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

Solvent‐free, microwave‐assisted, solid‐catalyzed synthesis and α‐Glucosidase inhibition of chalcones

“…Conversion of 2′‐hydroxychalcone to flavanone can be predicted through the cyclization step in basic condition, which has been reported common in literature. [ 20 ]…”

“…Our observation is consistent with other results, in which the cyclization is possible under K10 clay as a solid acidic catalyst. [ 20 ] However, it was difficult to divine in detail when the cyclization only occurred in this case.…”

“…Conversion of 2′-hydroxychalcone to flavanone can be predicted through the cyclization step in basic condition, which has been reported common in literature. [20] Table 1 In order to synthesize 2′-hydroxychalcones, we performed the condensation reactions between 2hydroxyacetophenone and benzaldehydes, which catalyzed by clay under microwave irradiation. 2′-Hydroxychalcones (3l-3r) were successfully synthesized in yields from 43% to 61%.…”

Enantioselective Synthesis of Aza-Flavanones with an All-Carbon Quaternary Stereocenter via NHC-Catalyzed Intramolecular Annulation

“…These remarkable molecules are characterized by an aromatic ring fused to a six-membered heterocyclic system that incorporates a nitrogen atom. This unique configuration is frequently observed in a plethora of bioactive natural products, many of which exhibit a wide range of pharmacological activities and therapeutic potential . The designation of these specific structural frameworks as “privileged structures” in drug development reflects their exceptional ability to modulate various biological targets.…”

“…This unique configuration is frequently observed in a plethora of bioactive natural products, many of which exhibit a wide range of pharmacological activities and therapeutic potential. 1 The designation of these specific structural frameworks as “privileged structures” in drug development reflects their exceptional ability to modulate various biological targets. Their multifaceted nature has captured the attention of researchers in medicinal chemistry, leading to extensive studies on their structure–activity relationships (SAR) and potential applications in the treatment of various diseases.…”