Ethyl 2,3-dihydro-3-oxo-1H-pyrazole-4-carboxylate

3-Oxo-2, 3-dihydro-lH-pyrazole-4-carboxylic acid ethyl ester:[00358] To a solution of sodium ethoxide (20.8 g, 0.31 mol) and diethyl ethoxymethylenemalonate (20 mL, 0.10 mol) in ethanol (400 mL), was added hydrazine monohydrate (10.0 mL, 0.20 mol) with cooling in an ice-cold water bath. The mixture was then heated at 80 XX. Ethyl 3-oxo-2, 3-dihydro-1H-pyrazole-4-carboxylate A solution of diethyl 2-(ethoxymethylene)malonate (40 g, 185 mmol) in absolute ethanol (400 mL) was treated with hydrazine hydrate (8.99 mi, 185 mmol) dropwise. After approximately 20 min, 2N NaOH (25 mL) was added slowly (reaction in an ice-bath), then water (25 mL). The ice-bath was removed and the mixture stirred at rt for 1.5 hrs. The ethanol was removed in vacuo and the aqueous layer diluted with water (25 mL) and partitioned over EtOAc (100 mL). The aqueous layer was collected and cooled in an ice- bath. The pH was adjusted to 5 with 1M HCI, forming a precipitate. The precipitate was filtered, washing with water and dried in vacuo in the presence of CaCIThis compound was synthesized according to the method described in .To a 500-mL recovery flask, a 20percent solution of sodium ethoxide in ethanol (60 mL) and ethyl 2-(ethoxymethylene)malonate (10.5 mL, 524 mmol) were added, and the resulting mixture was stirred at room temperature for 10 minutes. To the obtained mixture, hydrazine monohydrate (5.1 mL, 104 mmol) was added, the resulting mixture was stirred at 80°C for 18 hours with heating, and then the obtained yellow suspension was cooled to 0°C. To the reaction solution vigorously stirred, 1 N hydrochloric acid (180 mL) was slowly added to the mixture at the same temperature to obtain a yellow solution. To the obtained solution, ethyl acetate (150 mL) was added, and the resulting mixture was stirred at room temperature for 1 hour. The organic layer was separated, and then the aqueous layer was extracted with ethyl acetate (100 mL x 2). The combined organic layers were dried over anhydrous sodium sulfate, and the insoluble substance was separated by filtration. The filtrate was concentrated under reduced pressure, and the obtained residue was crystallized by using ethyl acetate and hexane to obtain the title compound (2.82 g, 35percent) as yellow crystals (mixture of tautomers). MS ES M-H = 155Diethylethoxymethylenemalonate (7) (37.4 g, 0.172 mol) and hydrazine hydrochloride (12.2 g, 0.178 mol) were refluxed in ethanol (500 mL) for 16 hours.

Molecular Weight:156.14
XLogP3:0.2
Hydrogen Bond Donor Count:2
Hydrogen Bond Acceptor Count:4
Rotatable Bond Count:3
Exact Mass:156.05349212
Monoisotopic Mass:156.05349212
Topological Polar Surface Area:67.4
Heavy Atom Count:11
Complexity:222
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes