Automated solid-phase peptide synthesis to obtain therapeutic peptides

• Veronika Mäde,
• Sylvia Els-Heindl and
• Annette G. Beck-Sickinger

Beilstein J. Org. Chem. 2014, 10, 1197–1212, doi:10.3762/bjoc.10.118

• a batch-wise or a continuous-flow modus. The decision for a peptide synthesizer has to be made according to the intended application and thus, the scale (necessary amounts), the type of chemistry (Fmoc or Boc-strategy) and the number of reaction tubes (plates or vessels). The decision should also be

Integration of enabling methods for the automated flow preparation of piperazine-2-carboxamide

• Richard J. Ingham,
• Claudio Battilocchio,
• Joel M. Hawkins and
• Steven V. Ley

Beilstein J. Org. Chem. 2014, 10, 641–652, doi:10.3762/bjoc.10.56

• such as 4 are fully reduced. For maximum efficiency further hydrogenation procedures were carried out at the lower flow rate 0.1 mL min−1 and higher temperature 100 °C. In situ generation of the intermediate Performing an optimisation experiment in continuous flow – such as described in the previous

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

• Amol A. Kulkarni Chem. Eng. & Proc. Dev. Division, CSIR-National Chemical Laboratory, Pune – 411 008, India, phone: +91-20-25902153 10.3762/bjoc.10.38 Abstract This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has

• presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. Keywords: continuous flow; flow chemistry; nitration; nitric

• more of these limitations are experienced in every batch operation it is necessary to check their feasibility for continuous flow processing. Such transformations from batch to flow have been carried out for a lot of reactions and many continuous nitration plants of commercial scale exist. However, the

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

• the reaction with methyl acrylate the reactor was scaled from a 1.0 mm to 3.9 mm internal diameter and the conversion and turnover frequency determined. The results show that the Heck reaction can be effectively performed in scCO2 under continuous flow conditions with a palladium metal, phosphine-free

• catalyst, but care must be taken when selecting the reaction temperature in order to ensure the appropriate isomer distribution is achieved. Higher reaction temperatures were found to enhance formation of the branched terminal alkene isomer as opposed to the linear trans-isomer. Keywords: continuous flow

• cost and product contamination [3]. Further efforts have focused on the development of heterogeneous catalysts or immobilised homogeneous catalysts, particularly for use in continuous flow reactor systems [3][4][5][6]. The yield and selectivity of Heck reactions are profoundly influenced by a number of

Flow microreactor synthesis in organo-fluorine chemistry

• Hideki Amii,
• Aiichiro Nagaki and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2013, 9, 2793–2802, doi:10.3762/bjoc.9.314

• fluorine chemistry. Meanwhile, flow microreactor synthesis, the use of microfluidic devices, has emerged as a new method for producing chemical substances with high efficiency [11][12][13]. Now, the introduction of continuous-flow synthesis technique to laboratory synthesis represents a highly useful and

• conducted in one flow by adding the reagents at different places in continuous-flow synthesis [18][19][20][21][22][23][24][25]. This review deals with the successful examples on synthesis and reactions of fluorine-containing molecules by the use of flow microreactor systems. Useful applications using flow

• disproportionation to SF4 and explosive (Et2N)2SF2 when heating at over 90 °C [41][42][43]. Therefore, special care is required in handling a large quantity of DAST concerning the danger of the explosion under heating conditions. To solve these technical issues, the use of DAST in a continuous-flow reactor employing

Investigating the continuous synthesis of a nicotinonitrile precursor to nevirapine

• Ashley R. Longstreet,
• Suzanne M. Opalka,
• Brian S. Campbell,
• B. Frank Gupton and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2013, 9, 2570–2578, doi:10.3762/bjoc.9.292

• other value added structures that contain complex pyridines. The route terminates in a batch crystallization yielding high purity CAPIC. This outcome is expected to facilitate regulatory implementation of the overall process. Keywords: continuous; flow chemistry; HIV; Knoevenagel; nevirapine

A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

• Erli Sugiono and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 2457–2462, doi:10.3762/bjoc.9.284

• Erli Sugiono Magnus Rueping Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany 10.3762/bjoc.9.284 Abstract A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows

• dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities. Keywords: asymmetric transfer hydrogenation; binolphosphate; continuous-flow reactors; flow chemistry; microreactors; organocatalysis; photochemistry; Introduction Tetrahydroquinolines [1][2

• ][11][12][13][14][15][16][17]. In the past years, continuous-flow chemistry has received considerable attention and microstructured continuous-flow devices have emerged as useful devices for different chemical reactions [18][19][20][21][22]. Microreactor technology offers numerous practical advantages

Synthesis of homo- and heteromultivalent carbohydrate-functionalized oligo(amidoamines) using novel glyco-building blocks

