A Simple and Environmentally Benign Nitration of Pyrazoles by Impregnated Bismuth Nitrate.

We report herein a facile, rapid, and environmentally friendly synthesis of nitropyrazoles in good yields using silica-bismuth nitrate and silica-sulfuric acid-bismuth nitrate at room temperature for the first time. The relatively non-toxic nature, ease of handling, easy availability, and low cost make the present procedure attractive for the nitration of a wide variety of diazoles in the drug and pharmaceutical industries.