Pyrazole → Ethyl 2-(1H-pyrazol-1-YL)benzoate

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As described for the general reaction of ethyl 2-fluorobenzoate with amines set forth in Tetrahedron, 53, 7557-7576 (1997), ethyl 2-fluorobenzoate was reacted with pyrazole by refluxing N, N-dimethylformamide to give ethyl 2-(1-pyrazolyl)benzoate, as a thick yellow oil. Anal. Calc'd: for C12H12N2O2 : C, 66.7; H, 5.6; N 13.0: Found: C, 66.5: H, 5.4: N, 12.9; Mass spectrum (ES) 217.2 (M+H). A sample (7.02 g) of this compound and 8.42 ml of 5N NaOH in 40 ml of ethanol-tetrahydrofuran (2:1) was refluxed for 2 hrs and the solvent removed. The residue was made acidic (pH6) with 2N citric acid and the precipated solid was filtered to obtain 3.7g of product. The pH of the filtrate was adjusted to 4:5 and extracted with ethyl acetate The extract was concentrated to dryness to give 1.5 g of product. The two crops were combined to give 5.2 g of 2-(1-pyrazolyl)benzoic acid, mp 140-142° C. To the preceding compound (2.07 g) in 5 ml CH2Cl2 (chilled in an ice bath )was added 11.1 ml of a 2 Molar solution of oxalyl chloride in CH2Cl2 and 0.085 ml of N,N-dimethylformamide. The mixture was allowed to warm to room temperature and stirred for 4 hours. The solvent was removed and 25 ml of toluene added (twice) and removed under vacuum to give 2-(1-pyrazolyl)benzoyl chloride as a yellow solid.

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