Reactions of uracils, 2.3. Subsequent reactions of 7-ethoxypyrimido[4,5-d]pyrimidines: Nucleophilic exchange, pyrimido[4,5 : 4 ',5 ']pyrimido[1,2-a]quinazolines, benzo[f]pyrimido[4,5 : 4 ',5 '] pyrimido[1,2-d][1,3,4]triazepine

The nucleophilic substitution of 7-ethoxypyrimido[4,5-d]pyrimidines <(1a-d) under bar> is described to afford with ammonia 7-amino derivative a, with g lycine eater a, and with (+/-)2-phenylethylamine <(4a)under bar>, while rea ction with amino acid ester hydrochlorides in DMSO at 150 degrees C leads w ith remarkable ease to syn-elimination of ethylene to give tetraones <(5a.b )under bar>. DBN employed as base reacts with substitution and cleavage to pyrrolidinone-N-propylamino derivative (6) under bar, Pyridopyrimidines <(1 a-c)under bar> and hydrazine hydrate afford the 7-hydrazino derivatives <(7 a-c)under bar> which give with S,S-ketene acetal (8) under bar the 7-(N-1'- pyrazolyl)-derivatives <(9a-c)under bar>. The 6-(2'-methoxycarbonylphenyl)- derivative Id reacts with ammonia to the pyrimido-pyrimido carboxylate 6-am monium betaine <(10a)under bar>, and is converted into the tetracyclic pyri mido-pyrimido-quinazoline <(10b)under bar> by refluxing in DMSO. Short trea tment of Id with hydrazine gives 6-aminoquinazoline <(11)under bar> as a pu re product, while a prolonged heating leads to a nearly insoluble mixture o f <(11)under bar> and its isomer the 1,3,4-triazepine <(12)under bar> as th e main products and a third component in small amount, the structure of whi ch could not be elucidated till now.