Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• imines; asymmetric organocatalysis; cyclization; N-heterocycles; inverse electron demand aza-Diels–Alder reaction; Introduction Nitrogen-containing heterocycles are abundant scaffolds present in natural products, biologically active compounds, pharmaceuticals, synthetic agrochemicals, and functional

• furnish the cycloaddition product 13a. In 2019, Xu’s group published a bifunctional squaramide-catalyzed inverse electron demand aza-Diels–Alder reaction of saccharin-derived 1-azadienes 14 and azlactones 15 [27]. This methodology enables chiral tricyclic derivatives 16 bearing a quaternary amino acid

• and enantioselectivities. Later in 2021, Fernández-Salas, Alemán and co-workers developed a bifunctional squaramide-catalyzed enantioselective inverse electron demand aza-Diels–Alder reaction (IEDADA) between benzofuran-derived azadienes and silyl (di)enol ethers [33]. This work provides a useful