Fused azolium salts. 10. Selective ring openings of isomeric fused thiazolium salts with nucleophiles

Heterocycles with a bridging nitrogen atom. 19. Development of routes for the synthesis of oxazoloisoquinolinium salts based on phenacylation of α-methyl-1(3)-isoquinolones

“…Clevage of the C(2)-O bond under the action of sodium methylate was observed by us previously for oxazolopyridinium salt 1 (R = H) [22]. An analogous direction of opening the azole ring was also observed for the reaction of a thiazoloisoquinolinium salt (isostructure of salt 14) with a secondary amine [20].…”

“…(An example of a similar process is known, the synthesis of the thioanalog of system 3 by the acid cyclization of 3-(phenacylthio)isoquinoline [20]). Meanwhile, all attempts to close the oxazolium ring in O-phenacyl derivative 10 by the action of conc.…”

Synthesis of new tetrazolyldienylphenothiazines as potential multidrug resistance inhibitory compounds

“…In the course of our earlier results on fused azolium salts we elaborated a facile synthetic route to various azolyl dienamines [4][5][6][7] and we have found that the phenothiazine moiety also can be introduced into these compounds. 8 These derivatives can be obtained in a single step by ring opening of azolopyridinium salts (2) by secondary amines.…”