Synthesis of chalcones and derivatives

Abstract

In the present study, we undertook the total synthesis of several chalcones and derivatives namely chalcone, 2’-hydroxychalcone, 2’,4-dihydroxychalcone, 2’- hydroxy -3,4-dimethoxychalcone, 1,3-diphenylprop-2-en-1-ol, 2,3-dibromochalcone, 1-(1,3-diphenylallylidene)-1-phenylhidrazine, 3-hydroxy-2-phenyl-4-chromen-4-one and 2-phenylchromen-4-one. These target compounds were synthesized via Claisen- Schmidt condensation of the respective ketones and benzaldehydes under basic condition to give the corresponding chalcone, 2’-hydroxychalcone, and 2’-hydroxy - 3,4-dimethoxychalcone. At the same time, 2’,4-dihydroxychalcone was synthesized by Boron-trifluoride etherate method. 2’-Hydroxychalcone was converted to flavone by treatment with iodine in dimethylsulfoxide and to 3-hydroxy-2-phenyl-4- chromen-4-one by treating with hydrogen peroxide and NaOH. 1,3-Diphenylprop-2- en-1-ol was synthesized from chalcone through reduction process using NaBH4 while 1-(1,3-diphenylallylidene)-1-phenylhidrazine was prepared from chalcone and phenylhydrazine in ethanol. Structures were confirmed spectroscopically by IR, NMR (1H and 13C), DEPT and GC-MS. The antibacterial and toxicity activities of the synthesized compounds were evaluated by disc diffusion method and brine shrimps lethality test, respectively. All the synthesized compounds were inactive towards the tested bacteria. Chalcone and 2’-hydroxychalcone were found to be the most toxic compounds against brine shrimp (Artemia salina) both with LD50 1.7 ppm.