Ketene S,N-Acetals as Synthetic Intermediates for Heterocycles. Reaction of Ketene S,N-Acetals with 1,4-Quinones.

Annelation of ketene S,N-acetals with 1,4-quinones is found to give benzo[b]- and naphtho[1,2-b]furans bearing enamine groups. Subsequent enamine reaction allows the formation of 1-benz- and naphtho[1,2-b]oxepines and benzofuran-2-ones.