Synthesis of 8-membered Tetrahydroazocines via Manganese-Mediated Regioselective Sulfonylation/Cyclization of N-Substituted Enamides with Sodium Sulfinites

Abstract

Intermolecular radical cascade cyclization of tethered alkynes involving the cracking of aryl or vinyl C(sp2)–H has become an important pathway for the synthesis of benzene-fused or C=C bond-containing heterocyclic building blocks. While the major progress has been made in the construction of 5-7-membered heterocycles, the construction of 8-membered heterocycles such as tetrahydroazocines has proven elusive and challenge. Herein, we report the manganese-mediated sulfonylation/cyclization of N-substituted enamides to synthesize 8-membered tetrahydroazocines, involving chemoselective sulfonyl radical addition to the C–C triple bond and 8-endo-trig cyclization