Iodine-mediated electrocatalysis assist Annulation/cyclization via Intramolecular Benzylic C–H Amination: Batch vs Flow Electrochemistry

The access of heterocyclic compounds via direct amination of C-H bonds are of vital interest because of their role in pharmaceutical and natural products. The combination of molecular iodine and electricity activates benzylic C-H bond and facilitates the amination process via intramolecular C-N bond formation. Iodine works as a mediator for the formation of C-N bond via activation of a distance C-H bond through intermediate N-I bond under electrochemical conditions, so iodine can be called electrocatalyst. Under both batch & flow electrochemistry conditions, similar results were obtained in cyclization product with 77 & 78% yields respectively. However, in case of annulation reaction higher yield was obtained with 99% conversion under flow electrochemical conditions using our design of home-made flow microreactor. In both electrochemical transformations, cyclization as well as annulation reaction, no photocatalyst was used. Notably, flow reactions work under safe & environmentally friendly conditions, and continuous products are obtained.

Electrocatalytic C(sp3)–H/C(sp)–H cross-coupling in continuous flow through TEMPO/copper relay catalysis

Electrocatalytic dehydrogenative C(sp3)–H/C(sp)–H cross-coupling of tetrahydroisoquinolines with terminal alkynes has been achieved in a continuous-flow microreactor through 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)/copper relay catalysis. The reaction is easily scalable and requires low concentration of supporting electrolyte and no external chemical oxidants or ligands, providing straightforward and sustainable access to 2-functionalized tetrahydroisoquinolines.

Mixing control in a continuous-flow microreactor using electro-osmotic flow

In recent years, the gradual minimization of continuous-flow chemical reactors, which is stimulated by the interests of pharmaceutical production, has led to the emergence of a new generation of microreactors. A decrease in the thickness of the channels where the species contact and react, forces to search for new, non-mechanical, mechanisms for mixing the initial solutions. In this work, we consider the efficiency of mixing the reactants induced by electro-osmotic flow in a Hele-Shaw configuration with non-uniform zeta potential distribution. We consider the neutralization reaction, which has simple but non-linear kinetics, as a test reaction. The reaction occurs between two miscible solutions, which are initially separated in space and come into contact in a continuous-flow microreactor. The reaction proceeds frontally, which prevents the efficient mixing of the reactants due to diffusion. We show numerically that the mixing of solutions can be effectively controlled by specifying special forms of the zeta potential, which make it possible to lengthen the reaction front by an order of magnitude and increase the yield of the reaction product by several times.