A New Efficient Route to (±)-Physostigmine and (±)-Physovenine by Means of 5-exo Selective Aryl Radical Cyclization of o-Bromo-N-acryloylanilides

Bu3SnH-mediated aryl radical cyclization of o-bromo-N-acryloylanilides 16 and 17 proceeded in a 5-exo manner exclusively to give, in high yields, oxindoles 3 and 4, the key intermediates for the synthesis of (±)-physostigmine and (±)-physovenine, respectively.