Exo Diels-Alder adducts between ortho- and para-N-acetoxyphenylmaleimides and furan.

In exo-2-(3,5-dioxo-10-oxa-4-azatricyclo[5.2.1.0(2,6)]dec-8-en-4-yl)phenyl acetate, C(16)H(13)NO(5), the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1) degrees ], in contrast with the smaller deviations found in the para isomer exo-4-(3,5-dioxo-10-oxa-4-azatricyclo[5.2.1.0(2,6)]dec-8-en-4-yl)phenyl acetate, C(16)H(13)NO(5), these being 63.6 (1) and 37.0 (1) degrees for the two crystallographically independent molecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C-H.X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane.