H. Yu et al. / Tetrahedron 70 (2014) 8380e8384
8383
(Chiralcel AD-H), Hexei-PrOH 97:3, UV 210 nm, 0.9 mL minꢁ1, syn:
tR¼22.98 min (major) and tR¼30.85 min (minor).
CDCl3):
d
9.77 (d, J¼1.8 Hz,1H), 8.23e8.05 (m,1H), 7.90 (d, J¼8.0 Hz,
1H), 7.81 (d, J¼8.2 Hz, 1H), 7.63e7.34 (m, 4H), 5.00e4.83 (m, 3H),
3.10e2.93 (m, 1H), 0.99 (d, J¼7.3 Hz, 3H). HPLC conditions: The
enantiomeric excess was determined by HPLC (Chiralcel AS-H),
4.2.6. (2R,3S)-3-(4-Chlorophenyl)-2-methyl-4-nitrobutanal
(4ac).12h From aldehyde 2a and nitroolefin 3c at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
Hexane/i-PrOH¼90: 10, UV 210 nm, 0.8 mL minꢁ1
, syn:
tR¼37.14 min (major) and tR¼39.40 min (minor).
CDCl3):
d
9.70 (d, J¼1.5 Hz, 1H), 7.36e7.29 (m, 2H), 7.15e7.08 (m,
2H), 4.82e4.72 (m, 1H), 4.65e4.59 (m, 1H), 3.82e3.75 (m, 1H),
2.80e2.70 (m, 1H), 1.00 (d, J¼7.2 Hz, 3H). HPLC conditions: The
enantiomeric excess was determined by HPLC (Chiralcel AD-H),
Hexei-PrOH 97: 3, UV 210 nm, 0.9 ml minꢁ1, syn: tR¼24.16 min
(major) and tR¼33.93 min (minor).
4.2.13. (2R,3S)-2-Methyl-3-(naphthalen-2-yl)-4-nitrobutanal
(4aj).16d From aldehyde 2a and nitroolefin 3j at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
CDCl3):
d
9.75 (d, J¼1.6 Hz, 1H), 7.86e7.78 (m, 3H), 7.68e7.61 (m,
1H), 7.53e7.45 (m, 2H), 7.35e7.24 (m, 1H), 4.91e4.84 (m, 1H),
4.82e4.73 (m, 1H), 4.04e3.92 (m, 1H), 2.93e2.82 (m, 1H), 1.02 (d,
J¼7.3 Hz, 3H). HPLC conditions: The enantiomeric excess was de-
termined by HPLC (Chiralcel AS-H), Hexane/i-PrOH¼90: 10, UV
210 nm, 0.8 mL minꢁ1, syn: tR¼34.53 min (major) and tR¼41.53 min
(minor).
4.2.7. (2R,3S)-2-Methyl-4-nitro-3-(4-(trifluoromethyl)phenyl)buta-
nal (4ad).16c From aldehyde 2a and nitroolefin 3d at 0 ꢀC according
to the general procedure to give pale yellow oil. 1H NMR (400 MHz,
CDCl3):
d
9.71 (d, J¼1.4 Hz, 1H), 7.62 (d, J¼8.2 Hz, 2H), 7.31 (d,
J¼8.1 Hz, 2H), 4.86e4.80 (m, 1H), 4.74e4.66 (m, 1H), 3.95e3.85 (m,
1H), 2.90e2.75 (m, 1H), 1.00 (d, J¼7.4 Hz, 3H). HPLC conditions: The
enantiomeric excess was determined by HPLC (Chiralcel AD-H),
Hexei-PrOH 90: 10, UV 210 nm, 0.8 ml minꢁ1, syn: tR¼11.83 min
(major) and tR¼15.00 min (minor).
4.2.14. (2R,3S)-2-Methyl-4-nitro-3-(pyridin-3-yl)butanal
(4ak)).12j From aldehyde 2a and nitroolefin 3k at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
CDCl3):
d
9.70 (d, J¼1.4 Hz. 1H), 8.54e8.45 (m, 2H), 7.52e7.50 (m,
1H), 7.31e7.22 (m, 1H), 4.82e4.79 (m, 1H), 4.71e4.65 (m, 1H),
3.89e3.80 (m, 1H), 2.90e2.77 (m, 1H), 1.01 (d, J¼7.4 Hz, 3H). HPLC
conditions: The enantiomeric excess was determined by HPLC
4.2.8. (2R,3S)-2-Methyl-4-nitro-3-p-tolylbutanal (4ae).16b From al-
dehyde 2a and nitroolefin 3e at 0 ꢀC according to the general
procedure to give pale yellow oil. 1H NMR (400 MHz, CDCl3):
d
9.71
(Chiralcel OZ-H), Hexane/i-PrOH¼75: 25, UV 210 nm, 0.6 mL minꢁ1
,
(d, J¼2.0 Hz, 1H), 7.22e7.08 (m, 4H), 4.82e4.61 (m, 2H), 4.21e4.03
(m, 1H), 2.81e2.71 (m, 1H), 2.36 (s, 3H), 0.95 (d, J¼7.3 Hz, 3H). HPLC
conditions: The enantiomeric excess was determined by HPLC
syn: tR¼49.58 min (major) and tR¼61.62 min (minor).
