drich, Acros, or Alfa Aesar and were used without further purifica-
tion. Water was distilled twice before use by conventional
(m, 1H), 3.61 (q, J=6.4 Hz, 1H), 3.82 (td, 1H), 3.98 (q, 1H), 5.76 (d,
1H), 7.23–7.48 (m, 5H) ppm. 13CNMR (100 MHz, CDCl3, TMS): d=
7.3, 14.1, 20.0, 22.7, 22.9–31.9, 49.5, 49.7, 64.2, 67.8, 68.4, 72.8,
125.9, 127.6, 128.5, 141.1, 182.5 ppm. Elemental Analysis: Calcd (%)
for C26H47NO4 (437.22): C 71.35, H 10.82, N 3.20; Found: C 70.43, H
9.73, N 3.47.
methods. NMR analyses were performed by using
a Bruker
400 MHz instrument. Chemical shifts are given in part per million
(ppm), measured from SiMe4 at d=0 ppm using the residual sol-
vent signal as secondary reference (d=2.51 ppm in 1HNMR for
[D6]DMSO and d=45.29 ppm for 13CNMR); coupling constants (J)
are given in hertz (Hz). In the description of spectra, the letters m
and t refer to multiplet and triplet, respectively.
Hydrogenation under hydrogen pressure: The stainless steel auto-
clave was charged with 10 mL of the NMeEph12X-stabilized Rh0
aqueous colloidal suspension and a magnetic stirrer. The ethylpyru-
vate (3.8ꢁ10À5 mol, 100 equiv) was added into the autoclave and
dihydrogen was admitted to the system at the desired pressure.
The conversion and the enantiomeric excess were determined by
gas chromatography. All analyses were performed using Carlo Erba
GC 6000 with FID detector equipped with a Chiralsil-Dex CB
column (30 m, 0.25 mm i.d.) Parameters were as follows: tempera-
ture 908C; injector temperature 2208C; detector temperature
2508C.
Transmission electron microscopy: A drop of the colloidal aqueous
suspensions was deposited onto a carbon-coated copper grid and
dried under air. Rhodium nanoparticles were observed by using a
transmission electron microscopy instrument (JEOL, JEM 100CX II
UHR) at an accelerating voltage of 100 kV.
Interface interactions: The surface tension of aqueous colloidal sol-
utions was measured with a drop tensiometer. A syringe with a
U-shaped needle was lowered into a sample cell containing an
aqueous solution of rhodium nanoparticles protected by the sur-
factant. An air bubble was produced from the syringe. The dynam-
ic surface tension was measured by filming the rising bubble and
analysing the contour of the bubble with a Tracker instrument
from IT Concept. The surface tension was determined at room
temperature for several surfactant concentrations.
Acknowledgements
We thank the Agence National de la Recherche (ANR) for the fi-
nancial support of the MesAsColl (ANR-08-CP2D).
Dynamic Light Scattering: The hydrodynamic size Dh and zeta po-
tential z of nanoparticle aggregates were measured by the dynam-
ic light scattering (DLS) technique, using a DelsaNano C (Beckmann
counter). The aqueous suspensions of rhodium nanoparticles were
analyzed at 258C and measurements were started 10 min after the
cell was placed in the DLS apparatus, to allow the temperature to
reach equilibrium.
Synthesis of (1R,2S)-(À)-N-MeEph12Br 2: N-methylephedrine (1 g,
5.6 mmol) and bromododecane (1.1 equiv, 6 mmol) were refluxed
in absolute ethanol for 48 h. After removal of the solvent under
pressure, the crude solid was washed with ethylacetate to afford a
white solid (75%). m.p.=968C; [a]D =À12.3 (c=10.4, CHCl3);
1HNMR (400 MHz, CDCl3, TMS): d=0.87 (t, J=6.8 Hz, 3H), 1.16 (d,
J=6.4 Hz, 3H), 1.24–1.32 (m, 16H), 1.62–1.77 (m, 2H), 2.87 (s, 1H),
3.29 (s, 3H), 3.45 (s, 3H), 3.49 (m, 1H), 3.61 (q, J=6.4 Hz, 1H), 3.82
(td, 1H), 5.76 (d, 1H), 7.23–7.48 (m, 5H) ppm. 13CNMR (100 MHz,
CDCl3, TMS): d=7.3, 14.1, 22.7, 22.9–31.9, 49.5, 49.7, 64.2, 67.8,
72.8, 125.9, 127.6, 128.5, 141.1 ppm. Elemental Analysis: Calcd (%)
for C23H42BrNO (427.9): C 64.47, H 9.88, N 3.27; Found: C 64.43, H
9.73, N 3.47.
Keywords: asymmetric hydrogenation
nanoparticles · N-methylephedrium · water
·
ethylpyruvate
·
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sodium salt (1 equiv 0.93 mmol) were refluxed in methanol for
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was removed under pressure. The crude solid was washed with
ethylacetate to afford a white solid. (1R, 2S)-(À)-N-MeEph12HCO3:
m.p.=96–1008C; [a]D =À11 (c=10, CHCl3); 1HNMR (400 MHz,
CDCl3, TMS): d=0.87 (t, J=6.8 Hz, 3H), 1.16 (d, J=6.4 Hz, 3H),
1.24–1.32 (m, 16H), 1.62–1.77 (m, 2H), 2.87 (s, 1H), 3.29 (s, 3H),
3.45 (s, 3H), 3.49 (m, 1H), 3.61 (q, J=6.4 Hz, 1H), 3.82 (td, 1H), 5.76
(d, 1H), 7.23–7.48 (m, 5H) ppm. 13CNMR (100 MHz, CDCl3, TMS):
d=7.3, 14.1, 22.7, 22.9–31.9, 49.5, 49.7, 64.2, 67.8, 72.8, 125.9,
127.6, 128.5, 141.1 ppm. Elemental Analysis: Calcd (%) for
C24H43NO4 (409.2): C 70.38, H 10.58, N 3.42; Found: C 69.26, H 9.92,
N 3.34. (1R, 2S)-(À)-N-MeEph12(S)-(À)-lactate: m.p.=968C; [a]D =
À10.3 (c=10, CHCl3); 1HNMR (400 MHz, CDCl3, TMS): d=0.87 (t,
J=6.8 Hz, 3H), 1.16 (d, J=6.4 Hz, 3H), 1.24–1.32 (m, 19H), 1.62–
1.77 (m, 2H), 2.1 (s, 1H), 2.87 (s, 1H), 3.29 (s, 3H), 3.45 (s, 3H), 3.49
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Received: July 7, 2010
Revised: July 23, 2010
Published online on September 24, 2010
ChemSusChem 2010, 3, 1276 – 1279
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1279