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.