The Preparation of 1H-Pyrazole-1-carboxylic Acid, 1, 1-Dimethylethyl Esters from Dilithiated C(α), N-Hydrazones of Hydrazinecarboxylic Acid, 1, 1-Dimethylethyl Ester

References

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• All chemicals were purchased from Aldrich Chemical Co
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• Infrared spectra were obtained from a Mattson Polaris or a Nicolet Impact 410 FT-Infrared Spectrometer. 1H nmr for 1—9 and 16 were obtained from a Varian Associates, EM-360L and compounds 10—15 were obtained on a EM-360A, Nuclear Magnetic Resonance Spectrometers, and chemical shifts are reported in δ ppm downfield from an internal tetramethylsilane (TMS) standard. [Compd. No., ir (paraffin oil), cm−1; nmr (solvent), δ ppm] Compd. 1: ir, 1762 (shoulders, C=O); nmr (CDCl3), 1.38 (s, OC(CH3)3), 2.53—3.22 (m, -CH2CH2-), and 7.20—8.40 (m, ArH). Compd. 2: ir, 1755 (shoulders, C=O); nmr (CDCl3), 1.37 (s, OC(CH3)3), 2.40—3.20 (m, -CH2CH2-), 3.88 and 3.90 (s, ArOCH3), and 7.17—8.33 (m, ArH). Compd. 3: ir, 3437 (OH), 1736 (shoulder, C=O); nmr (CDCl3), 1.38 (s, OC(CH3)3), 2.45—3.13 (m, -CH2CH2-), 3.87 (s, ArOCH3), and 6.92—8.32, (m, ArH). Compd. 4: ir, 1747 and 1703 (sh, C=O); nmr (CF3COOH), 1.63 (s, OC(CH3)3), 2.12—3.17 (m, -CH2CH2-), (-CH2- at C-4, uncertain assignment), 4.03 and 4.10 (s, ArOCH3), 7.03 (s, ArH), and 7.38—7.97 (m, ArH). Compd. 5: ir, 1748 (shoulders, C=O); nmr (CDCl3), 1.40 (s, OC(CH3)3), 3.87 (ArOCH3), 6.73 (s, C4-H), and 6.88—8.12 (m, ArH). Compd. 6: ir, 1751 (shoulders, C=O); nmr (DMSO-d6), 1.33 (s, OC(CH3)3), 3.73 and 3.83 (s, ArOCH3), 6.82 (s, C4-H), and 7.15—8.13 (m, ArH). Compd. 7: ir, 1763 (sharp, C=O); nmr (CDCl3), 1.40 (s, OC(CH3)3), 3.85 (s, ArOCH3), 6.67 (s, C4-H), and 6.90—8.10 (m, ArH). Compd. 8: ir, 3100—3200 (OH) and 1763 (shoulders, C=O); nmr (CDCl3), 1.48 (s, OC(CH3)3), 3.90 and 3.92 (s, ArOCH3), 6.68 (s, C4-H), and 6.75—7.80 (m, ArH). Compd. 9: ir, 1763 and 1730 (C=O); nmr (CDCl3), 1.38 (s, OC(CH3)3), 3.88 (s, ArOCH3), 6.68 (s, C4-H), and 6.70—7.63 (m, ArH). Compd. 10: ir, 3182 (NH), 1726 and 1699 (N-C(O)-O); nmr (DMSO-d6), 1.51 (s, OC(CH3)3), 1.62—3.00 (m, -CH2CH2CH2-), 7.02—7.40 and 7.90—8.23 (m, ArH). Compd. 11: ir, 3205 (NH), 1730 and 1707 (N-C(O)-O); nmr (DMSO-d6), 1.48 (s, OC(CH3)3), 0.88—1.13 and 1.75—2.78 (m, -(CH2)4-), and 6.65—7.8 (m, ArH). Compd. 12: ir, 3188 (NH), 1728, 1714, and 1691 (N-C(O)-O); nmr (DMSO-d6), 1.50 (s, OC(CH3)3), 2.22 (s, CH3-), and 7.35—8.00 (m, ArH). Compd. 