LETTER
Transesterification of b-Keto Esters Catalyzed by Cesium Fluoride
607
(5) Bandgar, B. P.; Uppalla, L. S.; Sadavarte, V. S. Synlett 2001,
1715.
Garavel, G.; Depres, J.-P.; Greene, A. E. J. Org. Chem.
1999, 64, 1380; and references cited therein.
(6) For recent leading references, see: (a) I2: Chavan, S. P.;
Kale, R. R.; Shivasankar, K.; Chandake, S. I.; Benjamin, S.
B. Synthesis 2003, 2695. (b) 3-Nitrobenzeneboronic acid:
Tale, R. H.; Sagar, A. D.; Santan, H. D.; Adude, R. N. Synlett
2006, 415. (c) Hexamethylenetetramine: Ribeiro, R. S.; de
Souza, R. O. M. A.; Vasconcellos, M. L. A. A.; Oliveira, B.
L.; Ferreira, L. C.; Aguiar, L. C. S. Synthesis 2007, 61; and
references cited therein.
(7) Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and
Practice; Oxford University Press: Oxford, 1998.
(8) Chavan, S. P.; Subbarao, Y. T.; Dantale, S. W.; Sivappa, R.
Synth. Commun. 2001, 31, 289.
(18) Cesium fluoride promoted desilylation of tert-
butyldimethylsilyl ethers was reported: Cirillo, P. F.; Panek,
J. S. J. Org. Chem. 1990, 55, 6071.
(19) Transesterification of normal esters proceeded under similar
reaction conditions. The details of this result will be
communicated later.
(20) Typical 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.
(21) Purchased from Mitsuwa Chemicals Co., Ltd.
(22) The equilibrium was shifted due to the loss of the relatively
volatile methyl, ethyl or isopropyl alcohol from the reaction
mixture.
(9) Hagiwara, H.; Koseki, A.; Isobe, K.; Shimizu, K.; Hoshi, T.;
Suzuki, T. Synlett 2004, 2188.
(10) (a) Bandgar, B. P.; Uppalla, L. S.; Sadavarte, V. S. Green
Chem. 2001, 3, 39. (b) da Silva, F. C.; Ferreira, V. F.;
Rianelli, R. S.; Perreira, W. C. Tetrahedron Lett. 2002, 43,
1165. (c) Jin, T.; Zhang, S.; Li, T. Green Chem. 2002, 4, 32.
(11) De Sairre, M. I.; Bronze-Uhle, E. S.; Donate, P. M.
Tetrahedron Lett. 2005, 46, 2705.
(12) For recent leading references, see: (a) LiClO4: Bandgar, B.
P.; Sadavarte, V. S.; Uppalla, L. S. Synlett 2001, 1338. (b)
NaBO3: Bandgar, B. P.; Sadavarte, V. S.; Uppalla, L. S.
Chem. Lett. 2001, 30, 894. (c) FeSO4: Bandgar, B. P.;
Sadavarte, V. S.; Uppalla, L. S. Synth. Commun. 2001, 31,
2063. Zn: (d) Chavan, S. P.; Shivasankar, K.; Sivappa, R.;
Kale, R. Tetrahedron Lett. 2002, 43, 8583. (e) Bandgar, B.
P.; Sadavarte, V. S.; Uppalla, L. S. J. Chem. Res., Synop.
2001, 16. (f) ZnSO4: Bandgar, B. P.; Pandit, S. S.; Uppalla,
L. S. Org. Prep. Proced. Int. 2003, 35, 219. (g) Polymer-
supported lipase: Cordova, A.; Janda, K. D. J. Org. Chem.
2001, 66, 1906. (h) Yttria-zirconia: Kumar, P.; Pandey, R.
K. Synlett 2000, 251.
(23) Selected spectroscopic data:
Octyl 2,2-Dimethyl-3-oxobutyrate: 1H NMR (CDCl3): d =
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):
d = 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): d = 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): d = 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): d =
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): d = 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.
(13) (a) Sato, T.; Yoshimatsu, K.; Otera, J. Synlett 1995, 845.
(b) Sato, T.; Otera, J. Synlett 1995, 336. (c) Sato, T.; Otera,
J. J. Org. Chem. 1995, 60, 2627.
(14) To the best of our knowledge, there is only one successful
report4 on the use of this type compound in the
transesterification process.
(15) CsF was the best catalyst among the cesium salts examined
under the identical conditions: CsCl (1%), CsBr (2%), CsI
(2%).
(16) Transesterification of b-keto esters with allylic alcohols is
rather difficult as it is offset by facile decarboxylative
rearrangement: (a) Carrol, M. F. J. Chem. Soc. 1940, 704.
(b) Kimel, W.; Cope, A. C. J. Am. Chem. Soc. 1943, 65,
1992.
2-(Dimethylamino)ethyl 3-Oxohexanoate: 1H NMR
(CDCl3): d = 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):
d = 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): d =
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): d = 13.4, 16.8, 25.0, 26.3,
28.2, 32.2, 44.7, 49.1, 65.0, 167.1, 202.6.
(17) Conventional acid- and base-catalyzed transesterification of
b-keto esters with propargylic alcohols provided in most
cases low yields of the products: Mottet, C.; Hamelin, O.;
Synlett 2008, No. 4, 605–607 © Thieme Stuttgart · New York