Synthesis of 2-aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-thione and 2-aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-thione using 2-aroylaminomalonodiamide

Abstract

There are two strategic approaches to construct the azolopyrimidine system: via cyclization of the pyrimidine ring on an azole or by fusion of azole ring with the pyrimidine. In this work we used two approaches using 2-aroylaminomalonodiamides Ia–Ic as the starting materials [5]. In this case, the target products were 2-aryl-6H,7H-[1,3]oxazolo[5,4-d]pyrimidine-7-thiones Va–Vc and 2-aryl-6H,7H-[1,3]thiazolo[5,4-d]pyrimidine-7-thiones VIa–VIc. The reactions sequence I→II→IV→V has as the initial reaction that of 2-aroylaminomalonodiamides Ia–Ic with ethyl formate in the presence of sodium ethoxide to form 5-aroylamino-6-hydroxypyrimidin-4-ones IIa– IIc. The C NMR spectra of these compounds contain the characteristic signals of the C and C atoms of the pyrimidine ring in the ranges of 102.87–103.34 and 165.75–165.85 ppm, respectively. In the H NMR spectra there are no signals of the primary amide groups, and the singlet of СH proton appears in the range of 8.04–8.07 ppm.