Synthesis and Characterization of Novel Heterocyclic Chalcones from 1-Phenyl-1H-pyrazol-3-ol

Abstract

An efficient synthetic route to construct diverse pyrazole-based chalcones from 1-phenyl-1H-pyrazol-3-ols bearing a formyl or acetyl group on the C4 position of pyrazole ring, employing a base-catalysed Claisen–Schmidt condensation reaction, is described. Isomeric chalcones were further reacted with N-hydroxy-4-toluenesulfonamide and regioselective formation of 3,5-disubstituted 1,2-oxazoles was established. The novel pyrazole-chalcones and 1,2-oxazoles were characterized by an in-depth analysis of NMR spectral data, which were obtained through a combination of standard and advanced NMR spectroscopy techniques.

Synthesis and Characterization of New Pyrano[2,3-c]pyrazole Derivatives as 3-Hydroxyflavone Analogues

“…The synthesis of 6-(hetero)aryl-5-hydroxy-2-phenylpyrano[2,3- c ]pyrazol-4(2 H )-ones 3a – h was carried out as depicted in Scheme 1 . 1-Phenyl-1 H -pyrazol-3-ol 1 was obtained using a previously reported method [ 42 , 43 ] and subjected to a Claisen–Schmidt condensation reaction with variously 4′-substituted (hetero)aryl aldehydes in the presence of ethanolic sodium hydroxide, as we have described [ 44 ]. Heating the reaction mixture at 55 °C for 3 to 5 h afforded ( E )-1-(3-hydroxy-1-phenyl-1 H -pyrazol-4-yl)prop-2-en-1-ones 2a – h in poor to excellent yields (36–95%).…”

“…For example, the excitation of form N - 3a leads to the excited state N* , which passes into the product T* by means of proton transfer ( Figure 7 ). The T* form then relaxes to the ground state T form and emits fluorescence at a much longer wavelength compared to normal absorption [ 28 , 44 ]. Therefore, the form N* of the normal emission has a Stokes shift of 8927 cm −1 , while the tautomeric product T* has a Stokes shift of 12491 cm −1 .…”

“…Compounds 2a – c and 2e – h were synthesized in accordance with the procedure described in ref. [ 44 ].…”

Two Important Anticancer Mechanisms of Natural and Synthetic Chalcones

“…During the reaction, the base (catalyst) attacks α-hydrogen of acetophenone and forms an enolate anion (carbanion). The carbanion attacks the carbonyl group of benzaldehyde and forms a β-hydroxycarbonyl intermediate, from which chalcone is obtained [ 135 , 136 , 137 , 138 , 139 , 140 , 141 ].…”

Advances in the Synthesis of Heteroaromatic Hybrid Chalcones

“…has been investigated thoroughly over the years, with numerous research articles as well as several reviews appearing in the last decade describing the current chalcone synthetic strategies, the heterocycles derived from them, and the bioactivity and pharmaceutical uses of these compounds [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Within that context, the preparation of more highly functionalized chalcones that contain heteroaromatic components has been an area of intense research over the last decade [ 10 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”