Crystal structure of rac -(3a' R ,9a' R )-3a'-(indol-3-yl)-1′,2′,3′,3a',4′,9a'-hexahydrospiro[cyclopentane-1,9′-pentaleno[1,2- b ]indole] p -xylene hemisolvate

The title compound, C 26 H 26 N 2 ·0.5C 8 H 10 , is the first reported characterized 2:2 product from acid-catalyzed condensation of indole with cyclopentanone and no other 2:2 products were observed. Recrystallization from p -xylene gave the title hemisolvate with the p -xylene molecule located about an inversion center. The terminal pentalene ring is envelope-flap disordered at the C atom farthest from the skeletal indole unit, with a refined occupancy ratio of 0.819 (4):0.181 (4). The major component has this C atom bent away from the spiro -fused cyclopentane ring. In the crystal, molecules are connected by N—H...π interactions, forming chains along [100], and N—H...π and C—H...π interactions, forming chains along [001], which results in the formation of slabs parallel to (010).