Advancements in synthesis of pharmacologically active imidazolidin‐4‐ones and stereochemistry of their Reactions with some Reagents

1‐Aryl, 1,3‐diaryl‐ and 5‐(2‐oxo‐2‐arylethyl)‐2‐thioxo‐imidazolidin‐4‐ones 2 were prepared as before, nevertheless, equivalent amounts of potassium hydroxide were added to the reaction conditions. This change, dramatically, reduced the reaction time and highly increased the yield of some derivatives. Treatment of 2 with sulfuric acid converted them into their analogous (E)/(E,Z)‐5‐(2‐oxo‐2‐arylethylidene) derivatives 3. Reactions of 2 and/or 3 with chromium trioxide affected their conversion into the corresponding 2,4‐diones 4 and 5, respectively. Treatment of 2 and/or 3 with ethyl bromoacetate affected conversion of the former into their respective 2,4‐diones 4, whereas it gave the respective 2‐alkylthio derivatives of the latter. Reactions of 2b with aromatic aldehydes gave mixtures of spiro‐1H‐ and 2H‐pyrrole diastereomers. Structures of the new products were evidenced by infrared, EI‐MS, 1H‐ and 13C‐NMR spectroscopic measurements. Many of the selected compounds showed good antimicrobial activity.