Synthesis of new thiazolidine and imidazolidine derivatives of pharmacological interest

The hitherto unknown 5‐(2‐aryl‐2‐oxoethyl)‐4‐oxo‐1,3‐thiazolidines 1a‐l have been synthesized viacycloaddition process between thiourea and/or its derivatives with 3‐aroylpropenoic acids. ¹H NMR spectra revealed the presence of 1a‐c as a tautmeric mixture. The presence of the thiazoline tautmers (1a‐c) ′ was confirmed by methylating the tautmeric mixture, to the respective methylated derivatives 2‐N‐methylanilino‐5‐(2‐aryl‐2‐oxoethyl)‐4‐oxo‐1,3‐thiazolines 2a‐c and 1g‐i . Acidic treatment of 1 provided the respective 2‐oxo homologues 3a‐i . When 1a‐d , k were refluxed with DMF, molecular rearrangement was achieved, providing the 4‐oxo‐2‐thioxoimidazolidine isomers 4a‐d , k . Bromination of 4a and 4d in hot acetic acid afforded the respective (E,Z)‐5‐benzoylmethylene derivatives 5a,d which were prepared authentically. Thiation of 1a‐c and 4a‐c gave 5‐aryl‐2,3‐dihydro‐2‐phenyliminothieno2,3‐d]thiazoles 6a‐c and 1‐phenyl‐5‐aryl‐2,3‐dihydro‐2‐thioxothieno2,3‐d]imidazoles 7a‐c , respectively. The proposed structures have been confirmed by elemental analysis and spectroscopic data. The selected products showed different antimicrobial effect.