A CONVENIENT SYNTHESIS OF DIHYDRO-1,2,4-TRIAZOLO[3,2-B]QUINAZOLIN-9(1H)-ONES AND THEIR 1,2,4-TRIAZOLO DERIVATIVES

A range of dihydro-1,2,4-triazolo[3,2-b]quinazolin-9(1H)-ones (3) has been synthesized in very good yields by the reaction of 3-amino-2-anil ino-4(3H)-quinazolinone (1) with aromatics aldehydes in the presence o f excess piperidine as a base. The 1,2,4-triazolo[3,2-b]quinazolin-9(1 H)-ones could be obtained in very good yields by dehydrogenation of co mpounds 3 with thionyl chloride. Reaction of 1 with active methylene c ompounds (diethyl malonate and acetylacetone) resulted in the producti on of condensed products. These condensed products could be cyclized t o 1,2,4-triazolo[3,2-b]quinazolin-9(1H)-one by heating above the melti ng point. Acetylation of 1 by acetic anhydride was found to be depende nt on the reaction conditions. The acetyl derivative 3-acetamido-2-ani lino-4(3H)-quinazolinone formed under mild conditions, while dimerizat ion took place under strong conditions to give a pentacyclic compound in very good yield.