Molybdate sulfuric acid/NaNO2: A novel heterogeneous system for the N-nitrosation of secondary amines under mild conditions

Wet molybdate sulfuric acid (= dioxo[bis(sulfato-kappa O)]molybdenum; MSA), a new solid acid, can be used in combination with sodium nitrite (NaNO2) to transform a variety of secondary amines to the corresponding N-nitroso compounds under mild, heterogeneous conditions (Table). The process has several advantages: the reagents are inexpensive and non-hazardous, the reaction is clean, fast, and high-yielding, and MSA can be readily removed by filtration and re-used (after treatment with HCl) without loss of activity. Further, only N-nitrosation was observed, but no C- or O-nitrosation.