1904
Y. Tang et al. / Tetrahedron: Asymmetry 21 (2010) 1900–1905
4.1.5. (1R,2R)-N-(3,5-Ditrifluoromethylbenzylsulfonyl)-1,2-
4.2.4. (S)-1,2-Dimethoxy-4-(1-nitropropan-2-yl)benzene
94% Yield. HPLC conditions: OD-H, 254 nm, 1.0 mL/min, hexane/
i-PrOH = 80:20. Minor enantiomer: tR = 10.23 min; major enantio-
bis(4-methoxyphenyl)-1,2-ethylenediamine
White solid, 76% yield. Mp: 155.8–157.6 °C. ½a D20
¼ þ129:2 (c
ꢂ
0.5, MeOH). 1H NMR (300 MHz, CDCl3): d 3.71 (s, 3H), 3.72 (s,
3H), 4.04 (d, J = 5.7 Hz, 1H), 4.43 (d, J = 5.8 Hz, 1H), 6.61 (d,
J = 8.7 Hz, 2H), 6.65 (d, J = 8.7 Hz, 2H), 6.95 (d, J = 8.6 Hz, 2H),
7.01 (d, J = 8.6 Hz, 2H), 7.81 (s, 1H), 7.87 (s, 2H). 13C NMR
mer: tR = 13.33 min, ee = 86%. ½a D20
ꢂ
¼ ꢀ52:0 (c 0.60, CHCl3). 1H
NMR (300 MHz, CDCl3): d 1.36 (d, J = 7.0 Hz, 3H), 3.58 (app. sextet,
J = 7.3 Hz, 1H), 3.86 (s, 3H), 3.88 (s, 3H), 4.42–4.55 (m, 2H), 6.72 (d,
J = 1.9 Hz, 1H), 6.77 (dd, J = 2.0 Hz, 8.2 Hz, 1H), 6.83 (d, J = 8.2 Hz,
1H). 13C NMR (CDCl3, 75 MHz): d 18.8, 38.3, 55.90, 55.93, 82.1,
110.3, 111.6, 118.8, 133.4, 148.4, 149.2. HRMS (ESI) calcd for
(75 MHz, CDCl3):
d 55.0, 59.6, 63.1, 113.7, 113.8, 122.4 (q,
J = 271.6 Hz), 125.2 (app. septet, J = 3.5 Hz), 127.2, 127.25, 127.3,
128.3, 129.8, 132.1 (q, J = 34.1 Hz), 133.2, 143.5, 158.9, 159.1.
HRMS (ESI) calcd for C24H23F6N2O4S [M+H] 549.1277, found
549.1269.
C11H16NO4 [M+H] 226.1079, found 226.1082.
4.2.5. (S)-1-Methyl-4-(1-nitropropan-2-yl)benzene
92% Yield. HPLC conditions: OD-H, 215 nm, 1.0 mL/min, hexane/
i-PrOH = 90:10. Minor enantiomer: tR = 7.25 min; major enantio-
4.1.6. (1R,2R)-N-Trifluoromethanesulfonyl-1,2-bis(3-nitro-
phenyl)-1,2-ethylenediamine
mer: tR = 10.23 min, ee = 79%. ½a D20
ꢂ
¼ ꢀ48:3 (c 0.60, CHCl3). 1H
White solid, 28% yield. Mp: 184.0–186.5 °C. ½a D20
ꢂ
¼ þ60:7 (c 0.5,
NMR (300 MHz, CDCl3): d 1.37 (d, J = 7.0 Hz, 3H), 2.33 (s, 3H),
3.60 (app. sextet, J = 7.2 Hz, 1H), 4.43–4.56 (m, 2H), 7.11 (d,
J = 8.4 Hz, 2H), 7.15 (d, J = 8.3 Hz, 2H). All other spectroscopic data
are in agreement with the literature.5
MeOH). 1H NMR (300 MHz, CD3OD): d 4.51 (d, J = 8.1 Hz, 1H), 4.82
(d, J = 8.1 Hz, 1H), 7.45 (t, J = 7.9 Hz, 1H), 7.55–7.60 (m, 2H), 7.70 (d,
J = 7.8 Hz, 1H), 8.05–8.08 (m, 1H), 8.17–8.21 (m, 2H), 8.29 (d,
J = 1.7 Hz, 1H). 13C NMR (75 MHz, CD3OD) d 62.4, 65.1, 122.3 (q,
J = 322.8 Hz), 123.5, 123.9, 124.6, 130.5, 131.1, 135.0, 135.4,
139.8, 144.3, 149.6, 149.7. HRMS (ESI) calcd for C15H14F3N4O6S
[M+H] 435.0581, found 435.0586.
