Table 2 Catalytic asymmetric benzylidenation of various aldehydesa
eeb
(62.9 MHz, C
D
) 18.7, 39.8, 79.1; n 2m ax (KBr)/cm21 2920, 1440, 1370,
6
6
2
D
1
090, 1046, 1030, 1000, 990, 802; [a] +64.4 (c 0.41 in CHCl3); HRMS
+
(EI) m/z calcd. (M 2 Br) 242.9287, found 242.9241.
Yield dr trans (S,S)
‡ Representative experimental procedure: to a solution of selenolane 1
t
Entry
Aldehyde
(%)
(%)
(%)
(0.020 mmol) in a 9+1 mixture of Bu OH and water (0.80 mL) were added
benzyl bromide (48 mL, 0.40 mmol), benzaldehyde (20 mL, 0.20 mmol) and
powdered NaOH (16 mg, 0.40 mmol). The reaction mixture was stirred at
room temperature for 24 h then water was added. The aqueous phase was
1
2
3
4
5
6
7
8
9
Benzaldehyde
4-Tolualdehyde
91
97
97
97
76
66
67
65
72
86
1+1
1+1
1+1
1+1
1+1
1+1
1+1
1+1
1+1
1+1
91
92
92
76
83
94
93
92
94
94
2-Naphthaldehyde
4-Chlorobenzaldehyde
4-Trifluoromethylbenzaldehyde
(E)-Cinnamaldehyde
2-Furaldehyde
extracted with CH
2 2
Cl . The combined organic layers were dried over
MgSO and then concentrated to dryness. Purification by silica gel column
4
chromatography (eluent diethyl ether–ethyl acetate) gave the expected
oxirane. The ee was determined by HPLC analysis on a Daicel Chiralpak
AD column (9+1 n-hexane–propan-2-ol).
c
§ Crystal data for 2: C
P4 2, at 293.2 K, a = 9.009(3), b = 9.009(3), c = 12.21(1) Å, V =
991.0(7) Å 3 , Z = 8, F(000) = 608.00, m(MoKa) = 0.7107 cm , Dcalc
3 6
H BrSe0.5. M = 161.46, tetragonal, space group
2-Thiophenecarboxaldehyde
3 1
2
c
21
10
2
3
a
1 2
= 2.164 g cm , final R values R = 0.0452 (all data), wR = 0.0358.
All reactions were performed with selenolane 1 (0.020 mmol, 20 mol% to
aldehyde), benzyl bromide (0.40 mmol), aldehyde (0.20 mmol) and NaOH
0.40 mmol) at rt for 7 days. Enantiomeric excesses were determined by
chiral HPLC using a Daicel AD column. Reaction time: 4 h.
CCDC 167809. See http://www.rsc.org/suppdata/cc/b1/b106063p/ for elec-
tronic files in .cif or other electronic format.
b
(
c
1
2
A. Krief, in The Chemistry of Organic Selenium and Tellurium
Compounds, ed. S. Patai, New York, 1987, vol. 2, p. 675.
A. Krief, W. Dumont, D. Van Ende, S. Halazy, D. Labar, J.-L.
Laboureur and T. Q. Lê, Heterocycles, 1989, 28, 1203.
These results led us to achieve a catalytic procedure.23–25
Using 0.2 equivalent of selenolane 1 and eight aldehydes, at
ambient temperature for a maximum of 7 days, good to
excellent yields of oxiranes (65–97%) were obtained (Table 2).
For the more reactive heteroaromatic aldehydes (entries 8, 10)
the reaction time could be optimized to 4 h. Enantiomeric
excesses were 91–94% (entries 1–3, 6–10), except for alde-
hydes bearing electron-withdrawing groups (entries 4, 5).
3 W. Dumont, P. Bayet and A. Krief, Angew. Chem., Int. Ed. Engl., 1974,
3, 274.
K. Takaki, M. Yasumura and K. Negoro, Angew. Chem., Int. Ed. Engl.,
981, 20, 671.
1
4
5
6
1
C. Paulmier, Selenium Reagents and Intermediates in Organic Synthe-
sis, Pergamon Press, Oxford, 1986.
T. Wirth, Tetrahedron, 1999, 55, 1.
7 T. Kawashima and R. Okazaki, Synlett, 1996, 600.
8 A.-H. Li, L.-X. Dai and V. K. Aggarwal, Chem. Rev., 1997, 97, 2341.
9 F. Volatron and O. Eisenstein, J. Am. Chem. Soc., 1987, 109, 1.
10 M. K. Lindvall and A. M. P. Koskinen, J. Org. Chem., 1999, 64,
4596.
1
3,14
As compared to the sulfur analogues,
this series leads to
enhanced reactivity and higher asymmetric induction, with the
same absolute configuration.
26
Another feature is the diastereoselectivity, which has
almost not been addressed so far in the selenium series.1,2 Under
11 E. Maccarone and G. Perrini, J. Chem. Soc., Perkin Trans. 2, 1983,
1
605.
