Polycyclic heterocycles with acidic N-H group VI. The synthesis of some polycyclic heterocyclic compounds related to 3-phenyl-1,2-dihydro-quinoxaline-2-one

Abstract

This work deals with the study of the reactivity of substituted 3-(2-aminophenyl)-1,2-dihydroquinoxaline-2-ones (4a, 4b). 3-(2-Amino-4-fluorophenyl)-1,2-dihydroquinoxaline-2-one (4a) was prepared by the reaction of 6-fluoro-N-acetylisatin (2a) with 1,2-diaminobenzene and further hydrolysis of the acetyl group. Compound 4b was prepared directly by the reaction of 7-nitroisatin (1b) with 1,2-diaminobenzene. The cyclization reaction of compounds 4a, 4b in POCl 3 afforded indolo[2,3-b]quinoxalines 7a, 7b. Intramolecular splitting cyclizations of diazonium salts 5a, 5b led to [1]benzofuro[2,3-b]quinoxalines (6a, 6b) and azo-coupling reactions of diazonium salts 5a with ethyl cyanoacetylcarbamate and malonodinitrile gave arylhydrazones 9a and 10a. By the diazotization of amine 4b we were able to isolate diazotate 8b in sodium acetate solution. The azo-coupling reactions of diazotate 8b with ethyl cyanoacetyl carbamate and malonodinitrile gave the arylhydrazones 9b and 10b. These arylhydrazones were then transformed into 1,3-diaminopyrazoles (11a, 11b) and 6-azauracils (12a, 12b).

Efficient one pot preparation of novel 1-oxo-3-aryl-1,5-dihydrobenzo[4,5]imidazo[1,2-a]pyridine-2-carboxylic acid derivatives in a green solvent

“…14 Because the benzo [4,5]imidazo [1,2-a]pyridine scaffold show interesting biological activities, the synthesis of this group of compounds has been realised via several routes, including cycloaddition reactions, 6,9,15 condensation reactions, [16][17][18] multicomponent reactions, 10,[19][20][21][22][23] and multistep approaches. 5,[24][25][26] Also, metallic and non-metallic catalysts, [27][28][29][30] microwave irradiation, 31 and a series of transition metal catalysts have been used for the preparation of these compounds. 1,32 No doubt, the existing methods are useful, but also possess certain limitations such as an extended reaction time, special apparatus, high temperature, expensive catalysts, toxic solvents, and tedious workup processes.…”