Abstract A novel general method for the synthesis of isomeric 3 (4)-nitro-4 (3)-R-furoxans is developed. 3-Nitro isomers were obtained by reaction of hydroximoyl chlorides with dinitromethane sodium salt followed by conversion of the resulting 1-substituted 1- hydroxyimino-2, 2-dinitroethanes into dipotassium (or disodium salts) and their subsequent nitrosation with NaNO 2 in AcOH or with N 2 O 4. Thermal isomerization of 3-nitro isomers ...