ABSTRACT
The title compounds, C15H14N2OS (1a), C16H16N2OS (1b), and C17H18N2OS (1c), form a homologous series in which the size of the saturated ring increases from six- to eight-membered (with four, five and six methyl-ene groups respectively). For 1b and 1c, the central (CH2) n moieties are all displaced to the same side of their ring, and the CH2-CH2-CH2 angles are much wider than the standard sp 3 value; a database search indicates that these are general features of such ring systems. For 1a, the thio-phene ring lies with the sulfur atom on the opposite side of the Cthio-phene-Cpyridine bond to the cyano group, in contrast to 1b and 1c. For each compound, the packing may be described in terms of two 'weak' C-Hâ¯N hydrogen bonds, which link the mol-ecules to form one-dimensional (1a, 1c) or three-dimensional (1b) assemblies.
