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Tagged Phosphine Reagents to Assist Reaction Work-up by Phase-Switched Scavenging Using a Modular Flow Reactor Process
The use of three orthogonally tagged phosphine reagents to assist chemical work-up via phase-switch scavenging in conjunction with a modular flow reactor is described. These techniques (acidic, basic and Click chemistry) are used to prepare various amides and tri-substitutedguanidines from in situ generated iminophosphoranes.
Tagged Phosphine Reagents to Assist Reaction Work-up by Phase-Switched Scavenging Using a Modular Flow Reactor Process
C.D. Smith, I.R. Baxendale, G.K. Tranmer, M. Baumann, S.C. Smith, R.A. Lewthwaite and S.V. Ley, Org. Biomol. Chem., 2007, 5, 1562-1568.
http://pubs.rsc.org/en/content/articlelanding/2007/ob/b703033a/unauth#!divAbstract
Continuous Flow Ligand-Free Heck Reactions Using Monolithic Pd[0] Nanoclusters
Continuous Flow Ligand-Free Heck Reactions Using Monolithic Pd[0] Nanoclusters
N. Nikbin, M. Ladlow, S.V. Ley, Org. Proc. Res. Dev., 2007, 11, 458-462.
http://pubs.acs.org/doi/abs/10.1021/op7000436
Flow-through reactor setup.
An automated reactor has been developed for performing ligand-free Heck reactions in continuous flow mode. The reactor utilises a monolithic reactor cartridge derivatised with Pd(0) nanoparticles in-line with a scavenging cartridge containing Quadrapure-TU to efficiently capture palladium residues and thereby afford Heck products directly in high purity.
Hydrogenation in flow: homogenous and heterogeneous catalysts using Teflon AF-2400 to effect gas-liquid contact at elevated pressure
http://pubs.rsc.org/en/Content/ArticleLanding/2011/SC/c1sc00055a#!divAbstract
M. O’Brien, N. Taylor, A. Polyzos, I.R. Baxendale, S.V. Ley, Chem. Sci. 2011, 2, 1250-1257.
A Tube-in-Tube reactor/injector has been developed, based on a gas-permeable Teflon AF-2400 membrane, which allows both heterogeneous and homogeneous catalytic hydrogenation reactions to be efficiently carried out at elevated pressure in flow, thereby increasing the safety profile of these reactions. Measurements of the gas permeation through the tubing and uptake into solution, using both a burette method and a novel computer-assisted ‘bubble counting’ technique, indicate that permeation/dissolution follows Henry’s law and that saturation is achieved extremely rapidly. The same gas-permeable membrane has also been shown to efficiently effect removal of excess unreacted hydrogen, thus enabling further downstream reaction/processing.
Flow chemistry approaches directed at improving chemical synthesis
The true potential of flow chemistry as an enabling technology can really only be fully appreciated when seen in the context of a target driven multi-step synthesis, aimed at the delivery of advanced chemical structures such as active pharmaceutical ingredients (APIs) .
As most pharmaceutical syntheses typically require between 8 and 10 chemical transformations (this is often somewhat reduced to 5/6 steps when analogue/library syntheses are being conducted), excluding protecting group manipulations, to realize the target molecule, this is a good foundation from which to explore the advantages of flow chemistry. We have generated a flow protocol for the synthesis of imatinib, the API of the Novartis block buster anticancer therapeutic Gleevec (imatinib mesylate), including a series of analogues (Scheme 11)
Furthermore, we aimed to create a route which would allow each of the three main fragments to be exchanged to address maximum variation in subsequent analogue synthesis. This requires additional planning to build flexibility into the sequence where this desired diversity can be easily introduced. Again, prior consideration of the generated intermediates, and any potential by-products that may arise, is critical and should be addressed prior to embarking on the synthesis.
Consequently, the extensive profiling of the reaction in terms of its purity profile is more closely analogous to process chemistry than traditional Medicinal Chemistry, even at the development stage. So, although more time consuming in the planning stage, having a greater understanding of the chemistry, does then enable a smoother up scaling and more rapid optimization of the route.
read all this at
http://www.degruyter.com/view/j/gps.2013.2.issue-3/gps-2013-0029/gps-2013-0029.xml
Flow chemistry approaches directed at improving chemical synthesis
1Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK
Corresponding author: Ian R. Baxendale, Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK
Citation Information: Green Processing and Synthesis. Volume 2, Issue 3, Pages 211–230, ISSN (Online) 2191-9550, ISSN (Print) 2191-9542, DOI: 10.1515/gps-2013-0029, May 2013
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