632
K. Matsumoto, K. Tomioka / Tetrahedron Letters 43 (2002) 631–633
Table 1. Asymmetric epoxidation of olefins with ketone–
hexene 10f using 3 in a mixture of 1,4-dioxane and
water (3:2) at −8°C to give 11f in 82% ee (run 15).
Oxone®
R3
It is noteworthy that the catalytic epoxidation of 10f
with substoichiometric amount of 1 and 3 in MeCN–
DMM–water gave 11f in a reasonably high enantiose-
lectivity. The reaction with 40 mol% of 1 and 3 at rt for
2 h gave quantitatively 11f in 71 and 76% ee, respec-
tively. It was remarkable to find that the reaction with
20 mol% of 3 at −12°C for 4 h gave 11f in 83% ee and
quantitative yield.
R3
1-3, Oxone, rt
O
R4
11
R4
R5
MeCN-DMM,
aq EDTA, Bu4NHSO5
R5
10
R3
R4
R5
10
a
Run
Ee %
Confgn
1-3 Time h Yield %
S,S
R,R
R,R
S,S
R,R
S,S
R,R
S
Ph
H
Ph
57
6
1
2
3
1
3
1
3
1
3
1
3
1
3
1
3
2
2
2
3
2
2
2
5
6
2
2
2
2
2
2
99
40
93
41
24
52
78
63
48
99
99
99
99
99
99
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
64
18
27
57
62
70
73
75
61
71
75
78
82
b
c
d
e
f
C6H13H
C6H13
CH3
Ph
Acknowledgements
Ph
Ph
H
This research was supported by a Grant-in-Aid for
Scientific Research on Priority Areas (A) ‘Exploitation
of Multi-Element Cyclic Molecules’ from the Ministry
of Education, Culture, Sports, Science and Technology,
Japan.
Ph
R
1R,2S
1S,2R
S,S
R,R
S,S
R,R
References
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Run 14,15; A mixture of 1,4–
dioxane and water was used
as a solvent at –8°C.
10f
10e
in only 6% ee (Table 1, runs 1 and 2). It was surprising
to know that the diphenyl steric wall of 2 was not
effective and 1 behaved favorably more than 2. Since
the more vacant space seems to be available in the
bottom side of A rather than the top side, there should
be some factors other than steric, which control the
stereoselection in the bottom side. The conformational
difference between A and B was assumed to be respon-
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atoms of A produce Coulomb repulsion with the phenyl
ring of stilbene more effectively than those of B. Poorer
selectivity, 18% ee, in the reaction of trans-olefin 10b
bearing alkyl substituents at the both olefin terminal
agreed with the assumption (run 4). Based on both the
electronic wall hypothesis above and an advantageous
motif C2 symmetry, we designed and prepared a ketone
3 starting from 910 via 6 (Figs. 1 and 2). Epoxidation of
10a with 3 provided 11a11 in 66% ee (run 3).
The alkyl substituent at one end was not an obstacle
allowing epoxidation of 10c in 57% ee (run 6). Epoxida-
tion of linear trans-di 10a–c (runs 1–7), tri-substituted
10d (runs 8 and 9), and cyclic 10e and 10f (runs 10–13)
olefins was examined with 2 equiv. of 1 or 3 in acetoni-
trile–DMM at room temperature. The sense of enantio-
facial selection was the same, top face attack to 10 for
1, and bottom face attack for 3 of the reversed-type of
absolute configuration to 1. Generally, C2 symmetric
ketone 3 behaved in a better way than 2. The best ee
value was obtained by the reaction of 1-phenylcyclo-
4. For a recent review on asymmetric epoxidation of elec-
tron-deficient olefins, see: Porter, M. J.; Skidmore, J.
Chem. Commun. 2000, 1215.
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