Structure and properties of macrocyclic compounds containing a pyrimidine fragment

The structure of a series of macrocyclic compounds consisting of a pyrimidine or 1,3,5-triazine ring and an aza-or thiapolymethylene bridge connecting the N¹ and N³ atoms of the heteroring is discussed. Some macroheterocycles undergo methylation at the sulfur atom by the action of methyl p-toluenesulfonate. The length of the polymethylene bridge determines conformation of the macroring. Compounds with a shorter bridge both in crystal and in solution are characterized by closely located structural fragments, while extension of the polymethylene chain gives rise to an unfolded structure. Conformational changes in solution are promoted by protonation of the bridging nitrogen atom, and deprotonation restores the initial structure of the macroring. The basicity of the bridging nitrogen atom depends on the geometric parameters of the macroring.