6-Methyl-3-phenylthiochroman-4-one and 6-methoxy-3-phenylthiochroman-4-one: Configurational preference of the phenylthio group at the third position due to remote substitution

The pyran ring adopts a distorted sofa conformation in the title compounds, 6-methyl-3-phenylthiochroman-4-one (C16H14O2S), (I), and 6-methoxy-3-phenylthiochroman-4-one (C16H14O3S), (II). The S atom substituted at the third position is attached equatorially in (II) and axially in (I). High-resolution proton NMR studies could not provide a conclusive explanation for this feature.