concentrated under reduced pressure. The residue was purified
by silica gel column chromatography using hexane–ethyl acetate
(5:1) to give dimethyl 1-methyl-1λ4-selenabenzene-2,6-dicarb-
oxylate (9a) (203 mg, 74%), dark red oil (Found: C, 43.6; H, 4.4;
C10H12O4Se requires C, 43.48; H, 4.35%); νmax(film)/cmϪ1 1660
Y
Y
R
R
9
Se
Me
10
X
COC6H4Br(p)
O
O
Me
(ester C᎐O); δ (400 MHz; CDCl3) 2.14 (3 H, s, SeMe), 5.23
᎐
H
(1 H, t, J 9, 4-H), 3.80 (6 H, s, OMe × 2), 7.39 (2 H, t, J 9, 3- and
5-H); δC (100 MHz; CDCl3) 26.6 (q), 52.0 (q), 83.4 (s), 101.0 (d),
139.2 (d), 165.8 (s); δSe (76 MHz; CDCl3) 310; m/z (EI) 276 (Mϩ,
10%), 261 (100).
11; X=S, Y=H
12; X=Se, Y=Me
R
Diethyl 2-methyl-2H-selenine-2,6-dicarboxylate 13
ROC
Se
COR
ROC
Se
COR
ROC
Se
Yellow oil; νmax(film)/cmϪ1 1720 (ester C᎐O); δ (400 MHz;
Me
A
Me
B
Me
C
O
᎐
H
CDCl3) 1.30 (3 H, t, J 7, CH2CH3), 1.33 (3 H, t, J 7, CH2CH3),
1.71 (3 H, s, SeMe), 4.24 (2 H, q, J 7, CH2CH3), 4.28 (2 H, q,
J 7, CH2CH3), 5.93 (1 H, d, J 11, 3-H), 6.17 (1 H, dd, J 7 and 11,
4-H), 7.36 (1 H, d, J 7, 5-H); δC (100 MHz; CDCl3) 13.9 (q),
14.1 (q), 26.6 (q), 44.1 (s), 61.5 (t), 62.1 (t), 124.7 (s), 125.4 (d),
128.1 (d), 129.0 (d), 165.1 (s), 172.4 (s); δSe (76 MHz; CDCl3)
350; m/z (EI) 304.0217 (C12H16O4Se requires 304.0213), 304
(Mϩ, 10%), 231 (100).
Fig. 1
Me
benzene
Me
9b
reflux, 2.5 h
EtO2C
Se
EtO2C
Se
CO2Et
CO2Et
13
14
Compound 13 was isolated.
Diethyl 4-methyl-4H-selenine-2,6-dicarboxylate 14
O
δH (400 MHz; CDCl3) 1.33 (6 H, t, J 7, CH2CH3), 1.33 (3 H, d,
J 7, Me), 3.23 (1 H, tq, J 4 and 7, 4-H), 4.28 (4 H, q, J 7,
CH2CH3), 6.94 (2 H, d, J 4, 3- and 5-H); δC (100 MHz; CDCl3)
14.1 (q), 19.0 (q), 35.7 (d), 61.7 (t), 123.9 (s), 136.9 (d), 163.9 (s).
These data were picked up from the NMR spectra of a mixture
of 13 and 14.
MeSe
PhOC
O
OMe
COPh PhOC
O2/ MeOH
rt, 1 week
9c
Se
COPh
16
15
Scheme 2
1,5-dibenzoyl-1-methoxy-5-methylselenopenta-1,4-dien-3-one
15 (20%) and 1,5-dibenzoyl-4H-selenin-4-one 16 (36%). The
dienone 15 and the selenin-4-one 16 would be produced by
oxygenation of C(4) of 9c and the subsequent cleavage of
the C(1)–Se bond or the subsequent demethylation of the
Se–methyl group, respectively, due to attack of methanol. In the
1H NMR spectrum of 15, the two olefinic signals, the H(2) and
H(4) signals, appeared at δ 5.70 and 7.24 and the two methyl
signals, the SeMe and OMe signals, appeared at δ 1.88 and 3.81.
In the 13C NMR spectrum of 15, four olefinic carbon signals
and three carbonyl signals were observed. These NMR spectral
data and other analytical data supported the structure of 15. A
nuclear Overhauser effect (NOE) enhancement was observed
between the H(2) signal at δ 5.70 and the doublet signal at δ 7.95
due to H(2Ј,6Ј) of the 1-benzoyl group and between the H(4)
signal at δ 7.24 and the doublet signal at δ 8.04 due to H(2Ј,6Ј)
of the 5-benzoyl group. This indicates that the geometry of 15
is the (Z,Z) configuration. The preparation of 9a and reactions
of 9b, c are given as an example. Further study of the
selenabenzenes 9a–c will be described in a full paper.
