continuous proline catalysis via leaching of solid proline

• Suzanne M. Opalka,
• Ashley R. Longstreet and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2011, 7, 1671–1679, doi:10.3762/bjoc.7.197

• . Keywords: aminoxylation; flow chemistry; heterogeneous catalysis; packed-bed microreactor; proline/thiourea catalysis; Introduction Continuous flow chemistry [1][2][3], performed in small dimension tubing or channels, differs from batch chemistry in that mixing and heat transfer are significantly faster

Coupled chemo(enzymatic) reactions in continuous flow

• Ruslan Yuryev,
• Simon Strompen and
• Andreas Liese

Beilstein J. Org. Chem. 2011, 7, 1449–1467, doi:10.3762/bjoc.7.169

• ). The coupled reaction is carried out in a continuously operated packed-bed microreactor. As compared to the batch-mode experiments, higher concentrations of H2O2 were applied without detectable catalyst deactivation after 24 hours. At 100% conversion, a space-time yield of 646 g L−1 day−1 was obtained

Multistep flow synthesis of vinyl azides and their use in the copper-catalyzed Huisgen-type cycloaddition under inductive-heating conditions

• Lukas Kupracz,
• Jan Hartwig,
• Jens Wegner,
• Sascha Ceylan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2011, 7, 1441–1448, doi:10.3762/bjoc.7.168

• microreactor [32]. A key benefit of this technology is that the copper metal is directly and instantaneously heated inside the reactor, which results in a higher reactivity than with conventionally heated elemental copper [32]. These results prompted us to investigate the reaction of vinyl azides 4 in the

Translation of microwave methodology to continuous flow for the efficient synthesis of diaryl ethers via a base-mediated S_NAr reaction

• Charlotte Wiles and
• Paul Watts

Beilstein J. Org. Chem. 2011, 7, 1360–1371, doi:10.3762/bjoc.7.160

• ® S1) was employed for the continuous flow synthesis of diaryl ethers at 195 °C and 25 bar, affording a reduction in reaction time from tens of minutes to 60 s when compared with a stopped-flow microwave reactor. Keywords: automated synthesis; continuous flow; microreactor; microwave; nucleophilic

• the potential to be more efficient. The quantity of material generated can therefore be determined by the length of continuous operation and not by the number of “batches” performed. To perform the flow reactions, the microreactor development apparatus Labtrix® S1 (Chemtrix BV, NL), illustrated in

• Figure 2, was employed. The heart of the system is a glass microreactor that is positioned on a thermally regulated stage, which enables reactions to be performed between −15 and 195 °C. Reagent solutions are delivered to the reactor through a series of syringe pumps (0.1 to 25 µL·min−1) and the system

Koch–Haaf reaction of adamantanols in an acid-tolerant hastelloy-made microreactor

• Takahide Fukuyama,
• Yu Mukai and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2011, 7, 1288–1293, doi:10.3762/bjoc.7.149

• : continuous flow system; hastelloy; Koch–Haaf reaction; microreactor; Introduction The recent evolution of microreactor technology has allowed synthetic chemists to use this precisely sophisticated reaction apparatus in place of the well-established glassware batch flask [1][2][3][4][5][6][7][8][9][10

• causes a serious problem especially for large scale synthesis. Herein, we report that the Koch–Haaf reaction in a microflow reactor can be carried out at room temperature without any cooling equipment. The employed hastelloy-made microreactor system was compatible with corrosive (strongly acidic

Triple-channel microreactor for biphasic gas–liquid reactions: Photosensitized oxygenations

• Ram Awatar Maurya,
• Chan Pil Park and
• Dong-Pyo Kim

Beilstein J. Org. Chem. 2011, 7, 1158–1163, doi:10.3762/bjoc.7.134

• Korea, Fax: (+82)-42-823-6665 10.3762/bjoc.7.134 Abstract A triple-channel microreactor fabricated by means of a soft-lithography technique was devised for efficient biphasic gas–liquid reactions. The excellent performance of the microreactor was demonstrated by carrying out photosensitized