13: ir, 3201 (NH), 1728 and 1703 (N-C(O)-O); nmr (DMSO-d6), 1.52 (s, OC(CH3)3), 2.20 (s, CH3-), 3.83 (s, ArOCH3), and 6.82—7.87 (m, ArH). Compd. 14: ir, 3193 (NH), 1728 and 1703 (N-C(O)-O); nmr (DMSO-d6), 1.52 (s, OC(CH3)3), 2.22 (s, CH3-), 3.83 (s, ArOCH3), and 6.85—7.45 (m, ArH). Compd. 15: ir, 3226, 3194, 3155 (OH and NH), and 1695 sh (N-C(O)-O); nmr (DMSO-d6), 1.53 (s, OC(CH3)3), 2.33 (s, CH3-), and 6.70—7.73 (m, ArH). Compd. 16: ir, 3543 and 3494 (NH and enol, OH), 1703 (C=O); nmr (DMSO-d6), 1.18 (s, OC(CH3)3), 2.38—3.10 (m, -CH2CH2-), 3.33 (s, enol, OH), 3.73 (s, ArOCH3), and 6.40—8.18 (m, ArH and NH)
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• Microanalyses for C, H, and N were obtained from Quantitative Technologies, Inc., Box 470, Salem Industrial Park, Whitehouse, NJ 08888 and Robertsons Laboratory, 29 Samson Avenue, Madison, NJ 07940 [Compd. No. from Table]. Calcd. for 1: C, 69.38; H, 5.56; N, 7.36. Found: C, 69.12; H, 5.58; N, 7.40. Calcd. for 2: C, 68.79; H, 6.47; N, 6.42. Found: C, 68.85; H, 6.46; N, 6.29. Calcd. for 3 (solvated): C, 72.23; H, 6.50; N, 7.32. Found: C, 72.43, 72.17; H, 6.78, 6.63; N, 7.09. Calcd. for 4: C, 69.31; H, 6.71; N, 6.21. Found: C, 69.01; H, 6.67; N, 6.17. Calcd. for 5: C, 65.54; H, 5.50; N, 7.28. Found: C, 65.73; H; 5.42; N, 7.30. Calcd. for 6: C, 62.09; H, 5.66; N, 6.30. Found: C, 61.91; H, 5.59; N, 6.24. Calcd. for 7: C, 65.54; H, 5.50; N, 7.28. Found: C, 65.54; H, 5.52; N, 7.33. Calcd. for 8 (solvated): C, 62.87; H, 6.59; N, 6.11. Found: C, 62.88; H, 6.78; N, 6.03. Calcd. for 9: C, 65.44; H, 6.41; N, 6.36. Found: C, 65.50; H, 6.48; N, 6.21. Calcd. for 10: C, 69.21; H, 7.74; N, 10.76. Found: C, 69.31; H, 7.68; N, 10.70. Calcd. for 11: C, 70.04; H, 8.08; N, 10.21. Found: C, 70.07; H, 8.23; N, 10.16. Calcd. for 12: C, 58.10; H, 6.38; N, 10.43. Found: C, 58.24; H, 6.52; N, 10.43. Calcd. for 13: C, 63.62; H, 7.63; N, 10.60. Found: C, 63.87; H, 7.47; N, 10.63. Calcd. for 14: C, 63.62; H, 7.63; N, 10.60. Found: C, 63.73; H, 7.61; N, 10.52. Calcd. for 15: C, 62.38; H, 7.25; N, 11.19. Found: C, 62.38; H, 7.27; N, 11.23. Calcd. for 16: C, 67.91; H, 6.65; N, 6.60. Found: C, 67.80; H, 6.62; N, 6.49
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• We would anticipate cleavage of the carbo-t-butoxy group under these conditions
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• Higher melting point N-H pyrazoles, if present, would have easily been isolated andidentified. See ref. 2
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