A review of the syntheses of flavanones, thioflavanones, and azaflavanones from 2'‐substituted chalcones

Abstract Flavanones have been prepared by the cyclization of 2'‐hydroxychalcones using acidic reagents, such as H 2 SO 4 , HX, CF 3 COOH, CH H, KF‐celite, or SiO . Treatment with bases, LiOH, KOH, NaOAc, K CO pyridine, Et N, N ‐methylimidazole afforded flavanones. The conversion to flavanones has conducted Co(salpr), Fe(CN) 6 CuO, Ni(Tfacac) Thioflavanones deprotecting and cyclizing S ‐protected chalcones AgNO HBr, NaOH adding NaSH KCS OEt 2'‐halochalcones subsequent substitution. Azaflavanones 2'‐aminochalcones PO HCl, silica chloride, K‐10 clay. Furthermore, treatment Lewis acids, ZnCl SbCl Yb(OTf) InCl TaBr 5 CeCl azaflavanones, chiral azaflavanones were in presence per‐6‐ABCD, amine, BINOL‐phosphoric acid, thiourea catalyst.