4.2.15. (2R,3R)-3-(Furan-2-yl)-2-methyl-4-nitrobutanal (4al).12h
-
(Chiralcel AS-H), Hexane/i-PrOH¼95: 5, UV 210 nm, 0.9 mL minꢁ1
,
From aldehyde 2a and nitroolefin 3m at 0 ꢀC according to the
syn: tR¼23.11 min (major) and tR¼24.89 min (minor).
general procedure to give pale yellow oil. 1H NMR (400 MHz,
CDCl3):
d
9.71 (d, J¼1.0 Hz, 1H), 7.43e7.30 (m, 1H), 6.31e6.28 (m,
4.2.9. (2R,3S)-3-(4-Methoxyphenyl)-2-methyl-4-nitrobutanal
(4af).12h From aldehyde 2a and nitroolefin 3f at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
1H), 6.20e6.16 (m, 1H), 4.77e4.66 (m, 2H), 4.12e4.03 (m, 1H),
2.86e2.75 (m, 1H), 1.06 (d, J¼7.3 Hz, 3H). HPLC conditions: The
enantiomeric excess was determined by HPLC (Chiralcel AS-H),
CDCl3):
d
9.68 (d, J¼1.7 Hz,1H), 7.15e6.97 (m, 2H), 6.9e6.77 (m, 2H),
Hexane/i-PrOH¼90: 10, UV 210 nm, 0.8 mL minꢁ1
, syn:
4.82e4.71 (m, 1H), 4.67e4.59 (m, 1H), 3.78 (s, 3H), 3.75e3.71 (m,
1H), 2.81e2.63 (m, 1H), 0.98 (d, J¼7.3 Hz, 3H). HPLC conditions: The
enantiomeric excess was determined by HPLC (Chiralcel AS-H),
tR¼24.73 min (major) and tR¼22.85 min (minor).
4.2.16. (2R,3R)-2-Methyl-4-nitro-3-(thiophen-2-yl)butanal
(4am).12h From aldehyde 2a and nitroolefin 3m at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
Hexane/i-PrOH¼85: 15, UV 210 nm, 0.8 mL minꢁ1
, syn:
tR¼45.56 min (major) and tR¼35.23 min (minor).
CDCl3):
d
9.68 (d, J¼1.2 Hz, 1H), 7.25e7.21 (m, 1H), 6.97e6.87 (m,
4.2.10. (2R,3S)-3-(2-Methoxyphenyl)-2-methyl-4-nitrobutanal
(4ag).12h From aldehyde 2a and nitroolefin 3g at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
2H), 4.83e4.64 (m, 2H), 4.27e4.12 (m, 1H), 2.90e2.68 (m, 1H), 1.12
(d, J¼7.3 Hz, 3H). HPLC conditions: The enantiomeric excess was
determined by HPLC (Chiralcel OZ-H), Hexane/i-PrOH¼98: 2, UV
CDCl3)
d
9.71 (d, J¼1.8 Hz, 1H), 7.31e7.23 (m, 1H), 7.07 (dd, J¼7.5,
230 nm, 0.95 mL minꢁ1
,
syn: tR¼84.94 min (major) and
1.7 Hz, 1H), 6.96e6.83 (m, 2H), 4.90e4.81 (m, 1H), 4.77e4.70 (m,
1H), 4.10e3.96 (m, 1H), 3.83 (s, 3H), 3.09e2.91 (m, 1H), 0.93 (d,
J¼7.3 Hz, 3H). HPLC conditions: The enantiomeric excess was de-
termined by HPLC (Chiralcel AS-H), Hexane/i-PrOH¼98: 2, UV
tR¼57.27 min (minor).
Acknowledgements
210 nm, 0.95 mL minꢁ1
,
syn: tR¼45.50 min (major) and
Financial support by the NSFC (21402065) and the start-up fund
of Shanghai Institute of Technology is gratefully acknowledged.
tR¼43.61 min (minor).
4.2.11. (2R,3S)-3-(3-Methoxyphenyl)-2-methyl-4-nitrobutanal
(4ah).12j From aldehyde 2a and nitroolefin 4h at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,
Supplementary data
Supplementary data related to this article can be found at http://
CDCl3):
d
9.70 (d, J¼1.6 Hz, 1H), 7.26e7.21 (m, 1H), 6.82e6.67 (m,
3H), 4.79e4.73 (m, 1H), 4.68e4.62 (m, 1H), 3.77 (s, 3H), 3.83e3.72
(m, 1H), 2.82e2.69 (m, 1H), 1.00 (d, J¼7.3 Hz, 3H). HPLC conditions:
The enantiomeric excess was determined by HPLC (Chiralcel OZ-H),
References and notes
Hexane/i-PrOH¼90: 10, UV 210 nm, 0.8 mL minꢁ1
, syn:
tR¼40.97 min (major) and tR¼35.48 min (minor).
4.2.12. (2R,3S)-2-Methyl-3-(naphthalen-1-yl)-4-nitrobutanal
(4ai).12h From aldehyde 2a and nitroolefin 3i at 0 ꢀC according to
the general procedure to give pale yellow oil. 1H NMR (400 MHz,