Chiral, Ammonium-Capped Rhodium(0) Nanocatalysts
ring was 1 mm. Equilibrium surface tension was measured three
times at 330 K for each concentration using a Harkins and Jordan
correction method.
to afford (1R,2S)-N-hexadecyl-N-methylprolinolinium l-tartrate with
a purity of 98%. A solution of CaBr2·2H2O (0.44 g, 1.86 mmol) in
water (5 mL) was added dropwise to an aqueous solution (6 mL) of
this salt (1.54 g, 1.86 mmol) heated at 608C. After stirring at 608C
for 20 min and cooling to room temperature, the white precipitate
of calcium tartrate was filtered. After centrifugation, compound 6
was obtained (21%). [a]2D0 =+3 (c=10 in CH3OH); 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=0.8 (t, J=7 Hz, 3H), 1.2 (m, 22H),
1.5 (m, 4H), 1.9 (m, 2H), 2.1 (m, 3H), 2.32 (m, 1H), 3 (s, 3H), 3.5–3.7
(m, 3H), 3.82 (m, 1H), 4–4.4 ppm (m, 4H); 13C NMR (100 MHz,
CDCl3, 258C, TMS): d=14.5, 21.0, 23.8, 24.7, 25.3, 27.8, 30.3–33.1,
50.7, 57.8, 60.2, 65.8, 66.9, 78.8 ppm; IR (KBr): n˜ =3140 cmÀ1 (OÀH);
elemental analysis calcd (%) for C22H46BrNO (375.5): C 62.84,
H 11.03, N 3.33; found: C 61.99, H 11.68, N 3.01
Dynamic light scattering: The hydrodynamic diameters, Dh, and
zeta potential, z, values of the nanoparticle aggregates were mea-
sured by performing the DLS technique using a DelsaNano C
(Beckmann counter) instrument. Aqueous suspensions of rhodi-
um(0) nanoparticles were analyzed at 258C, and measurements
began 10 min after the cell was placed in the DLS apparatus to
allow the temperature to equilibrate.
Syntheses of the bromides
Synthesis of N-dodecyl-N-methylephredinium bromide (2): N-Meth-
ylephedrine (1 g, 5.6 mmol) and bromododecane (1.1 equiv,
6 mmol) were heated at reflux in absolute ethanol for 48 h. After
removal of the solvent under pressure, the crude solid was washed
Synthesis of (1S,2S,4S,5R)-(+)-N-hexadecyl-5-vinyl-2-quinuclidinium-
methanol bromide (8): (2S, 4S, 5R)-(+)-5-Vinyl-2-quinuclidinemetha-
nol or quincorine (502 mg, 3 mmol) and bromohexadecane
(1.2 equiv, 3.6 mmol) were heated at reflux in acetone (5 mL) for
2 d. After cooling to room temperature and filtration, the crude
solid was washed with diethyl ether to afford 8 as a white solid
(69%). M.p. 1158C; [a]D20 =+13.7 (c=10.4 in MeOH); 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=0.9 (t, J=7 Hz, 3H), 1.36 (m, 26H),
1.73 (m, 3H), 2.0–2.3 (m, 4H), 2.89 (m, 1H), 3.17–3.38 (m, 2H),
3.40–3.79 (m, 5H), 3.88 (m, 2H), 5.25 (m, 2H), 5.99 ppm (m, 1H);
13C NMR (100 MHz, CDCl3, 258C, TMS): d=14.5, 23.2–23.8, 24.8,
26.2, 27.7, 28.0, 28.1–33.1, 39.4, 54.0, 61.99, 62.03, 63.6, 65.7, 117.9,
138.6 ppm; IR (KBr): n˜ =3237 cmÀ1 (OÀH); elemental analysis calcd
(%) for C26H40BrNO (472.15): C 66.08, H 10.66, N 2.96; found:
C 66.18, H 10.70, N 3.05.
with ethyl acetate to afford a white solid (75%). M.p. 968C; [a]D20
=
À16 (c=10 in MeOH); 1H NMR (400 MHz, CDCl3, 258C, 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 ppm (m, 5H); 13C NMR (100 MHz, CDCl3, 258C, 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; IR (KBr): n˜ =3147.14 cmÀ1 (OÀH); 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.
Synthesis of (2S)-N-hexadecyl-N-methyl-prolinolinium bromide (4):
(S)-N-Methylprolinol (970 mg, 8.4 mmol) and bromohexadecane
(1.3 equiv, 10.7 mmol) were heated at reflux in acetone (10 mL) for
3 d. After precipitation by cooling and filtration, the product was
washed with diethyl ether to yield a white solid (90%). M.p. 176–
1798C; [a]2D0 =À1.5 (c=10 in CH3OH); 1H NMR (400 MHz, CDCl3,
258C, TMS): d=0.9 (t, J=7 Hz, 3H), 1.3 (m, 22H), 1.41 (m, 4H), 1.82
(m, 2H), 2.1 (m, 3H), 2.32 (m, 1H), 3.03 (s, 3H), 3.19 (s, 3H), 3.32–
3.52 (m, 3H), 3.62 (m, 1H), 3.75–3.88 ppm (m, 4H); 13C NMR
(100 MHz, CDCl3, 258C, TMS): d=14.5, 20.8–21.0, 23.8, 24.2–24.7,
24.9–25.3, 27.8, 30.3–33.1, 43.4, 50.7, 57.8, 60.2, 64.4–65.8, 66.9,
77.0–78.8 ppm; IR (KBr): n˜ =3264 cmÀ1 (OÀH); elemental analysis
calcd (%) for C22H46BrNO (375.5): C 62.84, H 11.03, N 3.33; found:
C 62.90, H 10.77, N 3.33.
