New macrocyclic products containing four pyrido[2,1-b][1,3,5]thiadiazine units linked by methylene bridges and phenylene spacers were synthesized by reaction of morpholinium 3-cyano-4-methyl-6-oxo-1,6-dihydropyridine-2-thiolate with aromatic diamines (p-phenylenediamine, benzidine) and excess of HCHO. A rapid solvent-free procedure for synthesis of the starting thiolate was proposed. The structure of the products was confirmed by IR-, solid state NMR C-13 data and elemental analysis.