Arkivoc 2018, vii, 0-0
Mondal, A. et al.
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was purified by column chromatography. A colourless semi-solid 5 was obtained. Yield= 259 mg (80%). [α]D
=
-30 (c 1.0, CHCl3); IR (film, cm-1): 3346, 2962, 2876, 1721, 1661, 1528; 1H NMR (400 MHz, CDCl3) δ 0.904 (6H, d,
J=6.4 Hz), 1.455 (9H, s), 1.713-1.976 (5H, m), 3.221-3.436 (4H, m), 3.799-3.930 (3H, m), 5.873 (1H, s); 13C NMR
(101 MHz, CDCl3) 19.17, 23.23, 23.99, 28.14, 28.57, 29.31, 44.81, 44.07, 44.09, 56.98, 71.07, 79.87, 156,
157.42; HRMS (m/z): calcd for C15H28N2O4 [M+Na]: 323.1947; found: 323.1952.
Procedure for preparation of compound 1. The BOC protected colourless semi-solid 5 (323 mg, 1 mmol) was
dissolved in a mixture of TFA (1 ml) and DCM (4 ml) and stirred for two hours at room temperature. Then the
mixture was basified with concentrated ammonia solution. The organic layer was separated and the aqueous
phase was extracted two times by dichloromethane. The combined organic layer was then dried over sodium
sulphate and evaporated under vacuum to give a yellowish semi-solid 1. Yield= 191 mg (95%). [α]D20= -20 (c
1
1.0, CHCl3); IR (film, cm-1): 3400, 2962, 2875, 2375, 1717, 1571; H NMR (400 MHz, CDCl3) δ 0.91 (6H, d, J=6.8
Hz), 1.44-1.91 (6H, m), 2.98-3.31 (4H, m), 3.81 (3H, m), 5.50 (1H, s); 13C NMR (101 MHz, CDCl3) 19.16, 22.81,
25.68, 28.13, 29.81, 44.77, 58.45, 71.19, 157.38; TOF MS ES+ (m/z): calcd for C10H20N2O2 [M+]: 201.1500;
found: 201.1300.
General Procedure for asymmetric Michael addition reaction. To a stirred solution of catalyst 1 in brine,
additive was added followed by ketone at room temperature. After 15 minutes of stirring, nitrostyrene was
added and the reaction mixture was stirred vigorously at room temperature for 3-6 days and monitored by
TLC. The Michael product was then purified by column chromatography using hexane/ethylacetate.
(S)-2-((R)-2-Nitro-1-phenylethyl)cyclohexanone (6). NMR data matched with the previously reported one.59
The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane : IPA (90:10), Flow rate =
0.5 ml/min; λ =254 nm; tR(minor) = 22.5 min, tR(major) = 27.7 min.
(S)-2-((R)-1-(3-Chlorophenyl)-2-nitroethyl)cyclohexanone (7). NMR data matched with the previously
reported one.60 The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane : IPA
(90:10), Flow rate = 0.5 ml/min; λ =254 nm; tR(minor) = 22.597 min, tR(major) = 24.454 min.
(S)-2-((R)-2-Nitro-1-(2-nitrophenyl)ethyl)cyclohexanone (8). NMR data matched with the previously reported
one.59 The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane : IPA (85:15), Flow
rate = 0.5 ml/min; λ =254 nm; tR(minor) = 16.863 min, tR(major) = 27.665 min.
(S)-2-((R)-2-Nitro-1-p-tolylethyl)cyclohexanone (9). NMR data matched with the previously reported one.61
The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane : IPA (96:4), Flow rate = 0.5
ml/min; λ =254 nm; tR(minor) = 30.049 min, tR(major) = 39.336 min.
(S)-2-((R)-1-(3-Fluorophenyl)-2-nitroethyl)cyclohexanone (10). NMR data matched with the previously
reported one.59 The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane : IPA
(90:10), Flow rate = 0.5 ml/min; λ =254 nm; tR(minor) = 22.884 min, tR(major) = 25.720 min.
(S)-2-((R)-1-(2-Fluorophenyl)-2-nitroethyl)cyclohexanone (11). NMR data matched with the previously
reported one.62 The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane : IPA
(90:10), Flow rate = 0.5 ml/min; λ =254 nm; tR(minor) = 20.263 min, tR(major) = 23.941 min.
(S)-2-((R)-1-(2-Chlorophenyl)-2-nitroethyl)cyclohexanone (12). NMR data matched with the previously
reported one.59 The ee value was determined by the AD-H chiral column.Mobile phase = n-Hexane : IPA (95:5),
Flow rate = 0.5 ml/min; λ =254 nm; tR(minor) = 30.121 min, tR(major) = 52.219 min.
(S)-2-((R)-2-Nitro-1-(4-(trifluoromethyl)phenyl)ethyl)cyclohexanone (13). NMR data matched with the
previously reported one.61 The ee value was determined by the AD-H chiral column. Mobile phase = n-Hexane
: IPA (90:10), Flow rate = 0.5 ml/min; λ =254 nm; tR(minor) = 22.326 min, tR(major) = 43.176 min.
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