Synthesis and Reactions of Some New Thiobarbituric Acid Derivatives

A series of novel thiobarbituric acid derivatives 3a–c , 5, and 12 were synthesized via the reaction of 4-benzoyl-1-cyanoacetylthiosemicarbazide ( 1 ) or its derivatives 2a–c , 9 with malonic acid and acetyl chloride. Coupling of thiobarbituric acid derivatives 3a-c and 5 with aromatic diazonium chlorides furnished a new series of the corresponding bisarylhydrazo-thiobarbituric dyes 4a–c . The reaction of 5 with cyclohexanone and sulfur under Gewald reaction condition afforded thieno[2,3-d]pyrimidine derivative 21 , that condensed with p-anisladehyde to give 5-arylidene thiobarbituric acid derivative 22 . The reaction of 1 with phenyl isothiocyanate afforded the non-isolable adduct 23 which was used as a key intermediate for the synthesis of polyfunctionally substituted thiazolidinone and thiobarbituric ring systems.