Crystal structures of three homologues with increasing ring size: 2-methoxy-4-(thiophen-2-yl)-5,6,7,8-tetrahydroquinoline-3-carbonitrile, 2-methoxy-4-(thiophen-2-yl)-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine-3-carbonitrile and 2-methoxy-4-(thiophen-2-yl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile

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 methylene 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 sp3 value; a database search indicates that these are general features of such ring systems. For 1a, the thiophene ring lies with the sulfur atom on the opposite side of the Cthiophene — 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 — H...N hydrogen bonds, which link the molecules to form one-dimensional (1a, 1c) or three-dimensional (1b) assemblies.
Source: Acta Crystallographica Section E - Category: Chemistry Authors: Tags: crystal structure pyridine thiophene nitrile hydrogen bond research communications Source Type: research