• Felix Wojcik,
• Sinaida Lel,
• Alexander G. O’Brien,
• Peter H. Seeberger and
• Laura Hartmann

Beilstein J. Org. Chem. 2013, 9, 2395–2403, doi:10.3762/bjoc.9.276

• heteromultivalent glycosylation patterns by combining building blocks presenting different mono- and disaccharides. Keywords: continuous flow; flow chemistry: flow synthesis; glycoligands; multivalency; photochemistry; solid-phase synthesis; thiol–ene; thioglycosides; Introduction Multivalent carbohydrate ligand

• [20]. Carbohydrate conjugation was achieved by copper-catalyzed azide alkyne cycloaddtion (CuAAC) of carbohydrate ligands on alkyne presenting oligomers [21]. As an alternative conjugation approach to CuAAc, a very efficient thiol–ene coupling (TEC) [22][23][24][25] protocol in a continuous flow

• removal of the desired product minimizes unwanted secondary reaction pathways [27][28][29][30][31][32][33][34][35][36][37][38][39]. We also introduced the so-called building block approach in the context of thiol–ene coupling via the continuous-flow technique. A first example involved conjugating a

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• combined with the liberation of large amounts of gases such as nitric oxides and carbon dioxide which must be scrubbed from the system (Scheme 2). Interestingly, despite these considerations this method of synthesis is currently still run by the speciality chemicals company Lonza but now as a continuous

• flow process at their main plant in Visp, Switzerland. An alternative process is based on the availability of 3-picoline (1.15) which is generated as a major side product in the synthesis of pyridine prepared from formaldehyde, acetaldehyde and ammonia in a gas phase reaction (Scheme 3) [25]. The 3

Temperature measurements with two different IR sensors in a continuous-flow microwave heated system

• Jonas Rydfjord,
• Fredrik Svensson,
• Magnus Fagrell,
• Jonas Sävmarker,
• Måns Thulin and
• Mats Larhed

Beilstein J. Org. Chem. 2013, 9, 2079–2087, doi:10.3762/bjoc.9.244

• Uppsala, Sweden 10.3762/bjoc.9.244 Abstract In a continuous-flow system equipped with a nonresonant microwave applicator we have investigated how to best assess the actual temperature of microwave heated organic solvents with different characteristics. This is non-trivial as the electromagnetic field

• chemistry applications. Keywords: continuous-flow; flow chemistry; heating; microwave; organic synthesis; temperature; Introduction In organic synthesis, being able to accurately determine the reaction temperature is often of utmost importance [1][2][3]. When using conventional heating the reaction

• applicator for continuous-flow organic chemistry [17][18]. The current setup is depicted in Figure 1 and features a HPLC pump, a generator, a reactor cavity, an applicator and a Ø (ID) 3 mm × 200 mm borosilicate glass tube reactor. Nonresonant mode applicators has the advantage of avoiding hot and cold spots

Flow synthesis of a versatile fructosamine mimic and quenching studies of a fructose transport probe

• Matthew B. Plutschack,
• D. Tyler McQuade,
• Giulio Valenti and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 2022–2027, doi:10.3762/bjoc.9.238

• . Continuous flow synthesis of the key intermediate 1-amino-2,5-anhydro-D-mannose (3). Batch versus flow comparison. Supporting Information Supporting Information File 482: Experimental part. Acknowledgements Financial support from the Max Planck Society and the National Science Foundation (USA; CHE-1152020

• (100 °C) even though the reaction evolves large quantities of nitrogen gas. At a flow rate of 5 mL/min at 100 °C using a 10 mL reactor (2 min residence time), we achieved a throughput of 800 mg/min (Scheme 3). Table 1 shows a comparison between previously reported batch conditions and our continuous

• flow conditions and illustrates that this first step has a throughput more than 63-fold higher than the batch Tiffeneau–Demjanov conditions. The concentrated Tiffeneau–Demjanov reaction not only increased the throughput but also enabled oxime formation without the removal of water. Using excess

Microflow photochemistry: UVC-induced [2 + 2]-photoadditions to furanone in a microcapillary reactor

• Sylvestre Bachollet,
• Kimitada Terao,
• Shin Aida,
• Yasuhiro Nishiyama,
• Kiyomi Kakiuchi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2013, 9, 2015–2021, doi:10.3762/bjoc.9.237

• , Takayama-cho, Ikoma, Nara 630-0101, Japan 10.3762/bjoc.9.237 Abstract [2 + 2]-Cycloadditions of cyclopentene and 2,3-dimethylbut-2-ene to furanone were investigated under continuous-flow conditions. Irradiations were conducted in a FEP-microcapillary module which was placed in a Rayonet chamber

• chemistry; furanone; microflow chemistry; photochemistry; Introduction Continuous-flow chemistry has recently emerged as a new methodology in organic chemistry [1][2][3][4]. The combination of microstructured dimensions and flow operations has also proven advantageous for photochemical applications [5][6

