We sought to study the mechanism of the reaction in more detail. As previously mentioned, while we isolated nitro(hetero)arenes 5, the products of related ONSH reactions are frequently isolated as the reduced nitrosoarenes in the absence of an exogenous oxidant. We were unsure if we also accessed nitrosopyridine intermediates, but somehow our substrates happened to be oxidized by excess nitro(hetero)arene or by air.