Synthesis of heterocyclic chalcones and their novel pyrazoline derivatives

Abstract

Chalcones are open-chain flavanoids possessing a basic scaffold of two aromatic rings linked by a three carbon α,β-unsaturated carbonyl system. Synthetic and naturally occurring chalcones display a wide range of biological activities such as antibacterial, anticancer and antioxidant activity because of their α,β-unsaturatedcarbonyl moiety. Modifications to their scaffold at the aromatic rings or the α,β-unsaturated carbonyl moiety have been found to either enhance or decrease the chalcones’ efficiency. Heterocyclic chalcones are chalcones produced by changing one or both of the aromatic rings to a heterocyclic core such as thiophene, furan,pyridine or pyrazine. Four heterocyclic chalcones and their N-acetylated pyrazolinederivatives have been synthesized with a thiophene scaffold as the base combined with pyridine, furan or pyrazine. The synthesis of the heterocyclic chalcones was carried out via the Claisen-Schmidt condensation reaction between the respective aldehydes and ketones with sodium hydroxide as the basic catalyst. The pyrazoline,oxazine, thiazine and pyrimidine derivatives of chalcones can be produced through the condensation of their α,β-unsaturated carbonyl moiety. The heterocyclic chalcones were refluxed with hydrazine hydrate and anhydrous sodium acetate in glacial acetic acid to obtain their N-acetylated pyrazoline derivatives. Structural characterization using ATR-FTIR, 1H NMR, 13C NMR and HMQC has confirmed their structures and the products were obtained with moderate yields.