Et₃N‑Catalyzed Tandem Formal [4 + 3] Annulation/Decarboxylation/Isomerization of Methyl Coumalate with Imine Esters: Access to Functionalized Azepine Derivatives

An unprecedented catalytic tandem formal [4 + 3] cycloaddition/decarboxylation/isomerization of methyl coumalate and imine esters is successfully developed. This tandem reaction only requires Et₃N as the mild base affording a series of highly functionalized seven-membered heterocyclic azepine derivatives in good yields with excellent regioselectivities.