Cyclocondensation reactions of heterocyclic carbonyl compounds XI . Synthesis and study of cyclocondensation reactions of some 3‐substituted‐5‐(2‐aminobenzyl)‐1 H ‐[1,2,4]triazine‐6‐ones

A series of 2‐substituted‐4‐(2‐nitrobenzylidene)‐4,5‐dihydrooxazol‐5‐ones ( 2a‐2i ) was prepared by the Erlenmeyer's synthesis of 2‐nitrobenzaldehyde with acylglycines ( 1a‐1i ) and the series of corresponding aminoderivatives ( 3b‐3d and 3g‐3i ) was synthetised by catalytic hydrogenation of ( 2b‐2d and 3g‐3i ). Hydrazinolysis of azlactones ( 2 ) and ( 3 ) gave hydrazides ( 4 ) and ( 5 ). The hydrazides ( 5 ) were also obtained by catalytic hydrogenation of corresponding nitroderivatives ( 4 ). The cyclization reaction of hydrazides ( 4 ) or ( 5 ) proceeded to 3,5‐disubstituted‐1,6‐dihydro‐[1,2,4]triazine‐6‐ones ( 6 ) or ( 7 ). Aminoderivatives ( 7 ) were also obtained by reduction of nitro group of compounds ( 6 ). The aminoderivatives ( 7 ) were then cyclized to 3‐substituted‐1,5‐dihydro‐[1,2,4]triazino[6,5‐b]quinolines ( 9 ), resp. its tautomers ( 10 ).