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Abstract:
From the pyridinophanes 1 –4 (1) which consist of two nicotinic ester units in the four different orientations possible, by diquaternization the corresponding pyridiniophane diiodides 7 –10 were obtained. UV and 1H NMR spectra of these [2.2]paracyclophanes with two positive ring charges are discussed; the molecular structure of the diperchlorate derived from 7 was determined by X‐ray structure analysis. — By sodium dithionite reduction the pyridinium salt 5 with an analogous substitution pattern as 7 –10 was reduced to the corresponding 1,4‐dihydro compound 6 . 7 reacted with sodium dithionite, however, to the double 1,2‐dihydropyridine system 15 which yielded with maleic anhydride the 1:2‐adduct 16 . Access to the wanted series of semi‐reduced 1,4‐dihydro derivatives 11 –14 was obtained by the reaction with 6 as the reducing reagent. For 11 and 14 the UV/VIS and 1H NMR spectra are reported. From first spin saturation transfer 1H NMR experiments it is concluded that in 14 an intramolecular exchange of redox‐equivalents occurs whereas for the isomer 11 this is not observed under the same conditions.
