Compound 9: 2-(4-Methoxybenzyl)-2,4-dihydro-3H-pyrazol-3-one

DOI: 10.14469/hpc/11710 Metadata

Created: 2022-11-05 08:24

Last modified: 2024-05-28 08:54

Author: Henry Rzepa

License: Creative Commons: Public Domain Dedication 1.0

Funding: (none given)

Description

2-(4-Methoxybenzyl)-2,4-dihydro-3H-pyrazol-3-one (9): Aqueous KOH (2 M; 50 mL) was added with stirring to pyrazolone 8 (9.486 g, 34.33 mmol, 1.00 equiv) in EtOH and H2O (1 : 1; 20 mL). After heating at 100 °C for 18 h, the mixture was cooled to room temperature and acidified with aqueous HCl (4 M) to pH = 1 – 2. The mixture was further heated at 100 °C for 18 h, after which the mixture was cooled to room temperature and diluted with EtOAc (40 mL). The organic layer was separated, and the aqueous layer was further extracted with EtOAc (2 × 30 mL). The combined organic layers were washed with brine (40 mL), dried (MgSO4), filtered and concentrated under reduced pressure to give decarboxylated pyrazolone 9 (5.069 g, 24.83 mmol, 72%) as a yellow solid, essentially pure by its 1H NMR spectrum. Analytically pure samples were obtained by recrystallization from EtOH. Rf (hexanes : EtOAc 1 : 1) = 0.33. 1H-NMR Enol Form (400 MHz, CDCl3): δ (ppm) = 13.90 (s, 1H), 7.27 (d, J = 8.5 Hz, 2H), 7.25 (d, J = 3.4 Hz, 1H), 6.76 – 6.71 (m, 2H), 5.47 (d, J = 3.0 Hz, 1H), 5.10 (s, 2H), 3.69 (s, 3H). 1H-NMR Keto Form (400 MHz, CDCl3): δ (ppm) = 7.28 (d, J = 8.9 Hz, 2H), 7.26 (s, 1H), 6.86 (d, J = 8.1 Hz, 2H), 4.78 (s, 2H), 3.78 (s, 3H), 3.27 (s, 2H). 13C{1H}-NMR Enol Form (101 MHz, CDCl3): δ (ppm) = 159.4, 158.7, 134.1, 129.6, 126.9, 114.0, 90.7, 55.1, 47.9. 13C{1H}-NMR Keto Form (101 MHz, CDCl3): δ (ppm) = 171.5, 159.4, 146.4, 129.9, 128.6, 114.2, 55.4, 47.6, 39.6. IR (Diamond-ATR, neat) νmax (cm-1) = 2344, 1706, 1610, 1559, 1508, 1402, 1359, 1301, 1280, 1206, 1174, 1115, 1031, 938, 835, 922, 816, 774, 749, 736. HRMS (ES-ToF) m/z: [M + H]+ calc. for (C11H13N2O2)+: 205.0972, found: 205.0979. m.p.: 111 – 114 °C (EtOH) (lit.[4] m.p. 135 °C). Anal. Calcd for C11H12N2O2: C, 64.69; H, 5.92; N; 13.72. Found: C, 65.24; H, 5.91; N, 12.70. The analytic data were in good agreement with literature values.[4]

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DOIDescription
10.14469/hpc/10386 Syntheses and Characterization of Main Group, Transition Metal, Lanthanide and Actinide Complexes of Bidentate Acylpyrazolone Ligands

Members

DOIDescription
10.14469/hpc/11829 NMR Data for Compound 9.
10.14469/hpc/11835 IR Data for Compound 9.

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