Authors:Gary Perkins, Omar Khatib, Matthew Peterson, Annukka Kallinen, Tien Pham, Alison Ung, Ivan Greguric and Giancarlo Pascali
Carbon dioxide chemistry is an area of continuing growth in recent times, due to socioeconomic and environmental reasons. Several methods have now been reported for obtaining N-methylation on primary and secondary amines directly from CO2. We have translated in two microfluidic setups (Slug Flow [SF] and Tube-in-Tube [TiT]) a ruthenium (Ru)-catalyzed process previously reported using a pressure vessel. Here, we demonstrate how the SF approach is more efficient but requires more input to reach a steady state, while the TiT system is less efficient but more tuneable.We have tested these processes on three model amines and two radiopharmaceutical precursors that are routinely used in 11C chemistry. The microfluidic processes tested are also potentially more efficient than the pressure vessel counterpart, in terms of amount of Ru catalyst needed (1% vs. 10%) and projected reaction completion time.
Authors:Viktor Misuk, Andreas Mai, Konstantinos Giannopoulos, Dominik Karl, Julian Heinrich, Daniel Rauber and Holger Löwe
The method of combining the concept of fluorous biphasic catalysis (FCB) with micro multiple emulsions benefits from the advantages of homogeneous as well as from heterogeneous catalysis in continuous micro flow. In this particular case, three immiscible fluid phases in continuous micro segmented flow were used to perform palladium-catalyzed Heck cross-coupling reactions of styrene with aryl halides. A capillary tube-in-tube coaxial flow setup in combination with a glass micro reactor was used to produce monodisperse aqueous phase/organic phase/perfluorinated phase double emulsions. The resulting emulsions had a core–shell droplet structure composed of a perfluorcarbon fluid in which a palladium catalyst with fluorinated phosphine ligands was dissolved, an organic phase consisting of a solvent and two reagents, and an alkaline aqueous solution. The fluorous and organic phases of the double emulsion form a thermomorphous system which can be converted into one phase by an increase of temperature above 150 °C, and the catalytic reaction is performed temporarily. By decreasing the temperature, a phase separation takes place; after that, the organic phase contains the product and the catalyst is located in the fluorous phase. The separated catalyst solution was reused several times without a noticeable loss of activity. The main advantage of this method is to use temporarily very high catalyst concentrations in each droplet, while employing only small amounts of the catalyst for the overall reaction volume.
Authors:Viktor Misuk, Andreas Mai, Yuning Zhao, Julian Heinrich, Daniel Rauber, Konstantinos Giannopoulos and Holger Löwe
Fast mixing is essential for many microfluidic applications, especially for flow at low Reynolds numbers. A capillary tube-in-tube coaxial flow setup in combination with a glass microreactor was used to produce immiscible multiphase segments. These double emulsion segments are composed of an organic solvent as the shell (outer) phase and a completely fluorinated liquid (Fluorinert® FC-40) as the core (inner) phase. Due to the higher density of the core droplets, they are responsive to changing their position to the force of gravity (g-force). By gently shaking or jiggling the reactor, the core drop flows very fast in the direction of the g-field without leaving the shell organic phase segment. Furthermore, by shaking or jiggling the reactor, the inner droplet moves along the phase boundary of the shell segment and continuous phase. Computational fluid dynamics (CFD) calculations show an enhancement of the internal circulations, i.e., causing an exceptional mixing inside of the shell segment. For reactions which are limited by mass transfer, where the conversion significantly increases with improved mixing, these recirculation zones are decisive because they also accelerate the mixing process. With a common phase-transfer catalytic (PTC) etherification of phenol with dimethyl sulphate, a remarkable increase of yield (85% gas chromatography [GC]) could be achieved by applying active mixing within a segment in continuous flow.
in a gas–liquid multiphase tube-in-tube reactor” B. Tomaszewski, R. C. Lloyd, A. J. Warr, K. Buehler, A. Schmid* ChemCatChem 2014 , 6 , 2567–2576
“Controllable preparation of nano-CaCO 3 in a microporous tube-in-tube
-flow conditions” S. Grego , F. Aricò , P. Tundo * Organic Process Research and Development 2013 , 17 , 679 – 683 .
“Mass transport and reactions in the tube-in-tube reactor” L. Yang , K. F. Jensen * Organic Process Research and
. Soós* European Journal of Organic Chemistry 2013 , 4490 – 4494 .
“Fluorenylmethoxycarbonyl-N-methylamino acids synthesized in a flow tube-in-tube reactor with a liquid–liquid semipermeable membrane” A. E. Buba , S. Koch
furfural and 5-(hydroxymethyl)furfural ” D. Scholz , C. Aellig , I. Hermans * ChemSusChem 2014 , 7 , 268 – 275 .
“ Tube-in-tube reactor as a useful tool for homo- and heterogeneous olefin metathesis under continuous flow mode
using a Teflon AF-2400 tube-in-tube reactor: Synthesis of thioureas and in-line titrations ” D. L. Browne , M. O'Brien , P. Koos , P. B. Cranwell , A. Polyzos , S. V. Ley * Synlett 2012 , 1402 – 1406 .
“ Continuous flow
Authors:Dong-Hyeon Ko, Ki-Won Gyak and Dong-Pyo Kim
the structure offers such as wetting and gating properties.
In the case of microfluidic configuration for efficient separation, two distinct schemes have been utilized for continuous flow process: tube-in-tube system [ 42 – 44 ] and dual
Authors:Bartholomäus Pieber, Kerry Gilmore and Peter H. Seeberger
–liquid) systems. More advanced versions of these reactors are often utilized when gases are employed, in particular membrane-based reactor setups such as the tube-in-tube reactor [ 31 ]. Here, a homogeneous (saturated) solution of the respective gas in the