The title compounds, C19H21F3O2S and C24H19F3OS, were prepared via chemo- and regioselective [3 + 2]-cyclo-additions of the respective thio-carbonyl ylides (thio-carbonyl S-methanides), generated in situ, with (E)-4,4,4-tri-fluoro-1-phenyl-but-2-en-1-one. The thio-phene ring in the crystal structure of each compound has an envelope conformation. The largest differences between the two mol-ecular structures is in the bond lengths about the quaternary C atom of the thio-phene ring; in the spiro-cyclic structure, the C-C bonds to the spiro C atom in the cyclo-butane ring are around 1.60 Å, although this is also observed in related structures. In the same structure, weak inter-molecular C-H⋯X (X = S, O) inter-actions link the mol-ecules into extended ribbons running parallel to the [001] direction. In the other structure, weak C-H⋯π inter-actions link the mol-ecules into sheets parallel to the (010) plane.
Keywords: [3 + 2]-cycloaddition; crystal structure; tetrahydrothiophene.