Electrochemical [3+2]/[4+2] cyclization to indole-fused polycyclics

Abstract

The preparation of highly complex indole-fused polycyclics have been in high demand because of their abundant biological activities. The electrochemical coupling of the radical intermediates with adjacent indole rings has been recognized as a green, straightforward and powerful methodology in the construction of the compounds above because it is highlighted by high atom and step economy under mild and exogenous oxidants free conditions. However, it is challenging and undeveloped because of the low oxidation potential of indole rings, which makes it easy to decompose under electrolysis conditions. Herein, we reported a straightforward electrosynthesis of indole-fused polycyclics through radical domino couplings between N-methacryloylindoles and α-allyl activated methylenes. This electrolysis had been proved to be efficient in the open air with good functional group tolerance, which meant stringent removal of H2O and oxygen was not necessary.