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.