1
564
M. Kokubo, S. Kobayashi
CLUSTER
silicon enolates 1aa and 1ab in moderate yields, and again Acknowledgment
1
aa gave a better yield. In this case, the fluoride ions can
This work was partially supported by a Grant-in-Aid for Scientific
Research from the Japan Society of the Promotion of Sciences
function as a Lewis base, which could activate both sili-
con enolates to react with aqueous HCHO. When the re-
action was conducted with HF, the yields were low in both
cases (entry 5). Fluoride ions could activate silicon eno-
lates and the proton could activate formaldehyde in these
reactions; however, the proton also decomposed the sili-
con enolates due to its high acidity, leading to the low
yields. From these results, it was revealed that ScF has
unique reactivity in the hydroxymethylation reactions in
aqueous media. The ScF -catalyzed reactions were found
(
JSPS).
References and Notes
(1) (a) Li, C.-J.; Chan, T.-H. Organic Reactions in Aqueous
Media; John Wiley & Sons: New York, 1997. (b) Organic
Synthesis in Water; Grieco, P. A., Ed.; Blackie Academic
and Professional: London, 1998. (c) Lindström, U. M.
Chem. Rev. 2002, 102, 2751. (d) Li, C.-J. Chem. Rev. 2005,
3
3
105, 3095. (e) Pirrung, M. C. Chem. Eur. J. 2006, 12, 1312.
to be different from Lewis acid or fluoride ion catalyzed
reactions. It is noteworthy that reactivity toward TMS and
DMS enolates is different from that in conventional Lewis
(
(
f) Kobayashi, S.; Ogawa, C. Chem. Eur. J. 2006, 12, 5954.
g) Kobayashi, S.; Ogawa, C. Asymmetric Synthesis: The
Essentials, 2nd ed.; Christmann, M.; Bräse, S., Eds.; Wiley-
VCH: Weinheim, 2007, 117. (h) Kobayashi, S. Pure Appl.
Chem. 2007, 79, 235.
acid or fluoride ion catalyzed reactions. ScF could acti-
3
vate DMS enolates preferentially and work as a novel cat-
alyst for hydroxymethylation of DMS enolates in aqueous
media.
(
2) (a) Kobayashi, S. Chem. Lett. 1991, 20, 2187.
(
b) Kobayashi, S.; Hachiya, I. J. Org. Chem. 1994, 59, 3590.
(c) Ishikawa, S.; Hamada, T.; Manabe, K.; Kobayashi, S.
J. Am. Chem. Soc. 2004, 126, 12236. (d) Kobayashi, S.;
Ogino, T.; Shimizu, H.; Ishikawa, S.; Hamada, T.; Manabe,
K. Org. Lett. 2005, 7, 4729. (e) Manabe, K.; Ishikawa, S.;
Hamada, T.; Kobayashi, S. Tetrahedron 2003, 59, 10439.
Table 4 Hydroxymethylation of Silicon Enolates with Various Cat-
alysts
OSiR3
O
Catalyst
(f) Ozasa, N.; Wadamoto, M.; Ishihara, K.; Yamamoto, H.
HCHO
+
Ph
Ph
OH
THF–H2O = 9:1
Synlett 2003, 2219. (g) Torii, H.; Nakadai, M.; Ishihara, K.;
Saito, S.; Yamamoto, H. Angew. Chem. Int. Ed. 2004, 43,
1a
0.5 M, r.t., 17 h
(
5 equiv)
1aa: R3 = Me3
2a
1983. (h) Casas, J.; Sundén, H.; Córdova, A. Tetrahedron
1ab: R3 = Me2H
Lett. 2004, 45, 6117; and references therein.
(
(
3) (a) Kobayashi, S. Synlett 1994, 689. (b) Kobayashi, S. Eur.
J. Org. Chem. 1999, 15. (c) Kobayashi, S.; Sugiura, M.;
Kitagawa, H.; Lam, W. W.-L. Chem. Rev. 2002, 102, 2227.
Entry Catalyst (mol%)
Yield (%)a
1
aa
1ab
4) ScF is commercially available. To the best of our
3
1
2
3
4
none
2
24
81
41
51
13
knowledge, ScF was previously used in one stoichiometric
3
reaction: Kauffmann, T.; Pahde, C.; Tannert, A.;
Wingbermühle, D. Tetrahedron Lett. 1985, 26, 4063.
ScF (20)
trace
69
3
(
5) Quite recently, we found a unique characteristic of ZnF as a
2
ScCl ⋅6H O (20)
3
2
catalyst in aqueous media: (a) Hamada, T.; Manabe, K.;
Kobayashi, S. Angew. Chem. Int. Ed. 2003, 42, 3927.
KF (20) + 18-crown-6 (20)
HF (20)
63
(
b) Fujita, M.; Nagano, T.; Schneider, U.; Ogawa, C.;
5
14
Kobayashi, S. unpublished results.
(
(
(
6) A commercially available HCHO solution including 5–10%
MeOH stabilizer was used.
7) Miura, K.; Nakagawa, T.; Hosomi, A. J. Am. Chem. Soc.
a
Isolated yield.
2002, 124, 536.
In conclusion, we have revealed that ScF is a novel cata-
lyst for the hydroxymethylation reaction of DMS enolates
with aqueous HCHO. The present study shows the first
example of ScF -catalyzed organic reactions. It should be
3
8) For fluoride ion catalyzed reactions, see: (a) Noyori, R.;
Nishida, I.; Sakata, J. J. Am. Chem. Soc. 1983, 105, 1598.
9
(
b) Nakamura, E.; Shimizu, M.; Kuwajima, I.; Sakata, J.;
3
Yokoyama, K.; Noyori, R. J. Org. Chem. 1983, 48, 932.
noted that the reactions proceeded smoothly in aqueous
(9) Typical Procedure for Hydroxymethylation Reactions:
To a solution of ScF (0.03 mmol) in THF–H O (2.7 mL/
media, and that ScF showed unique characteristics com-
3
2
3
0
.22 mL) was added 36% aq solution of formaldehyde (1.5
mmol) and (Z)-dimethyl(1-phenylprop-1-enyloxy)silane
1ab, 0.3 mmol). The reaction mixture was stirred for 40 h at
pared with standard Lewis acid or Lewis base catalysts.
Further investigations to develop new reactions using
(
ScF mainly in aqueous media including asymmetric ca-
3
r.t. The mixture was then diluted with H O (10 mL), and the
2
talysis are now in progress.
aqueous layer was extracted with CH Cl (3 × 20 mL). The
2
2
combined organic extracts were washed with brine, and
dried over anhyd Na SO . After filtration, the solvent was
2
4
removed in vacuo. The residue was purified by preparative
TLC (elution with n-hexane–EtOAc = 3:2) to give 3-
hydroxy-2-methyl-1-phenylpropane-1-ono (2a) in 89%
yield.
Synlett 2008, No. 10, 1562–1564 © Thieme Stuttgart · New York