Structural investigations of 1,2,3,4-tetrahydrocarbazole derivatives. I. 2,3-Dihydro-9-(phenylsulfonyl)carbazole-4(1H)-one and 1,2,3,4-tetrahydrocarbazole-1-spiro-2'-[1,3]dithiolane

Rings A and B of the title compounds, C 18 H 15 NO 3 S (1) and C 14 H 15 NS 2 (2), are planar while the hydrogenated C rings are not. The rings in the tetrahydrocarbazole skeleton are twisted with respect to each other