This paper is dedicated to Professor Teruaki
Mukaiyama in celebration of the 40th anniversary of the
Mukaiyama aldol reaction.
10 Catalyzed by heterogeneous catalysts: a) H. Ohki, M. Wada,
c) C. L. Roux, H. Gaspard-Iloughmane, J. Dubac, J. Jaud, P.
Ciliberti, H. Laurent-Robert, A. Laporterie, J. Dubac, Synlett
References and Notes
1
John Wiley & Sons, New York, 1982, Vol. 28, pp. 203-331.
11 Supporting Information is available electronically on the CSJ-
2
Based on our calculations using Gaussian 03W18 at the
B3LYP/6-31+G(d) level, the free energy difference, ¦G, of
the Mukaiyama aldol reaction of a silicon enolate, 2-(trimeth-
ylsiloxy)propene, with acetone is much lower than that with
acetaldehyde (¹4.9 kcal mol¹1 vs. ¹11.4 kcal mol¹1). The high-
er the ¦G, the higher the activation energy ¦G‡, according to
the Bell-Evans-Polanyi principle: S. Roy, S. Goedecker, V.
reaction with protonated acetone was higher than that with
12 The plausible reaction pathways are shown in Figure S1.
13 Twenty milligrams of Sn-Mont contain 0.042 mmol of tin atom
which corresponds to 4.2 mol % of 1a. Therefore, 5 mol % of
each homogeneous acid was employed for the control reactions.
14 This is the first example of the formation of 5aa by dehydration
from 4aa. It is plausible that the less stable 5aa rather than the
α,β-unsaturated ketone product is mainly formed through the
stable 6-membered transition state in the dehydration step (See
Figure S2). The other synthetic methods for 5aa: a) M.-K. Zhu,
Kovalev, Y. I. Lyakhovetskii, M. M. Teplyakov, A. L. Rusanov,
1529. e) X. Yu, L. Wang, X. Feng, M. Bao, Y. Yamamoto,
¹1
protonated acetaldehyde (17.4 kcal mol vs. 15.9 kcal mol¹1).
3
4
5
6
7
a) J. Wang, Y. Masui, K. Watanabe, M. Onaka, Adv. Synth.
Kogure, T. Tanaka, M. Onaka, submitted.
15 The TG analysis showed that the residual water in Sn-Mont was
removed over 150 °C. See Figure S3.
16 There have been no successful examples of the aldol reactions
of 1e with ketone enolates to the best of our knowledge, but
only a few examples were reported for the reactions of 1e with
ester enolates. Use of Lewis bases: a) M. Hatano, E. Takagi, K.
Lewis acid: c) R. Nagase, J. Osada, H. Tamagaki, Y. Tanabe,
Sn-Mont was prepared as follows: Na-Mont (cation-exchange
capacity: 1.19 mequiv g¹1, 8 g) was ion-exchanged with aq.
SnCl4¢5H2O (0.30 M, 80 mL) at room temperature (RT) for
2 h, and this exchange process was repeated. The clay was
collected, and successively washed twice with water (80 mL),
six times with a mixture of water (40 mL) and methanol
(40 mL), and finally once with absolute methanol (80 mL). The
clay was dried in a 0.5 Torr vacuum at RT for 12 h, followed by
being ground in a mortar with a pestle and passed through a
60-mesh screen. Sn-Mont contained 2.1 mmol of tin atom per
gram of Sn-Mont determined by inductively coupled plasma
(ICP) analysis. The specific surface area of Sn-Mont was as
high as 380 m2 g¹1, which was about 17 times that of the
pristine Na-Mont (22 m2 g¹1).
17 According to our calculations, the free energy difference ¦G of
the Mukaiyama aldol reaction of acetone with a ketone enolate,
2-(trimethylsiloxy)propene, is greater than that of acetone with
an ester enolate, 1-methoxy-2-(trimethylsiloxy)propene (¹4.9
¹1
kcal mol vs. ¹19.4 kcal mol¹1), and the ¦G‡ of the reaction
of protonated acetone with the ketone enolate was higher than
that with the ester enolate (17.4 kcal mol¹1 vs. 11.2 kcal mol¹1).
18 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A.
Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S.
Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick,
A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q.
Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03
(Revision D.01), Gaussian, Inc., Wallingford CT, 2004.
8
9
Ketone 1a (1.0 mmol) was added to a CH2Cl2 (2 mL)
suspension of Sn-Mont (20 mg) which had been activated
under vacuum at 120 °C for 1 h, then ketone enolate 2a
(1.1 mmol) was added. The mixture was stirred at 0 °C under
a nitrogen atmosphere. After the reaction was completed, the
catalyst was filtered off and washed with cold CH2Cl2. The
product yields were determined by 1H NMR analysis of the
filtrate using mesitylene as the internal standard.
Catalyzed by homogeneous catalysts: a) W. Odenkirk, J.
G. Onodera, T. Toeda, N.-n. Toda, D. Shibagishi, R. Takeuchi,
© 2014 The Chemical Society of Japan