• oxygenations of α-terpinene, citronellol, and allyl alcohols. Keywords: gas–liquid reaction; microreactor; photosensitization; singlet oxygen; Introduction Microreactors have recently attracted much interest among the scientific community for performing laboratory operations on small scales [1][2][3][4][5][6

• -volume ratio. Therefore, vigorous stirring, ultrasonic agitation, high pressure or supercritical conditions are typically applied to enhance mass transfer in batch reactors for gas–liquid biphasic reactions. Recently, we reported a dual-channel microreactor that dramatically improved the reaction rate of

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

• ][5][6][7]. Much of this work has focused on continuous-flow microreactor methodology for laboratory based organic synthesis, and has featured the development of inorganic and organic polymer based functionalized monolithic reactors that can operate at elevated temperatures and under high pressure [8

• -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

• maintaining the intrinsic benefits of the reaction geometry offered when using microreactor methodology. In this work we report a simple and effective approach for achieving volumetric scalability in a flow reaction system through the use of Pd-supported silica-based monolithic reactors coupled with microwave

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• Kevin Watts William Gattrell Thomas Wirth Cardiff University, School of Chemistry, Park Place, Cardiff CF10 3AT, UK Prosidion Ltd, Watlington Road, Oxford OX4 6LT, UK 10.3762/bjoc.7.127 Abstract A microreactor for electrochemical synthesis has been designed and fabricated. It has been shown that

• different reactions can be carried out successfully using simple protocols. Keywords: diaryliodonium compounds; electrochemistry; flow chemistry; microreactor; Introduction Electrochemical reactions offer a clean route to the formation of anion and cation radical species from neutral organic molecules

• the electrodes overlap or become "coupled". This allows ions to be electrogenerated and play the role of the supporting electrolyte. Different microreactor systems have already been developed for chemistry in this area and have been successfully employed in the conduction of electrochemical reactions

Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl₃ promoted homocoupling

• Aiichiro Nagaki,
• Yuki Uesugi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2011, 7, 1064–1069, doi:10.3762/bjoc.7.122

• homocoupling of aryllithiums, and this enabled its integration with the halogen–lithium exchange reaction of aryl halides in a flow microreactor. This system allows the homocoupling of two aryl halides bearing electrophilic functional groups, such as CN and NO2, in under a minute. Keywords: homocoupling; iron

• salts; microreactor; organolithiums; Introduction Biaryl structures often occur in various organic compounds including natural products, bioactive compounds, functional polymers, ligands in catalysts and theoretically interesting molecules, and the oxidative homocoupling of arylmetals is one of the

• aryllithiums, especially of those bearing electrophilic functional groups such as cyano and nitro groups [21], making the subsequent homocoupling difficult or impossible. Recently, we have reported that flow microreactor systems [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides

• Oksana Shvydkiv,
• Kieran Nolan and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121

• superior results thus proving the superiority of microphotochemistry over conventional technologies. Keywords: microflow; microreactor; photochemistry; photodecarboxylation; phthalimide; Introduction Organic photochemistry is a highly successful synthesis method that allows the construction of complex

• [20][21][22][23] and specialized micro-photoreactors for laboratory- to technical-scale synthesis have been developed [24][25][26]. We have recently reported on acetone-sensitized photodecarboxylation (PDC) reactions of phthalimides in a commercially available microreactor [27]. The photochemistry of

• mm and a total volume of 1.68 mL. The reaction mixture was loaded into a programmable syringe pump, degassed with nitrogen, pumped through the microreactor (flow rate: 0.028 mL/min) and collected in a flask outside the irradiated area. In a parallel series of experiments, a conventional Rayonet

Continuous gas/liquid–liquid/liquid flow synthesis of 4-fluoropyrazole derivatives by selective direct fluorination

• Jessica R. Breen,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• Jonathan Fray and
• Bhairavi Patel

Beilstein J. Org. Chem. 2011, 7, 1048–1054, doi:10.3762/bjoc.7.120

• manufacturing, we developed continuous flow microreactor systems that enabled gas/liquid fluorination reactions between fluorine and various substrates to occur in very efficient processes [19][20][21]. Fluoro-carbonyl derivatives can, in principle, be utilised as building blocks for the preparation of more

