N-alkylation of nitriles—III: Heterocyclizations by aminolysis of nitrilium salts: Imidazoles,4-oxoquinazolines and 4-quinolones

Several heterocyclizations have been carried out by aminolysis of nitrilium salts with aminoesters or propargyl amine. The aminolysis with norvaline methyl ester gave a 5-hydroxyimidazole derivative 8. With a β-aminoester such as methyl anthranilate, the amidinoesters 10 first obtained cyclized to 4-oxo-quinazolines 11. With a N-t-butyl substituted amidine ester 13, the ring closure occurred on the carbon α to the amidine giving a 2-amino-4-quinolone 14. It is only by refluxing in a strong base such as potassium t-butanolate in t-butunol that the oxoquinazoline 15 is obtained. Another type of ring closure occurred when the nitrilium salt was treated with propargylamine: the propargylamidine 16 formed was converted during the working up in the imidazole derivative 17.