Sheet silicate catalysed demethylation and Fischer-Hepp rearrangement of N-methyl-N-nitrosoaniline

N-methyl-N-nitrosoaniline (I) undergoes Fischer-Hepp rearrangement in clay microenvironment. Three different types of clays, K10-montmorillonite, KSF and bentonite clays (we found that the first two are active for this reaction) as well as cation-exchanged K10-montmorillonites are employed. In addition to the rearranged product, N-methyl-4-nitrosoaniline (IT), the solid state reaction also yields the denitrosation product, N-methylaniline, and the denitrosated as well as demethylated product, aniline. When the reaction is studied in various solvents with K10-montmorillonite clay, the rearranged product II is predominant in polar protic solvents. This may be due to the fact that there is a possibility of the formation of the corresponding alkyl nitrite in polar solvents which will favour nitrosation. When nitrite traps such as hydrazine, sulphamic acid or sodium nitrite are added in the clay-catalyzed reaction (both in the solid state and in the solvent), the rearrangement is completely stopped. Based on our experimental observations, an intermolecular rearrangement is proposed.