| Title |
Synthesis and characterization of new pyrano[2,3-c]pyrazole derivatives as 3-hydroxyflavone analogues / |
| Authors |
Urbonavičius, Arminas ; Krikštolaitytė, Sonata ; Bieliauskas, Aurimas ; Martynaitis, Vytas ; Solovjova, Joana ; Žukauskaitė, Asta ; Arbačiauskienė, Eglė ; Šačkus, Algirdas |
| DOI |
10.3390/molecules28186599 |
| Full Text |
|
| Is Part of |
Molecules.. Basel : MDPI. 2023, vol. 28, iss. 18, art. no. 6599, p. 1-26.. ISSN 1420-3049 |
| Keywords [eng] |
3-hydroxyflavone ; algar–flynn–oyamada reaction ; ESIPT ; NMR investigation ; pyrano[2,3-c]pyrazoles ; pyrazoles |
| Abstract [eng] |
In this paper, an efficient synthetic route from pyrazole-chalcones to novel 6-aryl-5-hydroxy-2-phenylpyrano[2,3-c]pyrazol-4(2H)-ones as 3-hydroxyflavone analogues is described. The methylation of 5-hydroxy-2,6-phenylpyrano[2,3-c]pyrazol-4(2H)-one with methyl iodide in the presence of a base yielded a compound containing a 5-methoxy group, while the analogous reaction of 5-hydroxy-2-phenyl-6-(pyridin-4-yl)pyrano[2,3-c]pyrazol-4(2H)-one led to the zwitterionic 6-(N-methylpyridinium)pyrano[2,3-c]pyrazol derivative. The treatment of 5-hydroxy-2,6-phenylpyrano[2,3-c]pyrazol-4(2H)-one with triflic anhydride afforded a 5-trifloylsubstituted compound, which was further used in carbon-carbon bond forming Pd-catalyzed coupling reactions to yield 5-(hetero)aryl- and 5-carbo-functionalized pyrano[2,3-c]pyrazoles. The excited-state intramolecular proton transfer (ESIPT) reaction of 5-hydroxypyrano[2,3-c]pyrazoles from the 5-hydroxy moiety to the carbonyl group in polar protic, polar aprotic, and nonpolar solvents was observed, resulting in well-resolved two-band fluorescence. The structures of the novel heterocyclic compounds were confirmed by 1H-, 13C-, 15N-, and 19F-NMR spectroscopy, HRMS, and single-crystal X-ray diffraction data. |
| Published |
Basel : MDPI |
| Type |
Journal article |
| Language |
English |
| Publication date |
2023 |
| CC license |
|
