SYNTHESES, PROPERTIES, AND PHOTOELECTRON-SPECTRA OF SUBSTITUTED AND LAYERED [2.2](2,6)PYRIDINOPARACYCLOPHANES

Syntheses of methyl-substituted [2.2](2, 6)pyridinoparacyclophanes 15, 16, and 17, as well as their corresponding 1, 9-dienes, 19, 20, and 21, are reported. The triple-layered [2.2](2, 6)pyridinoparacyclophanes 23, 24, and 30 have also been prepared. The temperature-dependent NMR behavior of the simple [2.2](2, 6)pyridinoparacyclophanes is in accord with a geometry where the pyridine ring is more or less parallel to the benzene ring, but undergoing rapid conformational flipping with an energy barrier of about 12 kcal/mol. The triple-layered cyclophane 30 shows a similar behavior, but with a slightly smaller energy barrier (11 kcal/mol). However, the apparent geometry of the corresponding 1, 9-dienes has the pyridine ring essentially perpendicular to the benzene ring. This is true also of the triple-layered cyclophane 23, where both pyridine rings are almost perpendicular to the central benzene ring. The [2.2](2, 6)pyridinoparacyclophanes show enhanced basicity compared to simple model pyridine derivatives, whereas their 1, 9-diene analogues show greatly reduced basicity. Photoelectron spectra have been measured for a number of the [2.2](2, 6)pyridinoparacyclophanes and their corresponding 1, 9-dienes and orbital assignments have been proposed for their lower energy ionization potentials. © 1979, American Chemical Society. All rights reserved.