Synthesis of new thiazolidine and imidazolidine derivatives of pharmacological interest

The hitherto unknown 5-(2-aryl-2-oxoethyl)-4-oxo-1,3-thiazolidines 1a-1 have been synthesized via cycloaddition process between thiourea and/or its derivatives with 3-aroylpropenoic acids. H-1 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-phenyliminothieno[2,3-d]thiazoles 6a-c and 1-phenyl-5-aryl-2,3-dihydro-2-thioxothieno[2,3-d]imidazoles 7a-c, respectively. The proposed structures have been confirmed by elemental analysis and spectroscopic data. The selected products showed different antimicrobial effect.