Small, Strained Cyclophanes with Methine Hydrogens Projected toward the Centers of Aromatic Rings

Article abstract of DOI:10.1021/ja00190a039

The syntheses of 2,8,17-trithia-in-<3^5,12><9>metacyclophane, 2,7,16-trithia-in-<3^5,11><8>metacyclophane, and 2,6,15-trithia-in-<3^4,10><7>metacyclophane are described.Due to the extreme proximity of the apical methine hydrogen atoms and the centers of the aromatic rings, the compounds display very high field 1H NMR resonances and very high frequency IR C-H stretching bands.X-ray crystallographic analyses of the latter two compounds reveal hydrogen-to-ring distances of only 1.81 and 1.69 Angstroem, respectively.The experimentally determined geometries are contrasted with structures generated by molecular mechanics and semiempirical molecular orbital calculations.