Process intensification on rotating surfaces controlling chemical reactivity and selectivity

[Truncated] A rotating microfluidic device namely, the vortex fluidic device (VFD) as a form of process intensification, has been optimised and applied in different organic syntheses. This device allows for the synthesis of molecules that are not usually accessible or are only accessible with limited practical convenience using conventional methods. The low cost VFD, which has a rapidly rotating tube open at one end, forms dynamic thin films at a high rotating speed. Dual operation modes, controlled residence times and variable parameters of this device make it very effective and efficient for different types of organic syntheses. In the ‘confined mode’ of operation, intense shear is generated in the resulting thin films for finite sub-millilitre volumes of liquid, depending on the speed, tilt angle of the tube, and other operating parameters of the VFD. It can also operate under the ‘continuous flow mode’ with jet feeds delivering liquids into the rotating tube where additional shear is generated in the thin films from the viscous drag as the liquid whirls along the tube. Diels-Alder dimerisations of cyclopentadiene and methyl cyclopentadiene were used as model reactions for optimising the operational parameters of the VFD. The results of the optimised conditions of the dimerisation reactions have been translated into other organic reactions. Generally the results establish that dramatic control of reactivity and selectivity can be achieved using the VFD, which highlights the versatility of this device.

Amino functionalized 2,4,6-triarylpyridines were deemed as important precursors for G-quadruplex DNA binding ligands. A synthetic route to access these compounds under continuous flow (through 1,5-diketone precursor) has been developed in the VFD, overcoming a series of competing reactions and effectively controlling chemical reactivity and selectivity. This device also overcomes the multiple passes involved in using the spinning disc processor (SDP) due to the longer residence time that is able to be achieved relative to the SDP. The one pot reaction of amino-functionalized 2,4,6- triarylpyridines has also been established using the continuous flow mode of the VFD in a single pass, in the presence of ammonium acetate and PEG. A synthetic route to access chalcones has also been developed by changing both, the parameters of the VFD and the ratio of the starting materials used.