Selectively building C=S bond of 3-aroylflavone into novel 3-aroyl-4-thioflavone scaffold via thionation by Lawesson’s reagent

Abstract

Lawesson’s reagent, a well-known thionating reagent, has been applied for the thionation of the 3-aroylflavones that contain two C=O groups. Selective thionation of one C=O group in the 3-aroylflavones to afford novel 3-aroyl-4-thioflavones has occurred preferably than conversion of two C=O groups. Twenty novel 3-aroyl-4-thioflavone derivatives were synthesized with isolated yields ranging from 50 to 96% within 15–90 min. Density functional theory (DFT) studies have been employed for further investigation on the reactivities, product stability, and the thermodynamic value of the thionation reaction of 3-aroylflavone with LR. The lower energy level of band gap obtained from the calculation of HOMO and LUMO energy levels combined with thermodynamic parameters and energy disparity are the main explanation for the less existence of 3-(phenylcarbonothioyl)-4-thioflavone. Furthermore, the FT–IR, ¹H-NMR, and ¹³C-NMR data of typical 3-aroylflavone and corresponding 3-aroyl-4-thioflavone have also been compared to find an interesting structural interpretation.

Graphical abstract