Chemistry Letters 2001
895
whereas other esters are found to be unreactive under these
reaction conditions.
VSS thanks CSIR, New Delhi for Junior Research
Fellowship.
Reference and Notes
1
S. Benetti, R. Ramagnoli, C. De Risi, G. Spalluto, and V.
Zanirato, Chem. Rev., 95, 1065 (1995).
2
a) T. Fujoita, M. Tanak, Y. Norimine, and H. Suemunc, J.
Org. Chem. 62, 3824 (1997). b) G. Shapiro and M. Marli,
J. Org. Chem., 62, 7096 (1997).
Even less reactive trityl alcohol afforded corresponding β-keto
ester in moderate yield (Table 1, entry 7) which is otherwise
often problematic in acid catalyzed reaction or failed to undergo
transesterification with Ti(OEt)4.4e It should be pointed out that
transesterification of β-keto esters with unsaturated alcohols is
rather difficult as it is offset by facile decarboxylated rearrange-
ment.13 The superiority of this procedure can be clearly visual-
ized in transesterifications leading to the synthesis of β-keto
esters with an aromatic moiety in good yields (Table 1, entries
9–12). In this connection it should be mentioned that a recent lit-
erature report14 which describes synthesis of alkyl β-keto esters
employing a tin based supper acid catalyst, failed with aromatic
substrates. It is also clear from the Table 1 that the conversion of
ethyl ester to higher homologue appears to be efficient by this
procedure. It is important to note that chiral integrity of (1R,2S,
5R)-(–)-menthol is mentained under these reaction conditions
(chiral alcohol is recovered by base hydrolysis of ester and its
optical rotation is checked, Table 1, entry 5). It is noteworthy to
mention that the reaction appears to be specific only for transfor-
mation of β-keto esters. Other esters like α-keto esters, γ-keto
esters as well as normal esters failed to undergo the reaction
(Table 1, entries 13–17). After scanning through different cata-
lysts (Table 2), we found that lithium perchlorate and sodium
perborate worked remarkably well. However, sodium perborate
is superior than lithium perchlorate as a catalyst in terms of cost
and its neutral nature.
3
4
P. Kumar and R. K. Pande, Synlett, 2, 251 (2000).
a) B. S. Balaji, M. Sasidharan, R. Kumar, and B. Chanda,
Chem. Commun., 1996, 707 b) B. C. Ranu, P. Dutta, and
A. Sarkar, J. Org. Chem., 63, 6027 (1998). c) B. M. Reddy,
V. R. Reddy and B. Manohar, Synth. Commun., 29, 1235
(1999). d) B. S. Balaji, B. M. Chanda, Tetrahedron, 54,
13237 (1998). e) P. Krasik, Tetrahedron Lett., 39, 4223
(1998). (f) S. Fukuzawa and Y. Hongo, Tetrahedron Lett.,
39, 3521 (1998).
D. F. Taber, J. C. Amedio Jr., and Y. K. Patle, J. Org.
Chem., 50, 3618 (1985).
J. S. Witzeman and W. D. Nottingham, J. Org. Chem., 56,
1713 (1991).
5
6
7
J. Otera, N. Danoh, and H. Nozaki, J. Org. Chem., 56,
5307 (1991).
A. Habi and D. Gravel, Tetrahedron Lett., 35, 4315 (1994).
C. Mottet, O. Hamelin, G. Garavel, J. Depres, and A. E.
Green, J. Org. Chem., 64, 1380 (1999).
8
9
10 B. Kumar, H. Kumar, and A. Parmar, Ind. J. Chem. B, 32,
292 (1993).
11 a) J. Muzart, Synthesis 1995, 1325. b) A. Mckillop W. R.
Sanderson, Tetrahedron, 51, 6145 (1995) c) A. Mckillon
W. R. Sanderson, J. Chem. Soc., Perkin Trans. 1, 2000,
471.
12 Typical procedure: A mixture of ethyl 3-(3,4,5-
trimethoxyphenyl)-3-oxopropanoate (5 mmol), 3,4-methyl-
enedioxycinnamyl alcohol (5 mmol), sodium perborate (1
mmol) in toluene (20 mL) was heated to 90–100 °C in a
round-bottom flask with distillation condenser to remove
ethanol. After completion (TLC) the reaction mixture was
cooled, filtered and filtrate was concentrated and chro-
matographed on SiO2 (hexane:ethyl acetate 9:1) to afford
(E)-3-(3,4-methylenedioxyphenyl)-2-propenyl 3-(3,4,5-
trimethoxyphenyl)-3-oxopropanoate. Yield 87%; IR (neat)
1
cm–1 3322, 1734, 1699; H NMR: (300 MHz, CDCl3), δ
3.98 (d, 9H) 4.12 (s, 2H), 4.7 (dd, J = 1.3 and 6 Hz, 2H),
5.90 (s, 2H), 6.0–6.15 (m, 1H), 6.5 (d, J = 14 Hz, 1H),
6.7–6.8 (m, 2H), 6.92 (s, 1H), 7.25 (s, 2H); 13C NMR: (60
MHz, CDCl3) δ 45, 55, 60, 65, 85, 102, 106, 107, 108, 121,
122, 131, 131.2, 134, 143, 148, 148.5, 153, 165, 192;
Anal. Calcd for C22H22O8 (414.42): C, 63.76; H, 5.35%
Found: C, 63.81; H, 5.28%
13 a) M. F. Carrol, J. Am. Chem. Soc., 1940, 704. b) W. Kimel
and A. C. Cope, J. Am.Chem. Soc., 65, 1992 (1943).
14 S. P. Chavan, P. K. Zubaidha, S. W. Dantale, A.
Keshavaraja, A. V. Ramaswami, and T. Ravindranathan,
Tetrahedron Lett., 37, 233 (1996).
In conclusion, we have developed an efficient and practical
method for transesterification of β-keto esters using sodium
perborate as an inexpensive catalyst. The effectiveness of this
protocol is manifested in its selectivity towards β-keto esters