Novel, Catalyst-free One-pot Multicomponent Synthesis of Pyrazolopyridopyrimidine-diones in Water Under Ultrasonic Condition

A novel catalyst-free route was utilised for the first time to achieve a synthesis of fourteen new 3-methyl-1,4,8,9-tetrahydro-5 H -pyrazolo[4,3:5,6]pyrido[2,3- d ]pyrimidine-5,7(6 H )-diones via a one-pot five-component reaction of substituted aromatic/hetero aromatic aldehydes, barbituric acid, ethyl acetoacetate, hydrazine hydrate and ammonium acetate in water under ultrasonication. The reaction conversion took place between 15 and 18 min, with the yield ranging from 85% to 98%; and it was found that five compounds gave <90% yield and nine compounds accorded yields >90%. The methodology is expeditious and furnishes varied advantages like shorter reaction time, energy efficiency, eco-sustainability and work under mild condition.