Mechanism of the Formation of 3-Nitro-5-(3'-pyridyl)- Pyrazole from Nicotine

Natural Products Laboratory, School of Chemistry, University of Minnesota, Minneapolis, Minnesota, 55455, U.S.A.

The yield of 3-nitro-5-(3'-pyridyl) pyrazole, obtained by the oxidation of nicotine with nitric acid, was increased by the addition of sodium nitrite to the reaction mixture. Urea decreased the yield of this pyrazole, which was not obtained by the nitric acid oxidation of cotinine or nornicotine. The pyrazole derived from [1'-¹⁵N]-nicotine was enriched solely on the N-1 nitrogen. A mechanism consistent with these results and related work is presented to explain the formation of this pyrazole derivative.