Crystal structures and conformations of two Diels–Alder adduct derivatives: 1,8-bis­(thio­phen-2-yl)-14-oxa­tetra­cyclo­[6.5.1.0(2,7).0(9,13)]tetra­deca-2(7),3,5-trien-10-one and 1,8-diphenyl-14-oxa­tetra­cyclo[6.5.1.0(2,7).0(9,13)] tetra­deca-2,4,6-trien-10-one

The title compounds, C(21)H(16)O(2)S(2) (I) and C(25)H(20)O(2) (II), are products of a tandem ‘pincer’ Diels–Alder reaction consisting of [2 + 2] cyclo­additions between benzo[c]furan and cyclo­penta­none. Each comprises a fused tetra­cyclic ring system containing two five-membered rings (in envelope conformations with the O atom as the flap) and six-membered rings (in boat conformations). In addition, two thio­phene rings in (I) and two phenyl rings in (II) are attached to the tetra­cyclic ring system. The cyclo­penta­none ring adopts a twisted conformation in (I) and an envelope conformation in (II). In (I), the thio­phene rings are positionally disordered over two sets of sites, with occupancy ratios of 0.901 (2):0.099 (2) and 0.666 (2):0.334 (2). In (II), the oxygen atom of the cyclo­penta­none ring is rotationally disordered over two sites with an occupancy ratio of 0.579 (4):0.421 (4). The mol­ecular structure of (I) is stabilized by an intra­molecular C—H⋯O hydrogen bond, which generates an S(7) ring motif. In the crystal, the mol­ecules are linked via weak C—H⋯O hydrogen bonds, which generate R (2) (2)(16) ring motifs in (I) and C(8) chains in (II). In both structures, the crystal packing also features C—H⋯π inter­actions. The crystal studied of compound (I) was twinned by non-merohedry. The twin component is related by the twin law [−1 0 0 −0.101 1 −0.484 0 0 −1] operated by a twofold rotation axis parallel to the b axis. The structure of (I) was refined with a twin scale factor of 0.275 (2).