Synthesis and NMR spectroscopy investigations of functionalized spiropyranochromenediones and their spirothiadiazole derivatives

Abstract

This investigation focuses on the synthesis of spiropyranoneoflavones and the modification of obtained compounds at the exocyclic oxygen atom. Kabbe cyclization of 6-acetyl-7‑hydroxy-8-methyl-4-phenyl-2H-chromene-2-one with cyclohexanone or cyclopentanone in the presence of pyrrolidine provided 10-methyl-4-phenyl-2H-spiro[cyclohexane(cyclopentane)-1’,8-pyrano[3,2-g]chromene]-2,6(7H)-diones. Their new functionalized derivatives with thiosemicarbazide residues were synthesized. Acetylation of obtained thiosemicarbazones with acetic anhydride proceeded via cyclization of thiosemicarbazide fragment into 1,3,4-thiadiazole ring to give corresponding N-[3'-acetyl-10-methyl-8-oxo-6-phenyl-3'H,8H-dispiro[cyclohexane-1,2’-pyrano[3,2-g]chromene-4,2'-[1,3,4]thiadiazol]-5'-yl]acetamide and N-[3'-acetyl-10-methyl-8-oxo-6-phenyl-3'H,8H-dispiro[cyclopentane-1,2’-pyrano[3,2-g]chromene-4,2'-[1,3,4]thiadiazol]-5'-yl]acetamide. The structure of the obtained compounds was confirmed by NMR spectroscopy