4.2.6. (S)-1-Fluoro-4-(1-nitropropan-2-yl)benzene
99% Yield. HPLC conditions: OD-H, 254 nm, 1.0 mL/min, hexane/
i-PrOH = 95:5. Minor enantiomer: tR = 18.93 min; major enantio-
mer: tR = 20.17 min, ee = 82%. ½a D20
ꢂ
¼ ꢀ46:3 (c 0.60, CHCl3). 1H
4.2. Asymmetric transfer hydrogenation of b,b-disubstituted
nitroalkene
NMR (300 MHz, CDCl3): d 1.37 (d, J = 7.0 Hz, 3H), 3.63 (app. sextet,
J = 7.3 Hz, 1H), 4.43–4.55 (m, 2H), 6.99–7.07 (m, 2H), 7.17–7.22 (m,
2H). All other spectroscopic data are in agreement with the
literature.4c,5
General procedure: A mixture of the ligand (0.0044 mmol) and
[RhCl2Cp*]2 (0.002 mmol) in a glass tube was degassed three times
followed by introducing 1 mL of degassed water. After stirring at
40 °C for 1 h, HCO2Na (790 mg, 11.6 mmol or 760 mg, 11.2 mmol),
4.2.7. (S)-1-Chloro-3-(1-nitropropan-2-yl)benzene
95% Yield. HPLC conditions: OD-H, 215 nm, 1.0 mL/min, hexane/
i-PrOH = 90:10. Minor enantiomer: tR = 9.06 min; major enantio-
HCO2H (15.1 lL, 0.4 mmol or 30.2 lL, 0.8 mmol) and the substrate
mer: tR = 12.30 min, ee = 86%. ½a D20
ꢂ
¼ ꢀ40:6 (c 0.55, CHCl3). 1H
(0.4 mmol) were added. The mixture was degassed three times and
then stirred at 28 °C under argon atmosphere for the correspond-
ing time. The aqueous layer was extracted with ether (5 mL ꢁ 3).
The combined organic layers were dried over Na2SO4, filtered
and concentrated under reduced pressure to afford the crude prod-
uct, which was purified by flash chromatography (PE/EtOAc) on sil-
ica gel to provide the pure reduction products.
NMR (300 MHz, CDCl3): d 1.38 (d, J = 7.0 Hz, 3H), 3.62 (app. sextet,
J = 7.3 Hz, 1H), 4.44–4.57 (m, 2H), 7.10–7.13 (m, 1H), 7.22–7.28 (m,
3H). All other spectroscopic data are in agreement with the
literature.5
4.2.8. (S)-1-Chloro-4-(1-nitropropan-2-yl)benzene
96% Yield. HPLC conditions: OD-H, 215 nm, 1.0 mL/min, hexane/
i-PrOH = 90:10. Minor enantiomer: tR = 8.49 min; major enantio-
4.2.1. (S)-(1-Nitropropan-2-yl)benzene
99% Yield. GC conditions: CP CYCLODEX B 236M, 115–260 °C.