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• problems and disadvantages. In our laboratory, PI catalysts were applied to tri-phase hydrogenation reactions in a microreactor system and led to markedly shorter reaction times [11]. While the productivity of a single microreactor is low, increasing the number of reactors (“numbering up”) could readily

• recovered and re-used in hydrogenation reactions in batch systems. We then developed polysilane-supported Pd/metal oxide hybrid catalysts [13] using the PI method (microencapsulation and cross-linking), which were then applied in these microreactor systems [14]. The hybrid catalysts were insoluble, did not

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

• Chemistry, Karl-Franzens-University Graz, Universitätsplatz 1, A-8010 Graz, Austria Continuous Flow/Microreactor Technologies, Lonza AG, CH-3930 Visp, Switzerland 10.3762/bjoc.7.59 Abstract The decomposition of 5-benzhydryl-1H-tetrazole in an N-methyl-2-pyrrolidone/acetic acid/water mixture was

• 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

• -temperature batch conditions obtained in sealed Pyrex glass reaction vessel (using either conventional or microwave heating) [25] to a continuous flow format. The microreactor system used for these studies was a high-temperature, high-pressure microtubular flow unit that can be used for processing homogeneous

Acid- mediated reactions under microfluidic conditions: A new strategy for practical synthesis of biofunctional natural products

• Katsunori Tanaka and
• Koichi Fukase

Beilstein J. Org. Chem. 2009, 5, No. 40, doi:10.3762/bjoc.5.40

• prominent biological activity in a “practical” and a “industrial” manner. Keywords: acid-mediated reaction; microreactor; natural products synthesis; oligosaccharide; pristane; Introduction A continuous flow microreactor, an innovative technology, has been used to realize efficient mixing and fast heat

• problems, we used a continuous flow microreactor. An application of the microfluidic system to the glycosylation reaction was first reported by Seeberger and co-workers on α-mannosylation [18]. We also have established an efficient microfluidic glycosylation in combination with the affinity separation

• the synthetic procedure, therefore, we used a continuous flow microreactor. Optimal conditions for reductive opening of 4,6-O-benzylidene acetals by a microfluidic system, similar to the α-sialylation and the β-mannosylation protocols, were examined using the glucose 4,6-O-benzylidene acetal 7 (Table

Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)

• Gjergji Shore,
• Michael Tsimerman and
• Michael G. Organ

Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35

• ., Bruker Biospin Inc., and York University. The authors are grateful to Biotage Inc. for the donation of a Smith Creator Synthesizer™ and to Syrris Inc. for the donation of the components of an AFRICA microreactor flow system to develop this new methodology. We acknowledge Ross Davidson at Surface Science

Radical carbonylations using a continuous microflow system

• Takahide Fukuyama,
• Md. Taifur Rahman,
• Naoya Kamata and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2009, 5, No. 34, doi:10.3762/bjoc.5.34

• pressurized carbon monoxide gas. Good to excellent yields of carbonylated products were obtained via radical formylation, carbonylative cyclization and three-component coupling reactions, using tributyltin hydride or TTMSS as a radical mediator. Keywords: continuous flow system; microreactor; radical

Controlling hazardous chemicals in microreactors: Synthesis with iodine azide

• Johan C. Brandt and
• Thomas Wirth

Beilstein J. Org. Chem. 2009, 5, No. 30, doi:10.3762/bjoc.5.30

• reaction conditions in microreactors. Keywords: azide; flow chemistry; hazardous reagents; microreactor; rearrangement; Introduction Microstructured devices have already found their way into organic synthesis, because they offer various advantages over traditional large-scale chemistry performed in

• other functional groups [5]. Iodine azide is a very hazardous but valuable reagent that is easier and much more safely handled under microreactor conditions. Iodine azide is a solid compound, highly explosive and toxic. It is known to add stereospecifically to carbon–carbon double bonds with high

• 1 was added to the reagent in the microreactor as shown in Figure 1. All reagents and the aldehyde 1 were used as solutions in acetonitrile. After mixing the aldehyde with the iodine azide reagent the solution is passed through a capillary (volume: 196 µL) in a heating zone to allow the Curtius