2 W. von E. Doering and A. K. Hoffmann, J. Am. Chem. Soc., 1955, 77,
21.
3 K. Julienne, P. Metzner, V. Henryon and A. Greiner, J. Org. Chem.,
998, 63, 4532.
stoichiometric conditions, the trans oxirane was the major
isomer but to a much lesser extent than with sulfides (for the
example of benzaldehyde: excess of 18–34% instead of 86%).
The catalytic series provides an equal abundance of trans and
cis oxiranes, for most cases. This trend towards the cis isomer is
reminiscent of the reaction of unstabilized sulfur ylides with
aliphatic aldehydes, and of the Wittig reaction of unstabilized
phosphoranes with aldehydes. The higher reactivity observed
here with selenonium ylides leads us to propose early transition
states, and possible hypervalent oxaselenetane intermedi-
ates.7
1
1
5
1
14 K. Julienne, P. Metzner and V. Henryon, J. Chem. Soc., Perkin Trans.
1, 1999, 731.
15 J. A. Gladysz, J. L. Hornby and J. E. Garbe, J. Org. Chem., 1978, 43,
1
204.
1
1
1
6 E. Honda, T. Iwamura, S.-i. Watanabe, T. Kataoka, O. Muraoka and G.
Tanabe, J. Chem. Soc., Perkin Trans. 1, 2001, 529.
7 L. J. Benjamin, C. H. Schiesser and K. Sutej, Tetrahedron, 1993, 49,
,27
2
557.
In conclusion this first report of chiral selenium ylides
demonstrates that they can provide efficient asymmetric
induction for the synthesis of epoxides. They exhibit marked
differences with sulfur ylides. The catalytic version is com-
8 G. T. Morgan and F. H. Burstall, J. Chem. Soc., 1929, 1096.
19 N. Furukawa and S. Sato, in Chemistry of Hypervalent Compounds, ed.
K.-y. Akiba, New York, 1999, p. 241.
20 E. L. Muetterties and R. A. Schunn, Quart. Rev., 1966, 20, 245.
21 J. D. McCullough and R. E. Marsh, Acta Crystallogr., 1950, 3, 41.
petitive with previous methods in the sulfur series.2
3–25,28–30
2
2 J. D. McCullough and G. Hamburger, J. Am. Chem. Soc., 1941, 63,
03.
We thank CNRS and PunchOrga (‘Réseau inter-régional du
Pôle Universitaire Normand de Chimie Organique’) for sup-
port.
8
2
2
3 V. K. Aggarwal, Synlett, 1998, 329.
4 V. K. Aggarwal, in Comprehensive Asymmetric Catalysis, ed. E.
Jacobsen, A. Pfaltz and H. Yamamoto, Berlin, 1999, vol. 2, p. 679.
5 J. Zanardi, C. Leriverend, D. Aubert, K. Julienne and P. Metzner, J. Org.
Chem., 2001, 66, 5620.
2
Notes and references
†
Experimental data for 1: pale yellow oil; d
H
(250 MHz, CDCl
3
) 1.45 (6H,
26 V. K. Aggarwal, S. Calamai and G. J. Ford, J. Chem. Soc., Perkin Trans.
1, 1997, 593.
27 F. Ohno, T. Kawashima and R. Okazaki, Chem. Commun., 1997,
1671.
28 V. K. Aggarwal, E. Alonso, G. Hynd, K. M. Lydon, M. J. Palmer, M.
Porcelloni and J. R. Studley, Angew. Chem., Int. Ed., 2001, 40, 1430.
29 R. Hayakawa and M. Shimizu, Synlett, 1999, 1328.
30 T. Saito, D. Akiba, M. Sakairi and S. Kanazawa, Tetrahedron Lett.,
2001, 42, 57.
d, J 6.6 Hz, 2 Me), 1.57–1.63 (2H, m), 2.25–2.30 (2H, m), 3.77–3.85 (2H,
2
1
m, 2 CH); d
C
(62.9 MHz, CDCl3) 21.3, 38.2, 39.3; nmax (NaCl)/cm 2966,
2
2
2
950, 2920, 1090, 1046, 1030, 1000, 990, 802; [a]D +166 (c 1.31 in
CHCl
3
); HRMS (EI) m/z calcd. 164.0104, found 164.0131. 2: yellow
(250 MHz, CDCl ) 1.83 (6H, d, J 6.9 Hz, 2
Me), 2.29–2.36 (m, 2H), 2.67–2.76 (m, 2H), 4.85–4.93 (m, 2H); d (250
MHz, C ) 1.49 (6H, d, J = 6.6 Hz, 2 Me), 1.65–1.71 (m, 2H), 1.96–2.04
m, 2H), 4.40–4.47 (m, 2H); d (62.9 MHz, CDCl ) 20.1, 39.4, 78.7; d
needles; mp 93.5–94.5 °C; d
H
3
H
6 6
D
(
C
3
C
Chem. Commun., 2001, 2350–2351
2351