Reference of 5932-27-4, These common heterocyclic compound, 5932-27-4, name is Ethyl 1H-pyrazole-3-carboxylate, 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.
1 – ( [2-(trimethylsilyl)ethoxy]methyl) – lH-pyrazole-3 -carbaldehyde was prepared as follows: 3-Methyl pyrazole (50 g, 0.61 mol) was placed in a 5 L round-bottom flask equipped with mechanical stirrer. 3 L of water was added and heated to 80 C. KMn04 (211.90 g, 1.34 mol) was added portion wise and refluxed for 4.5 h. After stirring at rt overnight, solid was filtered and washed with water. The water was removed in vacuo and 100 mL of water was kept in the flask which was acidified with 1 N HCl to pH 4. It was extracted with EtOAc (2x 1L), washed with brine (2×150 mL), dried over MgS04, filtered and removed in vacuo to yield 1H-pyrazole-3-carboxylic acid (38 g, 56percent) as a white solid. 38 g (0.34 mol) of IH-pyrazole-3-carboxylic acid was refluxed in anhydrous ethanol (1 L) and conc. sulfuric acid (60 mL) for 20 h under nitrogen. Ethanol was removed and crude was basified to pH 8. Precipitated solid was filtered. The filtrate was extracted with THF/CHC13 (2: 3, 3x 1 L), dried over MgS04, filtered and removed in vacuo to yield ethyl 1H-pyrazole-3- carboxylate (39 g, 82percent) as a white solid. To a suspension of ethyl 1H-pyrazole-3-carboxylate (4.42 g, 31.57 mmol) in 1,4-dioxane (140 mL) under N2 atmosphere at 0 C was added NaH (0.91 g, 37.88 mmol) and stirred for 15 min. Neat SEM-Cl (5.79 g, 34.73 mmol) was added drop wise to reaction mixture and stirred overnight at rt. It was quenched with water (30 mL) and excess 1,4-dioxane was removed in vacuo. The residue was extracted with EtOAc (2×250 mL), washed with water (1×50 mL), dried over MgS04, filtered and removed in vacuo to give crude ethyl 1 – {[2- (trimethylsilyl)ethoxy]methyl}-1H pyrazole-3-carboxylate (8.84 g) as a yellow oil. The crude material was used in next step without purification. To a suspension of LiAlH4 in THF (100 mL) at 0 C under N2 atmosphere was added a solution of ethyl 1- f [2-(trimethylsilyl)ethoxy]methyl}-1H pyrazole-3-carboxylate (8.88 g, 32.88 mmol) slowly. After addition was completed the cooling bath was removed and reaction mixture was stirred overnight. It was quenched with water (10 mL) carefully at 0 C. THF was removed and residue was diluted with DCM (250 mL) and organic layer was separated, dried over MgS04 and removed in vacuo. The crude material was plugged thru a pad of silica gel with EtOAc/hexanes (from 10percent to 100percent) to yield (1-{[2- (trimethylsilyl)ethoxy]methyl) -lH-pyrazol-3-yl)methanol (5.80 g, 77percent) as an yellow oil. 53.75 g (0.24 mol) of (1- f [2-(trirnethylsilyl)ethoxy]methyl}-1H pyrazol-3-yl)methanol was dissolved in THF and 122.97 g (1.41 mol) of Mn02 was added. The resulting mixture was refluxed for 60 h. Solid material was filtered through a pad of celite and washed with hot THF. The filtrate was removed in vacuo to give crude product. The crude was plugged thru a pad of silica gel and eluted with EtOAc/hexanes (from 20percent to 50percent) to yield 1-{[2- (trimethylsilyl)ethoxy]methyl}-1H pyrazole-3-carbaldehyde (50.88 g, 86.5percent) as a red oil.
Statistics shows that Ethyl 1H-pyrazole-3-carboxylate is playing an increasingly important role. we look forward to future research findings about 5932-27-4.
Reference:
Patent; ASTRAZENECA AB; WO2005/111001; (2005); A1;,
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics