S. Sano et al. / Tetrahedron Letters 46 (2005) 2883–2886
2885
3. Nagao, Y.; Sano, S. J. Synth. Org. Chem., Jpn. 2003, 61,
1088–1098, and references cited therein.
R
O
4. Nagao, Y. Yakugaku Zasshi 2002, 122, 1–27, and refer-
ences cited therein.
5. Moloney, M. G.; Pinhey, J. T.; Roche, E. G. J. Chem.
Soc., Perkin Trans. 1 1989, 333–341.
6. Pinhey, J. T. Aust. J. Chem. 1991, 44, 1353–
1382.
7. Hashimoto, S.; Miyazaki, Y.; Shinoda, T.; Ikegami, S. J.
Chem. Soc., Chem. Commun. 1990, 1100–1102.
OEt
powdered
KOH
n
O
n
-Bu4N+OH
1a-c n = 1
2a-c n = 2
EtOH
excess
EtOH
(1.1 mol eq)
n
-Bu4N+Br
H2O
small
THF
EtOH - THF
(1 : 2.5)
H2O
(1.25 mol eq)
0 ˚C, 15 min
KBr
n
-Bu4N+OEt
rt, 12 h
8. The spectroscopic data of 1a and 2a are as follows:
Compound 1a: pale yellow oil; 1H NMR (400 MHz,
CDCl3): d 1.32 (3H, t, J = 7.3 Hz), 2.10–2.16 (2H, m), 2.34
(3H, s), 2.39–2.44 (2H, m), 2.46–2.54 (1H, m), 2.65–2.73
(1H, m), 4.27 (2H, q, J = 7.3 Hz), 7.10 (2H, d, J = 7.8 Hz),
7.34 (2H, d, J = 7.8 Hz); 13C NMR (100 MHz, CDCl3): d
14.06, 19.92, 21.49, 36.76, 36.94, 56.58, 62.45, 83.83, 85.20,
119.40, 128.93, 131.82, 138.62, 168.63, 208.12; IR (neat)
2981, 2228, 1763, 1741, 1510 cmÀ1; EI-MS calcd for
C17H18O3 MW 270.1256, found m/e 270.1263 (M+).
Compound 2a: pale yellow oil; 1H NMR (200 MHz,
CDCl3): d 1.33 (3H, t, J = 7.1Hz), 1.75–2.55 (7H, m),
2.88–3.04 (1H, m), 4.30 (2H, dq, J = 2.4 and 7.1Hz), 7.12
(2H, d, J = 8.1Hz), 7.35 (2H, d, J = 8.1Hz); 13C NMR
(100 MHz, CDCl3): d 14.06, 21.49, 21.60, 27.45, 37.36,
38.72, 56.59, 62.14, 84.36, 87.78, 119.44, 129.02, 131.69,
138.73, 168.67, 203.15; IR (neat) 2943, 2227, 1743, 1725,
1511 cmÀ1; EI-MS calcd for C18H20O3 MW 284.1412,
found m/e 284.1404 (M+). Anal. Calcd for C18H20O3: C,
76.02; H, 7.09. Found: C, 75.64; H, 7.19.
R
H
O
10a 94%
10b 71%
10c 63%
11a 92%
11b 64%
11c 48%
a: R =
Me
OEt
•
O
OEt
b: R =
c: R =
n-Pr
n
10a-c n = 2
11a-c n = 3
Scheme 4.
Finally, we have attempted a new type of mild retro-
Dieckmann-type ring-opening reaction of 1a–c and
2a–c with n-Bu4N+OEtÀ generated in situ by treatment
of powdered KOH with excess EtOH–THF in the pres-
ence of n-Bu4N+BrÀ as a phase transfer catalyst in the
solid–liquid system12,13 as follows (Scheme 4). After
treatment of 1.1 mol equiv of powdered KOH and
1.25 mol equiv of n-Bu4N+BrÀ in a solution of EtOH
and THF at room temperature for 12 h, the mixture
was supplemented with a solution of 1a at 0 °C in
THF. After stirring at 0 °C for 15 min, the usual workup
of the reaction mixture gave the desired compound 10a
as a pale yellow oil in 94% yield. The similar treatment
of 1b,c, and 2a–c furnished the corresponding allenyl
diesters 10b (71% yield), 10c (63% yield), 11a (92%
yield), 11b (64% yield), and 11c (48% yield), respectively.
The structures of all products were assigned based on
the similarity of their spectroscopic data to those of
8a–c and 9a–c, except for the data of the carboxyl
group.14 Thus, we have achieved formation of ethyl
esters 10a–c and 11a–c without the use of NaOEt.
9. Nagao, Y.; Kim, K.; Sano, S.; Kakegawa, H.; Lee, W.-S.;
Shimizu, H.; Shiro, M.; Katunuma, N. Tetrahedron Lett.
1996, 37, 861–864.
10. The spectroscopic data of 8a and 9a are as follows:
Compound 8a: colorless plates (AcOEt/n-hexane), mp 86–
88 °C; 1H NMR (400 MHz, CDCl3): d 1.24 (3H, t,
J = 7.3 Hz), 1.79–1.87 (2H, m), 2.34 (3H, s), 2.37–2.46
(4H, m), 4.20 (2H, q, J = 7.3 Hz), 6.54 (1H, t, J = 2.9 Hz),
7.14 (2H, d, J = 8.3 Hz), 7.17 (2H, d, J = 8.3 Hz); 13C
NMR (100 MHz, CDCl3): d 14.20, 21.19, 22.96, 28.19,
33.33, 61.13, 98.60, 103.44, 127.13, 129.18, 129.52, 137.70,
166.58, 179.30, 211.82; IR (KBr) 2981, 2361, 1943, 1709,
1514 cmÀ1; EI-MS calcd for C17H20O4 MW 288.1362,
found m/e 288.1366 (M+). Anal. Calcd for C17H20O4: C,
70.81; H, 6.99. Found: C, 75.86; H, 7.11. Compound 9a:
colorless plates (AcOEt), mp 64–71 °C; 1H NMR
(400 MHz, CDCl3): d 1.25 (3H, t, J = 7.3 Hz), 1.52–1.59
(2H, m), 1.65–1.72 (2H, m), 2.34 (3H, s), 2.29–2.42 (4H,
m), 4.20 (2H, q, J = 7.3 Hz), 6.52 (1H, t, J = 2.9 Hz), 7.13
(2H, d, J = 8.3 Hz), 7.17 (2H, d, J = 8.3 Hz); 13C NMR
(100 MHz, CDCl3): d 14.27, 21.23, 24.16, 27.40, 28.50,
33.71, 61.10, 98.37, 103.84, 127.14, 129.53, 131.64, 137.65,
166.77, 179.53, 211.89; IR (KBr) 2935, 1943, 1738, 1709,
1514 cmÀ1; EI-MS calcd for C18H22O4 MW 302.1518,
found m/e 302.1512 (M+).
In conclusion, we have demonstrated methods for the
facile and mild synthesis of the conjugated allenyl esters
based on the retro-Dieckmann-type ring-opening reac-
tions employing 1N KOH and n-Bu4N+OEtÀ; these
methods will be available as new trigger reactions for
various bioorganic and chemical cascade reactions.3,4,15
Acknowledgements
11. The crystallographic data of 8a is as follows: C17H20O4,
˚
M = 288.34, monoclinic, P21/c (#14), a = 10.521(5) A,
This work was supported by a Grant-in-Aid for Scien-
tific Research (B) (2) (No. 16390008) from the Japan
Society for the Promotion of Science. We also extend
our thanks to Professor Masafumi Goto (Kumamoto
University) for the X-ray crystallographic analysis.
˚
˚
b = 5.327(7) A, c = 28.906(4) A, b = 100.00(2)°, V =
3
1595(2) A , Z = 4, Dcalcd = 1.200 g cmÀ3
,
l(Mo Ka) =
˚
0.85 cmÀ1
.
12. Dehmlow, E. V.; Dehmlow, S. S. Phase Transfer Cataly-
sis. In Monographs in Modern Chemistry; Ebel, H. S., Ed.;
Chemie: Florida, 1980.
13. Ooi, T.; Maruoka, K. J. Synth. Org. Chem., Jpn. 2003, 61,
1195–1206.
References and notes
14. The spectroscopic data of 10a and 11a are as follows:
Compound 10a: pale yellow oil; 1H NMR (400 MHz,
CDCl3): d 1.22 (3H, t, J = 7.3 Hz), 1.25 (3H, t, J = 7.3 Hz),
1.80–1.87 (2H, m), 2.30–2.43 (4H, m), 2.34 (3H, s), 4.10
1. Schuster, H. F.; Coppola, G. M. Allenes in Organic
Syntheses; Wiley: New York, 1984.
2. Smadja, W. Chem. Rev. 1983, 83, 263–320.