Synthesis and Characterization of Macrocyclic Polyaza(2,5)pyridinophanes Possessing Vitamin B6 Functionality

Abstract

Abstract Series of macrocyclic polyaza[m](2,5)pyridinophanes (poly=tri, tetra, penta; m=9, 12, 15)(8–10) and polyaza[m]paracyclophanes (11–13) were synthesized in excellent yields by the reaction of dichloropyridoxine derivatives (4) and α,α′-dibromo-p-xylene (5), respectively, with a series of 1,2-ethanediamine derivatives (1–3). These phanes were characterized on the basis of 1H NMR spectra. The methyl group at C6 of the pyridoxine moiety (a-series) revealed restricted rotation for all bridge sizes (m=9–15). In 8–10 without the methyl group (b-series), m=12 was the boundary between restricted and free rotation. In series 11–13, only 11 (m=9) showed restricted rotation. Atomic group equivalence was discussed in terms of boundary restricted rotation and an empirical rule for the prediction of the relationship between the bridge size and restricted rotation was proposed.