• continuous-flow conditions [20][21][22]. In an extension of our previous work on furanones [10][23], we have now studied intermolecular photoadditions of alkenes to these compounds [24][25]. Direct and sensitized protocols have both been described (Scheme 1). Sensitized additions allow for irradiations in

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

• -substituted propargyl aldehydes undergo Hantzsch dihydropyridine synthesis in preference to Bohlmann–Rahtz reaction in a very high yielding process that is readily transferred to continuous flow processing. Keywords: Bohlmann–Rahtz; continuous flow processing; ethynyl ketones; flow chemistry; Hantzsch

• -mediated reactions still poses a number of challenges, in particular as a result of a lack of uniform heating [9]. Scale-up using batch methodologies in open reaction vessels can give excellent yields but might not be appropriate for certain volatile or toxic reagents whereas continuous flow processing

• , providing the reaction mixture is homogeneous, allows transfer from small-scale sealed vessel conditions to mesoscale production often without any modification of reaction conditions or loss in product yield [10]. The transfer from microwave batch reaction to continuous flow processing can offer many

Continuous flow photocyclization of stilbenes – scalable synthesis of functionalized phenanthrenes and helicenes

• Quentin Lefebvre,
• Marc Jentsch and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 1883–1890, doi:10.3762/bjoc.9.221

• Quentin Lefebvre Marc Jentsch Magnus Rueping Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany 10.3762/bjoc.9.221 Abstract A continuous flow oxidative photocyclization of stilbene derivatives has been developed which allows the scalable synthesis of

• backbone functionalized phenanthrenes and helicenes of various sizes in good yields. Keywords: continuous-flow reactor; flow chemistry; helicenes; light-driven cyclization reaction; photocyclization; stilbenes; Introduction Phenanthrenes are versatile intermediates toward polycyclic aromatic hydrocarbons

• visible light in the presence of a sensitizer [22], but, to the best of our knowledge, no reports on broadly applicable light-induced oxidative photocyclizations in flow are known. Herein, we report the first photocyclization of polysubstituted olefins using a continuous flow process and discuss

Raman spectroscopy as a tool for monitoring mesoscale continuous-flow organic synthesis: Equipment interface and assessment in four medicinally-relevant reactions

• Trevor A. Hamlin and
• Nicholas E. Leadbeater

Beilstein J. Org. Chem. 2013, 9, 1843–1852, doi:10.3762/bjoc.9.215

• Trevor A. Hamlin Nicholas E. Leadbeater Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, USA 10.3762/bjoc.9.215 Abstract An apparatus is reported for real-time Raman monitoring of reactions performed using continuous-flow processing. Its capability

• means of a calibration curve, determine product conversion from Raman spectral data as corroborated by data obtained using NMR spectroscopy. Keywords: flow processing; Raman spectroscopy; reaction monitoring; α,β-unsaturated carbonyl; Introduction Continuous-flow processing is used in the chemical

• interfacing a Raman spectrometer with a scientific microwave unit [31]. This has allowed us to monitor reactions from both a qualitative [32][33][34][35] and quantitative [36][37] perspective. A recent report of the use of Raman spectroscopy for monitoring a continuous-flow palladium-catalyzed cross-coupling

Ethyl diazoacetate synthesis in flow

• Mariëlle M. E. Delville,
• Jan C. M. van Hest and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2013, 9, 1813–1818, doi:10.3762/bjoc.9.211

• chemical synthesis is performed. In particular continuous-flow microreactor technology offers multiple advantages over batch chemistry, including the inherently safe conducting of reactions due to the small reactor dimensions, efficient heat transport and excellent control over the reaction conditions [6

• ][7][8]. While the synthesis of diazomethane has been extensively explored in batch [9] and in continuous-flow reactors [10][11], EDA is synthesized via different routes in batch [12][13], but relatively little is known about continuous-flow approaches [14]. Considering the importance of EDA in a wide

• variety of reactions e.g. cyclopropanation, X–H insertion, cycloaddition and ylide formation [13][15], and more recently, in the synthesis of valuable compound classes such as β-keto esters [16] and β-hydroxy-α-diazocarbonyl compounds [17], we aimed to develop an inherently safe continuous-flow EDA

Flow Giese reaction using cyanoborohydride as a radical mediator

• Takahide Fukuyama,
• Takuji Kawamoto,
• Mikako Kobayashi and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2013, 9, 1791–1796, doi:10.3762/bjoc.9.208

• precursors, ethyl acrylate as a radical trap, and sodium cyanoborohydride as a radical mediator, were examined in a continuous flow system. With the use of an automated flow microreactor, flow reaction conditions for the Giese reaction were quickly optimized, and it was found that a reaction temperature of

