NBS-Enabled Rapid Cyclization of Dipyrroethenes to Access meso-Tetraaryl Porphycenes

We introduce the concept of N-bromo succinimide (NBS) mediated rapid macrocyclization of 5,6-diaryl dipyrroethenes (DPE) to access meso-tetraaryl porphycenes in second’s time frame. This fastest strategy of porphycene synthesis not only eliminates the requirements of reactive p-TSA, sacrificial oxidant, and sophisticated techniques associated with the previous methods but also enables the reaction under ‘open air’ with significantly improved reaction yields up to 76%, while minimizing the other biproducts. Moreover, this protocol is well compatible with six and five membered aryl substituents at meso-positions and verified up to gram scale synthesis of meso-tetratolyl porphycene. Combined experimental and computational studies highlight that the NBS-mediated umpolung modification of the DPE core is the key step in driving the reaction in the forward direction with such exclusive selec-tivity and yield in a short span of time.