Visible-Light-Driven CarboxyLic Amine Protocol (CLAP) for the Synthesis of 2-Substituted Piperazines under Batch and Flow Conditions.

Piperazines are privileged scaffolds in medicinal chemistry. Disclosed herein is a visible-light-promoted decarboxylative annulation protocol between a glycine-based diamine and various aldehydes to access 2-aryl, 2-heteroaryl, as well as 2-alkyl piperazines. The iridium-based complex [Ir(ppy)2(dtbpy)]PF6 and carbazolyl dicyanobenzene 4CzIPN were found to be the photocatalysts of choice to efficiently perform the transformation under mild conditions, whether in batch or in continuous mode.