Preparation of Furazan Carboxylates from Enamines by a Nitrosation–Oxidative Cyclization Sequence

We report a telescoped nitrosation–oxidative cyclization sequence for preparing furazan (1,2,5-oxadiazole) carboxylic esters from the corresponding enamines. This method is mainly suitable for preparing furazan carboxylates substituted with aromatic rings. Preliminary process safety screening shows that our method offers advantages compared to the common dioxime dehydration method for preparing furazans.