Compound 8: Ethyl 2-(4-Methoxybenzyl)-3-oxo-2,3-dihydro-1H-pyrazole-4-carboxylate
DOI: 10.14469/hpc/11709 Metadata
Created: 2022-11-05 08:22
Last modified: 2024-05-28 08:21
License: Creative Commons: Public Domain Dedication 1.0
Funding: (none given)
Description
Ethyl 2-(4-Methoxybenzyl)-3-oxo-2,3-dihydro-1H-pyrazole-4-carboxylate (8): Diethyl ethoxymethylenemalonate (4) (8.030 g, 7.510 mL, 37.10 mmol, 1.00 equiv) was added with stirring to K2CO3 (5.128 g, 37.10 mmol, 1.00 equiv) and PMB-hydrazine hydrochloride 7 (7.000 g, 37.10 mmol, 1.00 equiv) in H2O (180 mL). After heating at 100 °C for 18 h, 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 aqueous NaOH (2 M; 30 mL). The combined aqueous layers were acidified with aqueous HCl (4 M) to pH = 1 – 2, and extracted with EtOAc (3 x 50 mL). The combined organic layers were washed with brine (40 mL), dried (Na2SO4), filtered and concentrated under reduced pressure to give pyrazolone 8 (9.486 g, 34.59 mmol, 93%) as an off-white or yellow solid, essentially pure by its 1H NMR spectrum. Analytically pure samples were obtained by recrystallization from EtOH. Rf (hexanes : EtOAc 1 : 1) = 0.06. 1H-NMR (400 MHz, CDCl3): δ (ppm) = 7.59 (d, J = 1.4 Hz, 1H), 7.25 – 7.22 (m, 2H), 6.86 – 6.82 (m, 2H), 5.07 (s, 2H), 4.29 (qd, J = 7.1, 1.4 Hz, 2H), 3.76 (d, J = 1.4 Hz, 3H), 1.33 (td, J = 7.1, 1.4 Hz, 3H). 1H-NMR (400 MHz, CD3OD): δ (ppm) = 7.65 (s, 1H), 7.21 – 7.14 (m, 2H), 6.89 – 6.81 (m, 2H), 5.04 (s, 2H), 4.25 (q, J = 7.1 Hz, 2H), 3.74 (s, 3H), 1.30 (t, J = 7.1 Hz, 3H). 13C{1H}-NMR (101 MHz, CDCl3): δ (ppm) = 165.7, 159.3, 156.0, 138.0, 129.4, 127.8, 114.1, 94.3, 60.4, 55.2, 50.0, 15.3. 13C{1H}-NMR (101 MHz, CD3OD): δ (ppm) = 164.9, 160.8, 156.4, 140.1, 130.1, 129.5, 115.0, 96.8, 60.9, 55.7, 50.3, 14.8. IR (Diamond-ATR, neat) νmax (cm-1) = 2583, 1685, 1536, 1510, 1370, 1336, 1244, 1163, 1090, 1027, 793, 779, 724, 691. HRMS (ES-ToF) m/z: [M + H]+ calc. for (C14H17N2O4)+: 277.1183, found: 277.1188. m.p.: 102 – 105 °C (EtOH) (lit.[4] m.p. 105 °C). Anal. Calcd for C14H16N2O4: C, 60.86; H, 5.84; N; 10.14. Found: C, 60.82; H, 5.81; N, 10.12. The analytic data were in good agreement with literature values.[4]
Member of collection / collaboration
| DOI | Description |
|---|---|
| 10.14469/hpc/10386 | Syntheses and Characterization of Main Group, Transition Metal, Lanthanide and Actinide Complexes of Bidentate Acylpyrazolone Ligands |
Members
| DOI | Description |
|---|---|
| 10.14469/hpc/11828 | NMR Data for Compound 8. |
| 10.14469/hpc/11833 | IR Data for Compound 8. |
Associated DOIs
| Current dataset ... | DOI | Description |
|---|---|---|
| References | 10.1002/chin.200515113 | The 4-Methoxybenzyl (PMB) Function as a Versatile Protecting Group in the Synthesis of N-Unsubstituted Pyrazolones. |