2-Phenylchroman-4-one as Synthone in Synthesis of New Five and Six Membered Rings Heterocyclic Compounds

Abstract

Chroman-4-one derivatives 1(a-i) were prepared by Pechman condensation of phenol or its substitutions with cinnamic acid by using polyphosphoric acid. These derivatives were reacted with hydrazine hydrate in refluxing ethanol to yield pyrazoline derivatives (2). The utility

3‐Arylidene‐4‐Chromanones and 3‐Arylidene‐4‐Thiochromanones: Versatile Synthons towards the Synthesis of Complex Heterocycles

“…The alternative structure 43 would not be expected to show downfield shift of such a magnitude. Raoof et al (2011) reported the synthesis of a few five membered (pyrazoles) and six membered heterocycles (pyrimidin-2-ones) from 3-arylidene-4-flavanones. [46] Heating a solution of (Z)-3-arylideneflavanones 22 in presence of urea in EtOH afforded the 4-(2-chlorophenyl)-5-phenyl-3,4,4a,5-substitutedchromano-[4,3-d] pyrimidin-2-ones 44 in low yields (Scheme 13).…”

“…Raoof et al (2011) reported the synthesis of a few five membered (pyrazoles) and six membered heterocycles (pyrimidin-2-ones) from 3-arylidene-4-flavanones. [46] Heating a solution of (Z)-3-arylideneflavanones 22 in presence of urea in EtOH afforded the 4-(2-chlorophenyl)-5-phenyl-3,4,4a,5-substitutedchromano-[4,3-d] pyrimidin-2-ones 44 in low yields (Scheme 13). Although the structure of the pyrimidines 44 (with three consecutive chiral centres) was assigned by UV, IR and NMR spectral studies, but the relative stereochemistry is not described.…”