Site‐Selective Oxidative C4 Alkenylation of (NH)‐Pyrroles Bearing an Electron‐Withdrawing C2 Group

Abstract

Abstract A regioselective method for the oxidative C−H alkenylation of free (NH)‐pyrroles with various activated and unactivated alkenes to afford 4‐alkenylated (NH)‐pyrroles in good to excellent yields was explored. The key features that distinguish this method from those reported in the current literature include: 1) The first report of the oxidative C4 alkenylation of (NH)‐pyrroles, 2) utilization of neutral conditions, 3) C2‐substituent‐controlled oxidative C4 alkenylation irrespective of the nature of the free (NH)‐pyrroles or N‐protected pyrroles used, 4) scope of using both electron‐deficient mono‐ and disubstituted alkenes and styrenes, and 5) synthesis of novel, enantiomerically pure 4‐alkenyl‐α‐methyl‐ N ‐benzylpyrroles bearing a stereocenter. An important application of this process to the synthesis of indoles through tandem C4/C5 double alkenylation followed by electrothermal cyclization was also examined.