Organic synthesis in soft wall-free microreactors: real-time monitoring of fluorogenic reactions.

A new approach of "laboratory on a chip" (LOC) devoted to organic synthesis based on electrically operated ionic liquid microdroplets used as air-stable "soft" microreactors was recently introduced. A number of challenging issues have yet to be addressed to allow standard macroscale organic chemistry to be directly transposed in these nonclassical microreactors. In particular, since standard (i.e., magnetical or mechanical) stirring methods are prohibited in such wall-free microreactors, effective alternatives have to be developed to circumvent mass-transfer limitations. With this aim in mind, a fluorogenic version of a click chemistry reaction was developed to evaluate the efficiency of alternative mixing methods on the reaction kinetics. We demonstrate that the combination of chaotic advection created by surface acoustic waves combined with a temperature increase (Marangoni effect) leads to the same kinetics regime as in standard macroscale conditions. This opens the route for application of the new generation of LOC to efficient organic synthesis in microscale.