6
96
JIANG CHENGJUN
00
1
50
40
30
20
10
80
60
40
20
1
st nm
1
st nm
2nd nm
nd nm
2nd nm
3nd nm
3
0
50
100
Time, min
150
200
0
20 40 60 80 100 120 140 160 180 200
Time, min
Fig. 5. Recycling (salen)Co(III)ꢀOAc + (salen)Co–AlCl (equimolar amounts). Reaction conditions: amounts of
1
and 2d
—
3
0.0025 mol (0.25 mol %), (
±
)ꢀepichlorohydrin—1 mol, water—0.55 mol, chlorobenzene as internal standard (12 ml), temperꢀ
ature 298 K.
1
0 (see the table), 1,2ꢀdiols and epoxy compounds also be used as a general catalyst for the asymmetric
were synthesized in relatively poor yield and optical ring opening of terminal epoxide with H O and other
2
purity. It is noteworthy that ee values in entries 1–10 nucleophiles.
are 2–3% smaller than at the ratio of 1 : 1.
Authors are grateful to the Zhejiang University of
Science and Technology Research Grant for the supꢀ
port of this work.
The identity of the counterions in the catalysts was
revealed to be a critical parameter for attainment of high
enantioselectivity and reaction rates. (Salen)Co(III)ꢀ
OAc and (salen)Co–ZnCl or (salen)Co–FeCl proved
2
3
REFERENCES
superiority relative to (salen)Co–SnCl or (salen)Co–
4
1
. Jiang, C.J. and Chen, Z.R., Kinet. Catal., 2008, vol. 49,
p. 447.
AlCl in the kinetic resolution of terminal epoxides. They
3
were found to display activity in the HKR of terminal
epoxides about two times in comparison with (salen)
Co(III)ꢀOAc used alone.
2. Ready, J.M. and Jacobsen, E.N., J. Am. Chem. Soc.
001, vol. 123, p. 2687.
,
2
3
4
5
. Tokunaga, M., Larrow, J.F., Kakiuchi, F., and Jacobꢀ
sen, E.N., Science, 1997, vol. 277, p. 936.
The results of entries 11–16 with propylene oxide
highlight the practical aspects of reactions using
. Furrow, M.E., Schaus, S.E., and Jacobsen, E.N.,
J. Org. Chem., 1998, vol. 63, p. 6776.
(
(
salen)Co(III)ꢀOAc and (salen)Co–ZnCl2 or
salen)Co(FeCl ) catalyst to provide recovered
3
. Nielson, L.P.C., Stevenson, C.P., Backmond, D.G.,
and Jacobsen, E.N., J. Am. Chem. Soc., 2004, vol. 126,
p. 1360.
epoxide ee 98–99% and diol ee 95–96%.
As demonstrated the data in entries 17–22, styrene
oxide and styrenediol were obtained with high yield
and enantiomeric excess of epoxide and diol after 3 h
using 0.25 mol % Co was 90–99% and 89–96%,
respectively.
6. Kawthekar, R.B., Bi, W.T., and Kim, G.J., Appl. Orgaꢀ
nomet. Chem., 2008, vol. 22, p. 583.
7. Song, Y.M., Yao, X.Q., Chen, H.L., Bai, C.M.,
Hu, X.Q., and Zheng, Z., Tetrahedron Lett., 2002,
vol. 43, p. 6625.
The use of tetrahydrofurane in the HKR of epoxides
offers the advantage in comparison with CH Cl or withꢀ
8
. Aertsa, S., Buekenhoudta, A., Weytena, H., Vankeleꢀ
comb, I.F.J., and Jacobs, P.A., Tetrahedron: Asymmetry
005, vol. 16, p. 657.
2
2
,
out solvent (cp. entries 11 and 15, 16; 20, 21 and 22).
2
So, the HKR provides straightforward and one pot
synthesis of chiral building blocks. The catalyst can be
9. Jiang, C.J. and Chen, Z.R., Prog. Chem., 2008, vol. 20,
p. 1294.
synthesized easily and recycled up to three cycles withꢀ 10. Jain, S., Zheng, X.L., and Jones, C.W., Inorg. Chem.
,
out noticeable loss in enantioselectivity. Using
equimolar amounts of bimetallic chiral (salen)Co and
2007, vol. 46, p. 8887.
1
1
1
1. Jain, S., Venkatasubbaiah, K., Jones, C.W., and
(
salen)Co(III)ꢀOAc increases the catalytic activity
Davis, R.J., J. Mol. Catal. A: Chem., 2010, vol. 316, p. 8.
more than two times relative to (salen)Co(III)ꢀOAc
used alone. Catalytic system can be recycled and
reused for three runs without any significant loss of
catalytic activity. It is expected that this catalyst can
2. Sun, K.J., Li, W.X., Feng, Z.C., and Li, C., Chem.
Phys. Lett., 2009, vol. 470, p. 259.
3. Jiang, C.J., Dissertation, Zhejiang, China: Zhejiang
Univ. 2009.
KINETICS AND CATALYSIS Vol. 52
No. 5
2011