Polycyclic heterocycles with acidic N-H group VII1 Synthesis of some polynuclear heterocyclic compounds derived from 5-phenyl-6-azauracil

Abstract

Diazonium salt 2 obtained by diazotisation of 3-[3-(6-azauracil-5-yl)-2- aminophenyl]-1,2-dihydro-quinoxalin-3-one 12 was used as a starting compound for the preparation of corresponding 2-hydroxy, 2-chloro, 2-bromo, and 2-iodo derivatives 4-7 using SN1 or Sandmeyer reaction. The diazonium salt 2 was converted by reductive cleavage to 3-[3-(6-azauracil-5-yl)phenyl]-1, 2-dihydro-quinoxalin-2-one 3 and its coupling with malononitrile or ethyl cyanoacetylcarbamate gave corresponding hydrazones 9 or 10. Hydrazone 9 was converted to 4-arylazo-3,5-diaminopyrazole 11 via cyclization with hydrazine, and hydrazone 10 was cyclized to 1-[2-(6-azauracil-5-yl)-6-(3,4-dihydro-3-oxo- quinoxalin-2-yl)phenyl]-6-azauracil-5-carbonitrile 12. The slow decomposition of diazonium salt 2 led to benzofuro- derivative 13 that was also found as an undesired side product of all the above mentioned SN1 reactions. Hydrazino derivative 8, which is an intermediate of diazonium salt 2 reduction or hydrazone 10 hydrolysis, was cyclized, without prior isolation, to corresponding derivative [1,2,4]triazino[5,6-c]cinnoline 14. ©ARKAT.