Flow Synthesis Online - September 2010
Welcome to the Flow Synthesis Online newsletter.
This publication is released bi-monthly and will showcase new applications, events, and equipment in the Flow Synthesis world.
Applications
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How to handle Organometallic Reagents
Organometallic reagents can present a challenge to the flow chemist, reacting readily with moisture or air that they come into contact with, and generating hard insoluble precipitates inside pumps and valves. But with the right approach, it is possible to handle these reagents in a stable and reliable fashion. |
Product News
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| Cooled Column Reactor now available
Earlier in the year Vapourtec launched a cooled tube reactor for homogeneous reactions down to -70oC.
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If this is the first issue of the newsletter that you've received, you might like to take a look at what you've missed in some previous issues. click here to see newsletter archive
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Events Attendees of the following events will be able to see the latest Vapourtec Flow Chemistry equipment in action, and no doubt talk to other users.
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| 1st RSC/SCI Symposium on Continuous Processing and Flow Chemistry
3-4 November, GlaxoSmithKline Stevenage, Herts, UK Herts, UK Click here for full details of this event.
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| UK Automated Synthesis Forum (UKASF)
17-18 November, Novartis, Horsham, UK
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Publications
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| A Palladium Wall Coated Microcapillary Reactor for Use in Continuous Flow Transfer Hydrogenation
1 Dept of Chem Eng, Univ of Cambridge A novel continuous flow multi-channel microreactor in which the internal surface has been functionalised with a palladium coating, enabling its use in catalytic heterogeneous liquid-phase reactions. The functional activity of the catalytic Pd layer was tested in a series of transfer hydrogenation reactions using triethylsilane as the hydrogen source. Click here to go straight to the publication
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| A Gram-Scale Batch and Flow Total Synthesis of Perhydrohistrionicotoxin
1CSIRO, Melbourne, Australia Biologically valuable histrionicotoxin spiropiperidine alkaloids are found in the Colombian poison arrow frog Dendrobates histrionicus shown in the illustration. The total synthesis of the spiropiperidine alkaloid (−)-perhydrohistrionicotoxin (perhydro-HTX) has been accomplished on a gram scale by employing both conventional batch chemistry as well as microreactor techniques. Click here to go directly to the publication
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| KMnO4-Mediated Oxidation as a Continuous Flow Process
Jorg Sedelmeier, Steven V. Ley, Ian R. Baxendale and Marcus Baumann Innovative Technology Centre, Department of Chemistry, University of Cambridge An efficient and easily scalable transformation of alcohols and aldehydes to carboxylic acids and nitroalkane derivatives to the corresponding carbonyls and carboxylic acids using permanganate as the oxidant within a continuous flow reactor is reported. Notably, the generation and downstream processing of MnO2 slurries was not found to cause any blocking of the reactor when ultrasound pulses were applied to the flow system. Click here to go straight to the publication
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| An Automated Microfluidic System for Online Optimization in Chemical Synthesis
Dept of Chemical Engineering, Novartis-MIT Center for Continuous Manufacturing, Cambridge, U.S.A. An automated, continuous flow system for the online, multivariable optimization of a chemical reaction is presented. Time and material required for an optimization trial are minimized by performing reactions in an integrated silicon microreactor and incorporating an HPLC for inline monitoring of the reaction performance. We use the system to optimize two different reactions to describe the potential impact of this system for reaction development. First, we demonstrate the broad operation capabilities by incorporating several feedback algorithms to optimize a weighted objective function involving the yield and the throughput of a Knoevenagel condensation reaction. After illustrating how system operations can be adapted for individual reactions, we perform a multiparameter optimization to maximize the yield of benzaldehyde in the oxidation pathway of benzyl alcohol to benzaldehyde to benzoic acid. A significant feature of the automated system is the ability to perform “black-box” optimization where no a priori information of the reaction parameters is required. Click here to go straight to the publication
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| Efficient Synthesis of 1,3-Dialkylimidazolium-Based Ionic Liquids: The Modified Continuous Radziszewski Reaction in a Microreactor Setup
Institute for Technical Chemistry and Environmental Chemistry, By making use of a modified Radziszewski reaction, it is demonstrated that water-soluble 1,3-dialkylimidazolium-based ionic liquids can be produced in good yields (70−90%) and purities (>95%) starting from readily available, cost-effective monoalkylamines, glyoxal, formaldehyde, and mineral or organic acids. The homosubstituted 1,3-dialkylimidazolium salts feature high thermal stabilities similar to those of their heterosubstituted counterparts, and relatively low viscosities, thus fulfilling the requirements for solvent application. The effect of various parameters has been studied with the goal of improving yields for both the batchwise and continuous synthesis (making use of a microreactor setup), allowing for the production of a wide variety of ionic liquids and the introduction of functionalities. The applicability of these ionic liquids is demonstrated on the example of cellulose dissolution and the dehydration of fructose to 5-hydroxymethylfurfural. Click here to go straight to the publication
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| Continuous flow multi-step organic synthesis (Review)
Novartis-MIT Center for Continuous Manufacturing, Cambridge, USA Using continuous flow techniques for multi-step synthesis enables multiple reaction steps to be combined into a single continuous operation. In this mini-review we discuss the current state of the art in this field and highlight recent progress and current challenges facing this emerging area. Click here to go straight to the publication
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| Effect of phase transfer chemistry, segmented fluid flow, and sonication on the synthesis of cinnamic esters
Department of Medicinal Chemistry, NiKem Research Srl, Milan, Italy Wittig reaction under Phase Transfer conditions was performed in a flow reaction system. Different bases, aldehydes, phosphonium salts, and flow reaction parameters were investigated, in absence of a phase transfer catalyst. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath.
Click here to go straight to the publication
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