X-Ray analysis of 6-ethoxycarbonyl-4-ethylpyrazolo[1,5-a]pyrimidin-7(4H)-one and 6-ethoxycarbonyl-4-ethyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one

Abstract

The product obtained by treating 6-ethoxycarbonyl-7-hydroxypyrazolo[1,5-a]pyrimidine (2a) with ethyl iodide is shown by X-ray analysis to be 6-ethoxycarbonyl-4-ethylpyrazolo[1,5-a]pyrimidin-7(4H)-one (3a). When 3-amino-1,2,4-triazole (5a) was cyclised with diethyl ethoxymethylenemalonate the product was shown to have the structure (2b), rather than (6), by an X-ray analysis of its N-ethyl derivative, 6-ethoxycarbonyl-4-ethyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (3d). Carbon-13 chemical shift values in the above and related compounds have been assigned.