Sulfuric Acid → 2-(3-Difluoromethyl-5-phenyl-pyrazol-1-yl)-5-methanesulfonyl-pyridine

Participants

Reaction Conditions

Reaction Steps

To a clean and dry nitrogen purged 1 L round-bottom flask under nitrogen atmosphere was charged 25.6 g of 5-(methylsulfonyl)-2-hydrazinyl-pyridine (0.14 moles), 512 mL water (20 volumes) and 16 mL of concentrated H2SO4 (0.063 volumes). In a separate 500 mL 1-neck round-bottom flask, was prepared a solution of 384 mL of isopropanol (15 volumes) and 26.01 g (0.13 moles) of 4,4-difluoro-1-phenyl-1,3-butanedione. The isopropanol/4,4-difluoro-1-phenyl-1,3-butanedione solution was added to the 5-(methylsulfonyl)-2-hydrazinyl-pyridine reaction mixture keeping the pot temperature less than 25° C. After addition, the mixture was stirred at 22° C. for 2.0 hours and sampled for disappearance of starting material. When the starting materials had disappeared (less than 15 remaining), the pot was then heated to 40° C. for 5.5 hours until disappearance of the intermediate. The resulting slurry was filtered and washed with water to achieve a pH 6-7 of the filtrate. The solids were then charged to a 250 mL 3-neck round-bottom flask. To the flask was added: 31.25 mL water (1.2 volumes) and 31.25 mL isopropanol (1.2 volumes). The mixture was heated to reflux (85° C.) for 30 minutes. The pot was allowed to cool to 28° C. and the solids were isolated by filtration and washed with 20 mL isopropanol. The solids were dried in a vacuum oven at 45° C. The product was obtained with 87% yield and contained 0.54% of the compound of formula 6 (retention time 5.1 minutes). Analytical data: HPLC retention time (title compound) 8.4 minutes; MS: 349.36 (calc), M+1=350.1; 1H NMR in CDCl3: 8.75 doublet, (1H), 8.26 Quartet (1H), 7.38 multiplet (3H), 7.36 doublet (2H), 6.70 multiplet (2H), 3.08, Singlet, (3H); 13C NMR in CDCl3: 15.3, 149.3, 147.9, 146.6, 138.1, 130.27, 133.5, 130.0, 129.1, 128.7, 117.9, 113.4, 111.1, 108.1, 107.7, 45.

Provenance & Evidence