Diels-Alder reactions of three fused nitrogen-containing bicyclic enones: an efficient method toward novel nitrogen-containing angular tricyclic skeletons.

The syntheses of three fused bicyclic enones, including 1,2,6,6a-tetrahydro-1-tosyl-cyclopenta[b]pyrrol-3(5H)-one, 1,2,3,6,7,7a-hexahydro-4H-1-tosyl-cyclopenta[b]pyridin-4-one and 1,2,5,6,7,7a-hexahydro-3H-1-tosyl-indol-3-one, via anionic cyclization and Diels-Alder reactions with various dienes to construct novel nitrogen-containing angular tricyclic skeletons are described.