An approach to fused pyrimidine derivatives via Schiff bases of aromatic ortho-nitrocarabaldehydes. An investigation of substituent effects on the reaction course

The synthesis of fused pyrimidines from the Schiff bases of aromatic orthon itrocarbaldehydes is reported. The Schiff bases after selective reduction o f the nitro group on 10% Pd/C, followed by condensation of the amines forme d with orthoesters, are transformed to corresponding imidates. Heating of t he latter in a sealed tube with an excess of ammonia (or with ammonia in et hanol) gives fused pyrimidines. The influence of various substituents in an aromatic ring of imine moiety of the Schift bases with regard to the overa ll yield of fused pyrimidine derivatives have been investigated. Moderate e lectron-withdrawing groups gave the best results.