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DOI: 10.1055/s-2008-1032071
A Simple and Efficient Method for Transesterification of β-Keto Esters Catalyzed by Cesium Fluoride
Publication History
Publication Date:
23 January 2008 (online)
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Abstract
Cesium fluoride is found to be an efficient and reusable catalyst for the transesterification of β-keto esters with various alcohols in good to high yields.
Key words
alcohols - β-keto esters - catalysis - cesium fluoride - transesterifications
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References and Notes
To the best of our knowledge, there is only one successful report4 on the use of this type compound in the transesterification process.
15CsF was the best catalyst among the cesium salts examined under the identical conditions: CsCl (1%), CsBr (2%), CsI (2%).
19Transesterification of normal esters proceeded under similar reaction conditions. The details of this result will be communicated later.
20Typical Procedure (Table 1, entry 1): In a 65-mL test tube (2.0 × 19 cm) fitted with a Drierite drying tube, a vigorously stirred mixture of methyl acetoacetate (581 mg, 5.0 mmol), 1-octanol (846 mg, 6.5 mmol) and CsF21 (76 mg, 0.5 mmol) in commercial toluene without any purification (10 mL) was heated so that the toluene refluxed halfway up the tube (130-135 °C, bath temperature) for 18 h.22 After toluene had been decanted, CsF was washed with Et2O (5 mL). The combined organic layer was evaporated under reduced pressure. The residue was chromatographed on silica gel (5% EtOAc-hexane) to afford octyl acetoacetate (997 mg, 93%).23 CsF remained intact and was reused for the subsequent reaction.
21Purchased from Mitsuwa Chemicals Co., Ltd.
22The equilibrium was shifted due to the loss of the relatively volatile methyl, ethyl or isopropyl alcohol from the reaction mixture.
23Selected spectroscopic data:
Octyl 2,2-Dimethyl-3-oxobutyrate: 1H NMR (CDCl3): δ = 0.88 (t, J = 7.5 Hz, 3 H), 1.22-1.66 (m, 12 H), 1.36 (s, 6 H), 2.16 (s, 3 H), 4.12 (t, J = 7.0 Hz, 2 H). 13C NMR (CDCl3): δ = 13.9, 21.7, 22.5, 25.5, 25.7, 28.3, 29.0, 31.6, 55.6, 65.3, 173.5, 205.6.
2-Heptynyl 3-Oxohexanoate: 1H NMR (CDCl3): δ = 0.91 (t, J = 7.5 Hz, 3 H), 0.93 (t, J = 7.5 Hz, 3 H), 1.36-1.44 (m, 2 H), 1.46-1.53 (m, 2 H), 1.59-1.67 (m, 2 H), 2.22 (tt, J = 2.5, 7.5 Hz, 2 H), 2.53 (t, J = 7.5 Hz, 2 H), 3.47 (s, 2 H), 4.72 (t, J = 2.5 Hz, 2 H). 13C NMR (CDCl3): δ = 13.4, 16.8, 18.3, 21.8, 30.3, 44.7, 48.9, 53.5, 73.3, 88.0, 166.5, 202.1.
8-Oxiranyloctyl 3-Oxohexanoate: 1H NMR (CDCl3): δ = 0.93 (t, J = 7.5 Hz, 3 H), 1.25-1.69 (m, 16 H), 2.47 (dd, J = 3.5, 5.0 Hz, 1 H), 2.52 (t, J = 7.5 Hz, 2 H), 2.75 (app t, J = 4.5 Hz, 1 H), 2.88-2.94 (m, 1 H), 3.43 (s, 2 H), 4.13 (t, J = 6.5 Hz, 2 H). 13C NMR (CDCl3): δ = 13.4, 16.8, 25.6, 25.8, 28.3, 28.9, 29.1, 29.2, 32.3, 44.7, 46.9, 49.1, 52.2, 65.3, 167.2, 202.6.
2-(Dimethylamino)ethyl 3-Oxohexanoate: 1H NMR (CDCl3): δ = 0.93 (t, J = 7.0 Hz, 3 H), 1.58-1.68 (m, 2 H), 2.28 (s, 6 H), 2.52 (t, J = 7.0 Hz, 2 H), 2.58 (t, J = 5.5 Hz, 2 H), 3.47 (s, 2 H), 4.24 (t, J = 5.5 Hz, 2 H). 13C NMR (CDCl3): δ = 13.3, 16.7, 44.7, 45.4, 49.0, 57.4, 62.6, 167.1, 202.6.
6-Chlorohexyl 3-Oxohexanoate: 1H NMR (CDCl3): δ = 0.93 (t, J = 7.5 Hz, 3 H), 1.35-1.82 (m, 10 H), 2.52 (t, J = 7.5 Hz, 2 H), 3.43 (s, 2 H), 3.54 (t, J = 6.5 Hz, 2 H), 4.14 (t, J = 7.0 Hz, 2 H). 13C NMR (CDCl3): δ = 13.4, 16.8, 25.0, 26.3, 28.2, 32.2, 44.7, 49.1, 65.0, 167.1, 202.6.