Design, synthesis and spectral characterization of cyclotriphosphazenes including heterocyclic rings

In this study, described the synthesis on a cyclotriphosphazene containing the spirocyclic 2,2′-dioxybiphenyl group and 2-mercapto-1-methylimidazole (methimazole) or 2-mercaptothiazoline (MTZ) moieties. These spiro(in difunctional ligands, both ends are bound to the same phosphorus) cyclotriphosphazene derivatives (6, 7a) were synthesized in two steps. In first step; mono substituted phosphazene compounds 2,4,4,6,6-pentachloro-2-(2-mercapto-1-methylimidazolyl) cyclo2λ⁵, 4λ⁵, 6λ⁵, triphosphazatriene; N₄P₃Cl₅C₃S₂H₅ (4), and 2,4,4,6,6-pentachloro-2-(2-mercapto-tiyazolinyl) cyclo2λ⁵, 4λ⁵, 6λ⁵, triphosphazatriene; N₄P₃Cl₅C₄S₂H₄ (5)] were prepared from the reaction of hexachlorocyclotriphosphazatriene (trimer, N₃P₃Cl₆, 1), with methimazole (2) or MTZ (3) in tetrahydrofurane (THF) in the presence of metallic sodium under an argon atmosphere.

In second step; monospiro2-mercaptothiazolinyl (7a) and dispiro2-mercapto-1-methylimidazolyl sübstituted (6) phosphazene derivatives were obtained from the reactions of 4 and 5 with 2,2′-dihydroxybiphenyl (8) in acetone in the presence of potassium carbonate (K₂CO₃). Structural characterizations of all obtained compounds were made using by elemental analysis, FT-IR, ¹H, ¹³C and ³¹P NMR spectroscopies. Compounds 5–7a are reported for the first time in this study.