• 70 °C in combination with a residence time of 10–15 minutes gave good yields of the desired addition products. Keywords: continuous flow system; cyanoborohydride; flow chemistry; iodoalkanes; microreactor; tin-free Giese reaction; Introduction Organo halides are among the most useful precursors to

• automated microflow reactor [32], which revealed that running the continuous flow reactions at 70 °C for 10–15 min gave good yields of Giese addition products with effective suppression of the byproducts. Results and Discussion We employed an automated microflow reactor system, MiChS® System X-1 [33

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

[3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

• Stephan Cludius-Brandt,
• Lukas Kupracz and
• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1745–1750, doi:10.3762/bjoc.9.201

• the first photochemical transformation of vinyl azides to pyrrole derivatives under continuous-flow conditions. Only recently, we reported the two-step preparation of vinyl azides 1 in mircrostructured flow reactors starting from alkenes 6, using the solid-phase bound iodine azide transfer-reagent 7

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

• ; polymer brushes; Introduction Heterogeneous catalysis plays a crucial role in organic synthesis both in industry and academia. In the present situation, microreactors offer a number of benefits over classical setups [1][2][3]. Especially, heterogeneous catalysis in a continuous-flow microreactor is

• with gallium on the microchannel interior in the continuous flow-mode. The dehydration of cinnamaldehyde oxime (1, 25 µM in acetonitrile) was used as a model reaction to study the catalytic activity of the gallium-functionalized microreactor, at 90 °C and 5 atm pressure, generated using a back pressure

• regulator in continuous flow. The conversion of the reagent was monitored online by in-line UV–vis detection, measuring the decrease in the extinction of the solution of oxime 1 at 286 nm. The reaction times were varied by changing the flow rates between 1 and 26 µL·min−1. The reaction showed nearly

The rapid generation of isothiocyanates in flow

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 1613–1619, doi:10.3762/bjoc.9.184

• within a pseudo-/continuous flow process [11][12]. From a synthesis perspective the majority of these endeavours have been directed at enhancing specific reaction safety profiles, identifying new reaction sequences or generating improvements to well-known yet cumbersome transformations [13][14][15][16

Efficient continuous-flow synthesis of novel 1,2,3-triazole-substituted β-aminocyclohexanecarboxylic acid derivatives with gram-scale production

• Sándor B. Ötvös,
• Ádám Georgiádes,
• István M. Mándity,
• Lóránd Kiss and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1508–1516, doi:10.3762/bjoc.9.172

• acid derivatives in a simple and efficient continuous-flow procedure is reported. The 1,3-dipolar cycloaddition reactions were performed with copper powder as a readily accessible Cu(I) source. Initially, high reaction rates were achieved under high-pressure/high-temperature conditions. Subsequently

• safe and straightforward way. The obtained 1,2,3-triazole-substituted β-aminocyclohexanecarboxylates can be regarded as interesting precursors for drugs with possible biological effects. Keywords: β-amino acids; click chemistry; continuous-flow; copper; flow chemistry; triazoles; Introduction In

• frequently used as building blocks for the synthesis of new peptides and foldamers with possible biological effects [28]. Modern continuous-flow (CF) technologies offer many advantages over classical batch-based procedures [29][30][31][32], including efficient mixing quality [33], excellent heat and mass

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

• optimization of large area devices is costly and often impossible to achieve. Continuous-flow synthesis enables straight-forward scale-up of materials compared to conventional batch reactions. In this study, poly(3-hexylthiophene), P3HT, was synthesized in a bench-top continuous-flow reactor. Precise control

• : conjugated polymers; continuous-flow synthesis; controlled polymerization; flow chemistry; organic solar cell materials; Introduction Poly(3-hexylthiophene), P3HT, is the most investigated material in bulk heterojunction (BHJ) organic solar cells (OSC) [1]. The reasons for its dominance in the field include

• film quality. This will almost certainly create problems with the performance consistency of large-area roll-to-roll printed devices. To this end, we have started to examine some key reactions in the synthesis of organic electronic materials using continuous-flow processing [11][12][13]. Continuous

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

• 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

• . Enhanced mass- and heat transfer and short diffusion distances can lead to better yields within shorter reaction times [15]. Herein, we describe the development of continuous-flow systems using hypervalent iodine reagents in the TEMPO-mediated oxidation of alcohols with the advantage of significantly

• synthetic steps, without the need for isolation or purification of the intermediate aldehyde or ketone. Conclusion In conclusion, a highly efficient and selective continuous-flow reaction for the oxidation of different alcohols was developed. Apart from short reaction times, high conversions and excellent

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• peroxyl radical generated in situ is the real epoxidizing agent (Scheme 20). This protocol was successfully applied on a larger scale (1 liter Büchi glass vessel) for the synthesis of propylene oxide from the corresponding propene [56], and more recently under continuous-flow conditions, by means of a new