Reference of 2075-46-9, These common heterocyclic compound, 2075-46-9, name is 4-Nitro-1H-pyrazole, its traditional synthetic route has been very mature, but the traditional synthetic route has various shortcomings, such as complicated route, low yield, poor purity, etc, below Introduce a new synthetic route.
Step 1: Preparation of 3-chloro-1H-pyrazol-4-amine hydrochloride Into a 2 L three-necked round bottom flask affixed with an overhead stirrer, a temperature probe, an addition funnel, and a nitrogen inlet were added ethanol (600 mL) and 4-nitro-1H-pyrazole (50.6 g, 447 mmol). To this solution was added, in one portion, conc. HCl (368 mL) (note: rapid exotherm from 15 C. to 39 C.) and the resulting mixture was purged with nitrogen for 5 minutes. Palladium on alumina (5% w/w) (2.6 g, Alfa, black solid) was added to the mixture and stirred at room temperature while triethylsilane (208 g, 1789 mmol) was added drop-wise over 4 h. The reaction, which started to slowly exotherm from 35 C. to 55 C. over 2.0 h, was stirred for a total of 16 h and vacuum filtered through a plug of Celite to give a biphasic mixture. The mixture was transferred to a separatory funnel, the bottom aqueous layer was collected and rotary evaporated (60 C., 50 mmHg) to dryness with the aid of acetonitrile (3*350 mL). The resulting yellow solid was suspended in acetonitrile (150 mL) and allowed to stand for 2 h at room temperature followed by 1 h at 0 C. in the refrigerator. The solids were filtered and washed with acetonitrile (100 mL) to afford the titled compound 3-chloro-1H-pyrazol-4-amine hydrochloride (84 g, 97% yield, 80% purity) as a white solid: mp 190-193 C.; 1H NMR (400 MHz, DMSO-d6) delta 10.46-10.24 (bs, 2H), 8.03 (s, 0.54H), 7.75 (s, 0.46H), 5.95 (bs, 1H)); 13C-NMR (101 MHz, DMSO) delta 128.24, 125.97, 116.71.
Statistics shows that 4-Nitro-1H-pyrazole is playing an increasingly important role. we look forward to future research findings about 2075-46-9.