X-ray crystallographic studies of four monosubstituted thienopyridines. Comparison of experimental data with calculated or measured values for the parent compounds

X-ray crystallographic data are reported for thieno[3,2-b]pyridine-2-carbon itrile (<(1b)under bar>), thieno[3,2-c]pyridine-4-carbonitrile (<(2b)under bar>), 3-acetylaminothieno[2,3-c]pyridine (<(3b)under bar>), and ethyl thie no[2,3-b]pyridine-3-carboxylate (<(4b)under bar>). All of the thienopyridin e ring systems are planar with internal bond angles of 90.7 +/- 0.6 degrees for C-S-C and 115.9 +/- 1.9 degrees for C-N-C. C-S and C-N bond lengths in the rings are 1.73 +/- 0.02 Angstrom and 1.34 +/- 0.02 Angstrom, respectiv ely. Comparison is made of our measured data with bond angles and lengths c alculated from molecular orbital theory for the parent unsubstituted compou nds <(1a)under bar>, <(2a)under bar> and <(4a)under bar> and for reported e xperimental data for parent <(3a)under bar>. In C-13 Nmr spectral data are general, numerical values are remarkably close in the corresponding (a) und er bar and (b) under bar systems. also reported for <(2b)under bar>-<(4b)un der bar>.