Diastereo- and Enantioselective Synthesis of Eight-Membered N-Heterocycles from Benzofuran-Derived Azadienes and Ynones

Abstract

Enantioselective synthesis of eight-membered Nheterocycles represents a long-standing challenge in organic synthesis. Here, by combining the squaramide and DBU catalysis, a sequential asymmetric conjugate addition/cyclization reaction between benzofuran-derived azadienes and ynones has been well-developed, providing straightforward access to chiral eight-membered Nheterocycles in high yields with stereoselectivities. This protocol features the use of a bifunctional squaramide catalyst for controlling the enantioselectivity of products, while the DBU is utilized to achieve intramolecular cyclization and improve the diastereoselectivity of products.