Convenient and versatile method of 8-amino-6-(2-R-thiazol-4-yl)-1,7-naphthyridines synthesis

On the base of 3-formylpicolinic acid by two successive heterocyclizations (the formation of a pyrone fragment by the cyclization of chloroacetone with the carboxyl and formyl groups; and the construction of the thiazole cycle through the bromination of the acetyl fragment and following interaction with thioamides), 6-(2-(phenyl/thiophen-2-yl)thiazole-4-yl)-8H-pyrano[3,4-b]pyridin-8-ones were obtained; and then the pyrone fragment was converted to pyridone by the action of ammonia under high pressure. When such 6-(2-R-thiazol-4-yl)-1,7-naphthyridin-8(7H)-ones reacted with triflic anhydride, O-sulfonylation of the pyridone fragment occurred, after that triflate group was easily substituted by secondary cyclic aliphatic amines. Thus, a number of new 8-amino-6-(2-R-thiazol-4-yl)-1,7-naphthyridines – previously inaccessible heterocyclic derivatives with promising biological activity – were obtained.