Conformations of three heterocyclic perhydropyrrolobenzofurans and polymeric assembly via co-operative intermolecular C-H...O hydrogen bonds.

In 1-cyclohexyl-6,6,8a-trimethyl-3a,6,7,8a-tetrahydro-1H-1-benzofuro[2,3-b]pyrrole-2,4(3H,5H)-dione, C19H27NO3, (I), and the isomorphous compounds 6,6,8a-trimethyl-1-phenyl-3a,6,7,8a-tetrahydro-1H-1-benzofuro[2,3-b]pyrrole-2,4(3H,5H)-dione, C19H21NO3, (II), and 6,6,8a-trimethyl-1-(3-pyridyl)-3a,6,7,8a-tetrahydro-1H-1-benzofuro[2,3-b]pyrrole-2,4(3H,5H)-dione, C18H20N2O3, (III), the tetrahydrobenzo-dihydrofuro-pyrrolidine ring systems are folded at the cis junction of the five-membered rings, giving rise to a non-planar shape of the tricyclic cores. The dihydrofuran and pyrrolidine rings in (I) are puckered and adopt an envelope conformation. The cyclohexene rings adopt a half-chair conformation in all the molecules, while the substituent N-cyclohexyl ring in (I) assumes a chair form. Short intramolecular C-H...O contacts form S(5) and S(6) motifs. The isomorphous compounds (II) and (III) are effectively isostructural, and aggregate into chains via intermolecular C-H...O hydrogen bonds.