The [3+2] cycloaddition of nitrile oxides to nitriles is one of the most commonly used methods for the synthesis of 1,2,4-oxadiazoles [2,3]. In previous work [1], we have developed a synthesis of the 3,5-disubstituted isoxazoles using the reaction of acetylenes with 1,3,5-triazinylnitrile oxides generated by the thermolysis of the corresponding 1,3,5-triazin-6-ylnitroformaldoximes. In the present work, we have studied the possibility of obtaining (5-R-1,2,4-oxadiazol-3-yl)-1,3,5-triazines using the analogous [3+2] cycloaddition reactions of 1,3,5-triazinylnitrile oxides to nitriles. The reaction was carried out by heating a solution or suspension of nitroformaldoximes 1a-d in various nitriles. Formation of nitrogen oxides was observed upon heating, indicating the release of nitrous acid and the formation of nitrile oxides. However, at the end of the reaction as indicated by thin-layer chromatographic monitoring of the starting compounds 1a-d, 3,4-di-(4-R-6-methoxy-1,3,5-triazin-2-yl)-furoxanes 2a-d were isolated instead of the expected 2-R-4-methoxy-6-(5-R-1,2,4-oxadiazol-3-yl)-1,3,5-triazines (Scheme 1).Thus, under the conditions described above, nitrile does not participate in the reaction but rather acts as a solvent. Therefore, dimerization of the intermediate nitrile oxides occurs to give furoxanes 2a-d exclusively analogous to the process described in our previous work [4] instead of formation of (5-R-1,2,4-oxadiazol-3-yl)-1,3,5-triazines.