(Z,Z)-1,5-Dibenzoyl-1-methoxy-5-methylselenopenta-1,4-dien-
3-one 15
Red oil; νmax(film)/cmϪ1 1660, 1620, 1600 (C᎐O); δ (400 MHz;
᎐
CDCl3) 1.88 (3 H, s, SeMe), 3.81 (3 H, s, OMe), H5.70 (1 H, s,
2-H), 7.24 (1 H, s, 4-H), 7.50–7.53 (4 H, m, aromatic), 7.63–7.65
(2 H, m, aromatic), 7.95 (2 H, d, J 7, aromatic), 8.04 (2 H, d, J 7,
aromatic); δC (100 MHz; CDCl3) 6.6 (q), 59.5 (q), 112.6 (d),
123.7 (d), 128.9 (d), 129.0 (d), 129.9 (d), 134.4 (d), 134.5 (d),
135.2 (s), 158.5 (s), 160.4 (s), 186.3 (s), 191.6 (s), 193.1 (s); δSe
(76 MHz; CDCl3) 379; m/z (EI) 414.0359 (C21H18O4Se requires
414.0370), 314 (Mϩ, 6%), 105 (100).
2,6-Dibenzoyl-4H-selenin-4-one 16
Colorless needles, mp 145–156 ЊC (from methanol) (Found: C,
62.1; H, 3.2; C19H12O3Se requires C, 62.1; H, 3.3%); νmax(KBr)/
cmϪ1 1610, 1650 (C᎐O); δ (400 MHz; CDCl ) 7.55 (4 H, t, J 7,
᎐
3
aromatic), 7.56 (2 H, s, 3-Hand 5-H), 7.69 (2 H, t, J 7, aromatic),
7.83 (4 H, d, J 7, aromatic); δC (100 MHz; CDCl3) 129.0 (d),
129.9 (d), 134.0 (s), 134.4 (s), 136.4 (d), 136.5 (d), 154.3 (s),
193.3 (s); δSe (76 MHz; CDCl3) 462; m/z (EI) 368 (Mϩ, 25%),
105 (100).
Experimental
Synthesis of dimethyl 1-methyl-1ë4-selenabenzene-2,6-dicarb-
oxylate (9a)
References
1 M. Hori, T. Kataoka, H. Shimizu, K. Tsutsumi and S. Imaoka,
Heterocycles, 1987, 26, 2365.
2 M. Hori, T. Kataoka, H. Shimizu, K. Tsutsumi and M. Yoshimatsu,
Heterocycles, 1990, 30, 295; M. Hori, T. Kataoka, H. Shimizu,
K. Tsutsumi and M. Yoshimatsu, J. Org. Chem., 1990, 55, 2458.
3 T. Kataoka, Y. Ohe, A. Umeda, T. Iwamura, M. Yoshimatsu and
H. Shimizu, Chem. Pharm. Bull., 1994, 42, 811.
4 T. Imamoto, H. Yokoyama and M. Yokoyama, Tetrahedron Lett.,
1981, 22, 1803; T. Imamoto, M. Matsumoto, H. Yokoyama,
M. Yokoyama and K. Yamaguti, J. Org. Chem., 1984, 49, 1105.
5 H. Shimizu, N. Kudo, T. Kataoka and M. Hori, Tetrahedron Lett.,
31, 1990, 115.
A mixture of dimethyl 4H-selenine-2,6-dicarboxylate 6a (261
mg, 1 mmol), iodomethane (0.4 cm3, 6 mmol) and silver tetra-
fluoroborate (324 mg, 1.5 mmol) in dichloromethane (15 cm3)
was stirred for 2 h at 0 ЊC. The precipitate was filtered off and
washed with dichloromethane. The filtrate and the washing
were combined and concentrated to dryness. Triethylamine
(0.6 cm3, 4 mmol) was added to a solution of the residue, a
mixture of 1-methyl-2,6-bis(methoxycarbonyl)-4H-seleninium
tetrafluoroborate (7a) and 1-methyl-2,6-bis(methoxycarbonyl)-
2H-seleninium tetrafluoroborate (8a), in ethanol (15 cm3) at
0 ЊC with stirring. The reaction mixture was stirred for 5 h at 0
ЊC and then water was added to it. The whole was extracted
with dichloromethane. The extracts were dried (MgSO4) and
Communication 9/01467E
1156
J. Chem. Soc., Perkin Trans. 1, 1999, 1155–1156