Chemoselective N-nitrosation of secondary amines under heterogeneous and mild conditions via in situ generation of HNO2

A wide variety of secondary amines are chemoselectively subjected to N-nitrosation reaction with treatment of citric acid and NaNO2 in the presence of wet SiO2 (50%, w/w) in dichloromethane at room temperatture under heterogeneous conditions. The N-nitrosation method is very simple and products can be easily isolated with good to high yields.