Copper-Catalyzed [2 + 2] Cyclization/Ring Expansion of Ene-Ynamides: Construction of Medium- and Large-Sized Rings

Abstract

Catalytic cyclization of enynes is an efficient approach for the preparation of cyclic compounds, and a large variety of four-to six-membered rings could be synthesized using this method. However, it has been rarely employed for the construction of medium-and large-sized rings. Herein, we describe a copper-catalyzed cycloisomerization of ene-ynamides through a [2 + 2] cyclization/electrocyclic ring opening cascade, leading to the atom-economical assembly of indole-fused medium-and largesized rings in moderate to excellent yields under mild reaction conditions. Importantly, the synthetic utility of this reaction was demonstrated by the convenient synthesis of iprindole.Letter pubs.acs.org/OrgLett