3,3a-Dihydrocyclopenta[b]chromen-1(2H)-ones from the reaction of salicylaldehyde and 2-cyclopenten-1-one.

The two title chromene compounds, 3,3a-dihydrocyclopenta[b]chromen-1(2H)-one, C16H12O2, (I), and 2-(2-hydroxybenzylidene)-3,3a-dihydrocyclopenta[b]chromen-1(2H)-one, C19H14O3, (II), have been determined in the monoclinic space group P2(1)/n. Compound (I) is mainly stabilized by C-H...pi interactions. Compound (II) is linked into infinite one-dimensional chains with a C(3) motif via intermolecular O-H...O hydrogen bonds. The intermolecular C-H...pi and pi-pi interactions also play key roles in stabilizing the crystal packing. Two intramolecular C-H...O hydrogen bonds with S(5) motifs were detected in (II).