Synthesis of fused dihydropyrimidinones from cyclic-1,3-dicarbonyl compounds:Modified Biginelli syntehsis of 1,2,3,4,5,6,7,8-octahydroquinazolinediones and 3,4-dihydro-1H-indeno[1,2-d]pyrimidien-2,5-diones

摘要

Syntheses of bicyclo-3,4-dihydropyrimidinediones form cyclic 1,3-diketones such as 5,5-dimethyl-1,3-cyclohexanedione (Dimedone) and 1,3-indanedione have been attempted.During the multicomponent coupling of dimedone with (thio)urea and aldehydes,the unprecedented products of 9-aryl xnthene derivatives areobtained instead of the expected 4-aryl-1,2,3,4,5,6,7,8-octahydroquinazolinediones.Also,this reaction is senstive to solvent and the mole rtion of the ingredients used.High yields of bicyclic and tricyclic DHPMs with good selectivity are obtained using excess of urea and 1,3-dicarbonyl compounds.Interestingly,DHPMs are also formed in good to excellen tyields by neat stirring of 1,3-dicarbonyl compounds,aldehydes and urea,keeping oil-bath temperature at 110 degC.The mehcanistic aspects of the reaction are also mentioned.