164.8; 77Se NMR (95 MHz, CD3OD) δ 1230; UV (propan-2-ol):
λmax 253 (ε 1.28 × 104), 200 (ε 2.14 × 104) nm; MS (EI) m/z 221
(80Se, Mϩ ϩ 1), 219 (78Se, Mϩ ϩ 1), 186, 184.
1.52 (s, 9H), 2.42 (br, 1H), 4.08 (s, 3H), 7.00 (d, 1H, J = 1.6 Hz),
7.14 (d, 1H, J = 1.6 Hz); 13C NMR (125 MHz, CDCl3) δ 31.1,
33.3, 35.6, 36.9, 57.8, 110.3, 117.1, 133.6, 150.8, 156.4, 160.4;
77Se NMR (95 MHz, CDCl3) δ 1213; IR (KBr) νmax 3220 (br),
2-Methoxybenzeneseleninic acid (3)21
2961, 2362, 1591, 1559, 1405, 1302, 1240, 1057, 847, 661 cmϪ1
;
UV (hexane–propan-2-ol = 95 : 5): λmax 294 (ε 4.65 × 103), 242
(sh, ε 7.06 × 103), 212 (ε 2.26 × 104) nm; MS (EI) m/z 316 (80Se,
Mϩ Ϫ 16), 314 (78Se, Mϩ Ϫ 16), 298, 296, 187, 71. Anal. Calcd
for C15H24O3Se: C, 54.38; H, 7.30. Found: C, 54.73; H, 7.35%.
1
Mp 132–134 ЊC; H NMR (500 MHz, CDCl3) δ 3.92 (s, 3H),
6.20 (br, 1H), 6.97 (d, 1H, J = 8.2 Hz), 7.17 (dd, 1H, J = 7.5, 7.5
Hz), 7.52 (dd, 1H, J = 7.5, 8.2 Hz), 8.01 (d, 1H, J = 7.5 Hz); 13
C
NMR (125 MHz, CDCl3) δ 56.2, 111.4, 121.7, 126.5, 134.2
(duplicate), 158.2; 77Se NMR (95 MHz, CD3OD) δ 1210; UV
(propan-2-ol): λmax 290 (ε 4.03 × 103), 233 (ε 6.01 × 103), 206
(ε 2.48 × 104) nm; MS (EI) m/z 219 (80Se, Mϩ Ϫ 1), 217 (78Se,
Mϩ Ϫ 1), 202, 200, 185, 183, 107, 77.
Typical procedure for optical resolution of areneseleninic acids
Racemic areneseleninic acid (50 mg) in eluent (0.3 mL) was
charged to a chiral column packed with amylose carbamate
derivative–silica gel (Daicel Chiralpak AS; 10 × 250 mm) and
eluted with propan-2-ol (for 1, 3, and 4) or hexane containing
50 (for 2), 10 (for 5), 5 (for 9), 2 (for 6), 1 (for 7), and 0.5 (for 8)
vol% propan-2-ol at a flow rate of 1.0 mL minϪ1. About each
15 mg of optically active areneseleninic acid was collected as
eluates from the fastest eluted portion and next portion, and
the specific rotations and the circular dichroism spectra were
measured in the eluates, and the concentrations of which were
determined based on a comparison of the UV spectra with
those of authentic racemic samples. Chiroptical properties of
the optically active seleninic acids are summarized in Table 1,
and the chemical structures were confirmed by the Mass spectra
2-Methoxycarbonylbenzeneseleninic acid (4)21,22
1
Mp 147–148 ЊC; H NMR (500 MHz, CDCl3) δ 3.91 (s, 3H),
4.74 (s, 1H), 7.65 (d, 1H, J = 8.0 Hz), 7.81 (dd, 1H, J = 8.0, 8.0
Hz), 8.07 (dd, 1H, J = 8.0, 8.0 Hz), 8.21 (d, 1H, J = 8.0 Hz); 13
C
NMR (125 MHz, CD3OD) δ 53.6, 126.4, 129.8, 132.0, 133.4,
134.7, 148.2, 168.3; 77Se NMR (95 MHz, CD3OD) δ 1220;
UV (propan-2-ol): λmax 280 (ε 2.30 × 103), 235 (ε 7.92 × 103), 206
(ε 2.98 × 104) nm; MS (EI) m/z 246 (80Se, Mϩ Ϫ 2), 230, 228,
215, 213, 156, 77.
2,4,6-Trimethylbenzeneseleninic acid (5)
1
and H NMR spectra after concentration, although racemiz-
1
Mp 130–132 ЊC; H NMR (500 MHz, CDCl3) δ 2.29 (s, 3H),
ation was occurring during the concentration.
