Novel CAL-B Catalyzed Synthetic Protocols for Pyridodipyrimidines and Mercapto Oxadiazoles

CAL-B catalyzed novel synthetic routes have been developed for getting better to excellent yields of the pyridodipyrimidines and mercapto oxadiazoles. Here, for the first time, one pot cyclo condensation of barbituric acid, aromatic aldehydes, and ammonium acetate has been carried at room temperature in dichloromethane in the presence of biocatalyst, CAL-B and obtained 5-aryl-9,10-dihydropyrido[2,3-d:6,5-d']dipyrimidine-2,4,6,8(1H,3H,5H,7H)-tetraones (3a-k). CAL-B catalyzed cyclo condensation of arylhydrazides and carbon disulphide has also been carried in ethanol for getting 5-(p-substituted phenyl)-1,3,4-oxadiazole-2-thiol (6a-b). Mercapto oxadiazoles (6a-b) are also separately allowed to react with substituted phenacyl bromides in the presence of trimethylamine and obtained 1-aryl-2-((5-substitutedphenyl-1,3,4-oxadiazol-2-yl)thio)ethanones (8a-h). The developed routes are efficient, clean, and cost-effective. Synthesized compounds; (3a-k), (6a-b), and (8a-h) are thoroughly characterized by their spectral data. CAL-B, catalyzed efficient one pot synthetic routes have been first time developed for getting better to excellent yields of the 5-aryl-9,10-dihydropyrido[2,3-d:6,5-d']dipyrimidine-2,4,6,8(1H,3H,5H,7H)-tetraones (3a-k) and 5-(p-substituted phenyl)-1,3,4-oxadiazole-2-thiol (6a-b).