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K. Matsui et al. / Tetrahedron Letters 46(2005) 1943–1946
1945
Table 2. Enantioselective MBH reaction of 1 with 2 promoted by boron-lithium-mono(binaphthoxide) (type B BLB) in the presence of (n-Bu)3Pa
(R)-type B BLB (16 mol %)
(n-Bu)3P (10 mol %)
O
O
OH
O
+
R
H
R
( )n
( )n
THF
1
2
3
Entry
n = 1 or 2
R
Temp (°C)
Time (h)
Product
Yield (%)
Ee (%)b
1
1a (n = 1)
1b (n = 2)
PhCH2CH2 (2a)
2a
ꢀ40
0
120
240
288
288
288
3.5
3a
3b
3c
3d
3e
3f
70
49
23
94
42
93
32
60
88
71
64
58
85
99
97
19
15
52
93
63
2
3
1b
1b
1a
1a
1b
1b
1a
1b
Et (2b)
i-Pr (2c)
t-Bu (2d)
Ph (2e)
2e
0
4c
5c
6
0
ꢀ40
rt
7
0
120
240
168
48
3g
3h
3i
8
C5H9 (2f)
C6H11 (2g)
2g
rt
9c
10
ꢀ40
rt
3j
a Reactions were carried out using type B BLB (0.08 mmol), 1 (41.9 lL, 0.5 mmol), 2 (98.8 lL, 0.75 mmol) and (n-Bu)3P (12.5 lL, 0.05 mmol).
b The enantiomeric excess of the adduct was determined by chiral stationary phase HPLC analysis (3a,f,g: Daicel Chiralpak AS column, 3b: Daicel
Chiralcel OD column, 3c–e,h,j: Daicel Chiralpak AS-H column, 3i: Daicel Chiralcel OD-H column;detection: 3a,b,f,g: 254 nm, 3c–e,h–j: 226 nm;
eluent: hexane/2-PrOH = 9). The (S)-configuration was determined by optical rotation of purified products.
c 2.5 mmol of 2 was used.
O
References and notes
O
s-Bu
s-Bu
OH
O
O
B
Li
*
(n-Bu) P +
Ph
3
*
3a
1. For recent reviews, see: (a) Basavaiah, D.;Rao, P. D.;
Hyma, R. S. Tetrahedron 1996, 52, 8001–8062;(b)
Ciganek, E. Org. React. 1997, 51, 201–350;(c) Langer,
P. Angew. Chem. Int. Ed. 2000, 39, 3049–3052;(d)
type B BLB
1a
O
O
s-Bu
s-Bu
OH
Basavaiah, D.;Rao, A. J.;Satyanarayana, T.
Rev. 2003, 103, 811–891.
Chem.
O
s-Bu
s-Bu
B
*
B
*
*
OH
BINOL
O
Li
O
O
Li
O
2. (a) Bailey, M.;Staton, I.;Ashton, P. R.;Marko, I. E.;
Ollis, W. D. Tetrahedron: Asymmetry 1991, 2, 495–509;(b)
Brzezinski, L. J.;Rafel, S.;Leahy, J. W. Tetrahedron 1997,
53, 16423–16434;(c) Iwabuchi, Y.;Furukawa, M.;Esumi,
T.;Hatakeyama, S. Chem. Commun. 2001, 2030–2031;(d)
Frank, S. A.;Mergott, D. J.;Roush, W. R. J. Am. Chem.
Soc. 2002, 124, 2404–2405.
(n-Bu) P
3
Ph
P(n-Bu)
3
O
s-Bu
s-Bu
B
*
O
H
O
Li
O
Ph
3. (a) Yang, K. S.;Lee, W. D.;Pan, J. F.;Chen, K. J. Org.
Chem. 2003, 68, 915–919;(b) Walsh, L. M.;Winn, C. L.;
Goodman, J. M. Tetrahedron Lett. 2002, 43, 8219–8222;
(c) Yamada, Y. M. A.;Ikegami, S. Tetrahedron Lett. 2000,
41, 2165–2169;(d) McDougal, N. T.;Schaus, S. E. J. Am.
Chem. Soc. 2003, 125, 12094–12095;(e) Barrett, A. G. M.;
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2534;(f) Iwabuchi, Y.;Nakatani, M.;Yokoyama, N.;
Hatakeyama, S. J. Am. Chem. Soc. 1999, 121, 10219–
10220;(g) Shi, M.;Jiang, J. K. Tetrahedron: Asymmetry
2002, 13, 1941–1947;(h) Mocquet, C. M.;Warriner, S. L.
Synlett 2003, 356–358;(i) Hayase, T.;Shibata, T.;Soai,
K.;Wakatsuiki, Y. Chem. Commun. 1998, 1271–1272;(j)
Imbriglio, J. E.;Vasbinder, M. M.;Miller, S. J. Org. Lett.
2003, 5, 3741–3743;(k) Krishna, P. R.;Kannan, V.;
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2a
P(n-Bu)
3
Scheme 1. Proposed mechanism of MBH reaction promoted by
heterobimetallic catalyst with (n-Bu)3P.
mechanism of this MBH reaction promoted by heterobi-
metallic catalyst with (n-Bu)3P is shown in Scheme 1.
In conclusion, asymmetric catalysis using a combination
of a heterobimetallic complex and (n-Bu)3P was found
to accelerate the enantioselective MBH reaction to af-
ford the adduct in good chemical yield with moderate
to high enantioselectivity. Further studies aimed at elu-
cidating the structure of the catalysts and the mecha-
nism of double activation are currently in progress.
Vo-Thanh, G.;Gori, D.;Loupy, A.
2004, 45, 6425–6428.
Tetrahedron Lett.
4. Itoh, K.;Kanemasa, S. J. Am. Chem. Soc. 2002, 124,
13394–13395.
5. Shibasaki, M.;Sasai, H.;Arai, T. Angew. Chem. Int. Ed.
Engl. 1997, 36, 1236–1256.
Acknowledgements
The authors thank the technical staff of the ISIR Mate-
rials Analysis Center. This work was supported by the
Ministry of Education, Science, Sports and Culture,
Japan.
6. (a) Shi, M.;Xu, Y. M. Chem. Commun. 2001, 1876–1877;
(b) Rafel, S.;Leahy, J. M. J. Org. Chem. 1997, 62, 1521–
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