Synthesis of (1S,2R,4S,5R)-(+)-N-hexadecyl-5-vinyl-2-quinuclidini-
um-methanol bromide (10): (2R, 4S, 5R)-(+)-5-Vinyl-2-quinuclidine-
methanol or quincoridine (502 mg, 3 mmol) was alkylated with
bromohexadecane (1.2 equiv, 3.6 mmol) as described above for 8.
After precipitation, filtration, and washing with diethyl ether, com-
pound 10 was obtained as a white solid (81%). M.p. 1538C; [a]D20
=
1
+1.3 (c=4.7 in MeOH); H NMR (400 MHz, CDCl3, 258C, TMS): d=
0.91 (t, J=7 Hz, 3H), 1.35 (m, 26H), 1.80 (m, 2H), 1.92–2.20 (m,
5H), 2.83 (m, 1H), 3.22 (m, 1H), 3.31–3.63 (m, 6H), 3.77–4.06 (m,
3H), 5.23 (m, 2H), 5.94 ppm (m, 1H); 13C NMR (100 MHz, CDCl3,
258C, TMS): d=14.5, 23.6–23.8, 23.8, 25.3, 27.8, 28.2, 30.3–30.1,
39.4, 56.5, 57.9, 60.6, 62.1, 66.4, 117.8, 137.7 ppm; IR (KBr): n˜ =
3255 cmÀ1 (OÀH); elemental analysis calcd (%) for C26H40BrNO
(472.15): C 66.08, H 10.66, N 2.96; found: C 66.17, H 10.59, N 3.03.
Synthesis of (1S,2S)-(À)-N-hexadecyl-N-methylprolinolinium bro-
mide (5): The diastereomer was isolated with a purity of 96% by
means of recrystallization of the diastereomeric bromide mixture
1
from acetone 13 times (20%). [a]2D0 =À3 (c=10 in CH3OH); H NMR
General procedure for the metathesis reaction, preparation,
and characterization of the lactate salts
(400 MHz, CDCl3, 258C, TMS): d=0.8 (t, J=7 Hz, 3H), 1.2 (m, 22H),
1.5 (m, 4H), 1.9 (m, 2H), 2.1 (m, 3H), 2.32 (m, 1H), 3.3 (s, 3H), 3.5–
3.7 (m, 3H), 3.82 (m, 1H), 4–4.4 ppm (m, 4H); 13C NMR (100 MHz,
CDCl3, 258C, TMS): d=14.5, 21.0, 23.8, 24.7, 25.3, 27.8, 30.3–33.1,
50.7, 57.8, 60.2, 65.8, 66.9, 78.8 ppm; IR (KBr): n˜ =3264 cmÀ1 (OÀH);
elemental analysis calcd (%) for C22H46BrNO (375.5): C 62.84,
H 11.03, N 3.33; found: C 62.80, H 10.87, N 3.31.
The lactate salts were synthesized by ion-exchange reactions in
methanol from the previously obtained chiral ammonium surfac-
tants and (D) or (L)-sodium lactate in a molar ratio of 1:1 under
heating at reflux. After the reaction, the resulting mixture was fil-
tered through Celite and the solvent was removed to afford a
white solid that could be used without further purification.
Synthesis of (1R,2S)-(+)-N-hexadecyl-N-methylprolinolinium bro-
mide (6): Silver oxide (1.49 g, 6.46 mmol) and l-tartaric acid
(0.971 g, 6.47 mmol) dissolved in methanol (20 mL) was stirred at
room temperature until complete precipitation of white silver tar-
trate. After addition of the diasteromeric mixture of N-hexadecyl-N-
methyl-l-prolinolinium bromides (5.42 g, 12.9 mmol), the solution
was stirred for 24 h. After filtration and removal of the solvent,
N-hexadecyl-N-methyl-l-prolinolinium l-tartrate was obtained as a
yellow solid (97%). The solid was recrystallized 9 times in acetone
Compound 11: Yield=98%; m.p. 1068C; [a]2D0 =+7.7 (c=4.7 in
CH3OH); H NMR (400 MHz, CDCl3, 258C, TMS): d=0.80 (t, J=7 Hz,
1
3H), 1.19–1.28 (m, 29H), 1.58–1.74 (m, 2H), 1.90–2.17 (m, 5H),
2.71–2.79 (m, 1H), 3.05–3.12 (m, 1H), 3.21–3.52 (m, 6H), 3.58–3.97
(m, 3H), 5.18 (m, 2H), 5.87 ppm (m, 1H); 13C NMR (100 MHz, CDCl3,
258C, TMS): d=14.5, 21.7, 23.2–23.7, 24.8, 26.2, 27.6, 28.0, 30.2–
33.1, 39.4, 54.0, 60.0, 62.0, 63.6, 65.7, 69.6, 117.9, 137.6, 182.3 ppm;
IR (KBr): n˜ =1617 (C=O), 3447 cmÀ1 (OÀH).
ChemSusChem 2012, 5, 91 – 101
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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