Major enantiomer: tR = 46.34 min, minor enantiomer: tR = 47.8
mer: tR = 10.83 min, ee = 83%. ½a D20
ꢂ
¼ ꢀ43:5 (c 0.55, CHCl3). 1H
NMR (300 MHz, CDCl3): d 1.38 (d, J = 7.0 Hz, 3H), 3.64 (app. sextet,
J = 7.3 Hz, 1H), 4.46–4.58 (m, 2H), 7.18–7.20 (m, 2H), 7.29–7.35 (m,
2H). All other spectroscopic data are in agreement with the
literature.4c,5
min; ee = 86%. ½a 2D0
ꢂ
¼ ꢀ36:8 (c 0.70, CHCl3). 1H NMR (300 MHz,
CDCl3): d 1.39 (d, J = 7.0 Hz, 3H), 3.64 (app. sextet, J = 7.2 Hz, 1H),
4.45–4.59 (m, 2H), 7.22–7.30 (m, 3H), 7.33–7.38 (m, 2H). All other
spectroscopic data are in agreement with the literature.4c,5
4.2.9. (S)-1-Bromo-4-(1-nitropropan-2-yl)benzene
4.2.2. (S)-1-Methoxy-3-(1-nitropropan-2-yl)benzene
94% Yield. HPLC conditions: OD-H, 215 nm, 1.0 mL/min, hexane/
i-PrOH = 90:10. Minor enantiomer: tR = 9.77 min; major enantio-
90% Yield. HPLC conditions: OD-H, 254 nm, 1.0 mL/min, hexane/
i-PrOH = 80:20. Minor enantiomer: tR = 9.66 min; major enantio-
mer: tR = 14.43 min, ee = 82%. ½a D20
ꢂ
¼ ꢀ36:0 (c 0.50, CHCl3). 1H
mer: tR = 15.48 min, ee = 90%. ½a D20
ꢂ
¼ ꢀ43:3 (c 0.60, CHCl3). 1H
NMR (300 MHz, CDCl3): d 1.36 (d, J = 7.0 Hz, 3H), 3.61 (app. sextet,
J = 7.3 Hz, 1H), 4.43–4.56 (m, 2H), 7.09–7.13 (m, 2H), 7.45–7.49 (m,
2H). All other spectroscopic data are in agreement with the
literature.4c
NMR (300 MHz, CDCl3): d 1.37 (d, J = 7.0 Hz, 3H), 3.61 (app. sextet,
J = 7.2 Hz, 1H), 3.80 (s, 3H), 4.43–4.58 (m, 2H), 6.76–6.83 (m, 3H),
7.26 (t, J = 8.0 Hz, 1H). All other spectroscopic data are in agree-
ment with the literature.4c
4.2.10. (S)-2-(1-Nitropropan-2-yl)naphthalene
4.2.3. (S)-1-Methoxy-4-(1-nitropropan-2-yl)benzene
90% Yield. HPLC conditions: OD-H, 215 nm, 1.0 mL/min, hexane/
i-PrOH = 90:10. Minor enantiomer: tR = 18.36 min; major enantio-
96% Yield. HPLC conditions: OD-H, 254 nm, 1.0 mL/min, hexane/
i-PrOH = 80:20. Minor enantiomer: tR = 6.94 min; major enantio-
mer: tR = 60.19 min, ee = 78%. ½a D20
ꢂ
¼ ꢀ47:9 (c 0.50, CHCl3). 1H
mer: tR = 9.94 min, ee = 81%. ½a D20
ꢂ
¼ ꢀ44:1 (c 0.55, CHCl3). 1H
NMR (300 MHz, CDCl3): d 1.50 (d, J = 7.0 Hz, 3H), 3.84 (app. sextet,
J = 7.3 Hz, 1H), 4.57–4.72 (m, 2H), 7.38 (dd, J = 1.8 Hz, 8.5 Hz, 1H),
7.49–7.54 (m, 2H), 7.70 (s, 1H), 7.82–7.88 (m, 3H). All other spec-
troscopic data are in agreement with the literature.5
NMR (300 MHz, CDCl3): d 1.38 (d, J = 7.0 Hz, 3H), 3.61 (app. sextet,
J = 7.3 Hz, 1H), 3.82 (s, 3H), 4.44–4.57 (m, 2H), 6.88–7.92 (m, 2H),
7.16–7.19 (m, 2H). All other spectroscopic data are in agreement
with the literature.4c