The general procedure for the synthesis of 3-(2,5-dimethyl-1H-pyrrol-1-yl)-1-methyl-1H-pyrazole from 2,5-hexanedione and N-methyl-3-aminopyrazole was as follows: according to step 3-i of Scheme 3, 1-methyl-1H-pyrazol-3-amine (compound 1007, 2.8 g, 28.8 mmol) and 2,5-hexanedione (3.38 mL , 28.8 mmol) were dissolved in 50 mL of toluene. P-toluenesulfonic acid (1.4 mmol) was added, the reaction mixture was heated to reflux, and the water generated by the reaction was collected in a Dean-Stark manifold. When no more water was generated (about 4 hours), the reaction mixture was cooled and the solvent evaporated. The residue was purified by silica gel column chromatography using dichloromethane as eluent to give an oily product which solidified to a solid after standing. The solid was broken up, suspended in hexane, stirred vigorously for 1 hour and collected by filtration. 3-(2,5-dimethyl-1H-pyrrol-1-yl)-1-methyl-1H-pyrazole (compound 1008, 5.0 g, 98% yield) was finally obtained as a white powder. It was characterized by the following data: ESMS (M + 1) = 175; 1H-NMR (CDCl3) δ 7.38 (d, J = 4 Hz, 1H), 6.14 (d, J = 4 Hz, 1H), 5.84 (s, 2H), 3.95 (s, 3H), 2.09 (s, 6H).