2.70 (s, 6H), 6.88 (s, 2H), 7.10 (br, 1H); 13C NMR (125 MHz,
CDCl3) δ 19.3, 21.2, 130.9, 139.2, 139.4, 142.7; 77Se NMR (95
MHz, CDCl3) δ 1245; IR (KBr) νmax 3200–2600, 2600–2000,
833, 804, 677 cmϪ1; UV (hexane–propan-2-ol = 90 : 10): λmax 274
(ε 2.53 × 103), 241 (ε 9.23 × 103), 213 (ε 2.02 × 104) nm; MS (EI)
m/z 231 (80Se, Mϩ Ϫ 1), 229 (78Se, Mϩ Ϫ 1), 199, 197, 119, 91.
Anal. Calcd for C9H12O2Se: C, 46.76; H, 5.23. Found: C, 46.67;
H, 5.17%.
Kinetic study for racemization of optically active areneseleninic
acids
Kinetic studies on the racemization of optically active seleninic
acids were examined in solutions (10Ϫ3–10Ϫ6 mol LϪ1) at 24 ЊC.
The rates of racemization were calculated based on their
circular dichroism spectra and were plotted to the first-order
rate equation.
2,4,6-Triethylbenzeneseleninic acid (6)
1
Mp 111–112 ЊC; H NMR (500 MHz, CDCl3) δ 1.22 (t, 3H,
Acknowledgements
J = 7.6 Hz), 1.32 (t, 6H, J = 7.6 Hz), 2.62 (q, 2H, J = 7.6 Hz),
3.15 (q, 4H, J = 7.6 Hz), 6.97 (s, 2H), 9.18 (br, 1H); 13C NMR
(125 MHz, CDCl3) δ 15.2, 17.0, 25.8, 28.7, 128.1, 139.1, 146.1,
149.0; 77Se NMR (95 MHz, CDCl3) δ 1276; IR (KBr) νmax 3100–
2600, 2600–2200, 871, 826, 796, 682 cmϪ1; UV (hexane–propan-
2-ol = 98 : 2): λmax 274 (ε 3.17 × 103), 238 (ε 6.59 × 103), 211
(ε 1.74 × 104) nm; MS (EI) m/z 273 (80Se, Mϩ Ϫ 1), 271 (78Se,
Mϩ Ϫ 1), 195, 161, 119, 91. Anal. Calcd for C12H18O2Se: C,
52.75; H, 6.64. Found: C, 52.81; H, 6.48%.
This work was financially supported in part by a Grant-in-Aid
for Scientific Research from the Ministry of Education, Science,
Sports, and Culture, Japan.
References
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2,4,6-Triisopropylbenzeneseleninic acid (7)
1
Mp 114–116 ЊC; H NMR (500 MHz, CDCl3) δ 1.24 (d, 6H,
J = 7.0 Hz), 1.33 (d, 12H, J = 6.7 Hz), 2.89 (septet, 1H,
J = 7.0 Hz), 4.07 (septet, 2H, J = 6.7 Hz), 6.56 (br, 1H), 7.11 (s,
2H); 13C NMR (125 MHz, CDCl3) δ 23.7, 24.7, 29.3, 34.5,
123.1, 139.3, 150.6, 153.4; 77Se NMR (95 MHz, CDCl3) δ 1200;
IR (KBr) νmax 3300–2500, 833, 816 cmϪ1; UV (hexane–propan-
2-ol = 99 : 1): λmax 275 (ε 3.18 × 103), 238 (ε 1.09 × 104), 211
(ε 2.66 × 104) nm; MS (EI) m/z 315 (80Se, Mϩ Ϫ 1), 313 (78Se,
Mϩ Ϫ 1), 284, 203, 117, 91. Anal. Calcd for C15H24O2Se: C,
57.14; H, 7.67. Found: C, 57.02; H, 7.54%.
2,4,6-Tri-tert-butylbenzeneseleninic acid (8)16
1
Mp 173 ЊC (decomp.); H NMR (500 MHz, CDCl3) δ 1.32 (s,
9H), 1.60 (br, 1H), 1.62 (br, 18H), 7.50 (s, 2H); 13C NMR (125
MHz, CDCl3) δ 31.1, 34.1, 35.2, 38.9, 124.5, 144.6, 153.0, 153.7;
77Se NMR (95 MHz, CDCl3) δ 1211; MS (EI) m/z 357 (80Se,
Mϩ Ϫ 1), 355 (78Se, Mϩ Ϫ 1), 342, 340, 244, 229, 81.
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2,4-Di-tert-butyl-6-methoxybenzeneseleninic acid (9)
1
Mp 101–103 ЊC; H NMR (500 MHz, CDCl3) δ 1.32 (s, 9H),
2154
J. Chem. Soc., Perkin Trans. 1, 2002, 2151–2155