JOURNAL OF CHEMICAL RESEARCH 2012 643
chromatography on silica gel to give the desired product 3 as a pale
yellow solid (2.19 g, 35% yield). M.p. 66–67 °C. 1H NMR (500 MHz,
CDCl3,TMS) δ 7.60 (s, 1H), 7.07 (s, 1H), 7.03 (s, 1H), 4.54 (d, J = 2.5
Hz, 1H), 1.96–1.88 (m, 2H), 1.79–1.70 (m, 2H), 1.50–1.38 (m, 2H),
1.35–1.29 (m, 1H), 1.24–1.17 (m, 1H), 1.08–0.99 (m, 1H), 0.88 (d,
into a 50 mL flask. The flask was covered with aluminum foil
and stirred at room temperature for 3 h. The resulting mixture was
filtered quickly, and the filtrate was transferred to a second 50-mL
round-bottom flask, which was also covered with aluminum foil.
After adding [{RhCl(COD)}2] (246.5 mg, 0.50 mmol) and CH2Cl2
(10.0 mL), the mixture was stirred for an additional 6 h at room tem-
perature and then was filtered through Celite. The solvent was removed
under reduced pressure and the residue was purified by a flash chro-
matography on silica gel (CH2Cl2) to give the Rh(I)-NHC complex 6
as a yellow solid (401.7 mg, 86%). The single crystal for X-ray
diffraction was obtained by recrystallisation from CH2Cl2 and ethyl
acetate (4:1). M.p. 174–176 °C (decomposed). MS (ESI) m/z 431
[M-Cl]+. IR (neat) ν 2924, 2870, 1454, 1440, 1389, 1262, 1228, 1194,
750, 737, 704 cm−1. Anal. Calcd for C22H36ClN2Rh: C, 56.59; H, 7.77,
N, 6.00. Found: C, 56.72; H, 7.93, N, 5.92%.
J = 6.5 Hz, 3H), 0.84 (d, J = 6.5 Hz, 3H), 0.78 (d, J = 6.5 Hz, 3H). 13
C
NMR (125 MHz, CDCl3) δ 137.9, 128.4, 120.2, 55.6, 46.5, 41.7, 34.3,
29.1, 26.7, 25.4, 22.3, 21.2, 20.3. HRMS (ESI): Calcd for C13H23N2
[M+H]+ requires 207.1857; found: 207.1858. IR (neat) ν 2954,
2926, 2875, 1489, 1452, 1261, 1222, 1110, 1079, 909, 806, 744, 734,
670 cm−1.
Synthesis of 4: CH3I (0.80 mL, 12.84 mmol) was added to a CH3CN
(20 mL) solution containing compound 3 (1.32 g, 6.40 mmol) at room
temperature. The solution was kept at 80 °C for 6 h. The solvent was
then removed under vacuum to give a yellow solid, which was washed
with Et2O (15 mL) to afford compound 4 as a pale-yellow solid (2.11g,
95%). M.p. 169–171 °C (decomposed). 1H NMR (500 MHz, CDCl3,
TMS) δ 10.31 (s, 1H), 7.40 (s, 2H), 4.98 (s, 1H), 4.23 (s, 3H), 2.07–
1.98 (m, 3H), 1.75 (br, 1H), 1.59–1.44 (m, 3H), 1.27–1.20 (m, 1H),
1.09–1.02 (m, 1H), 0.93 (d, J = 5.5 Hz, 3H), 0.91 (d, J = 5.5 Hz, 3H),
0.86 (d, J = 6.5 Hz, 3H). 13C NMR (125 MHz, CDCl3) δ 136.9, 123.2,
123.0, 60.1, 45.7, 40.5, 37.2, 33.6, 29.0, 26.0, 24.8, 22.0, 21.5, 20.5.
HRMS (ESI): Calcd for C14H25N2 [M-I]+ requires 221.2012; found:
221.2013. IR (neat) ν 3067, 2948, 2915, 2862, 1503, 1454, 1265,
1198, 1152, 1136, 867, 745, 735 cm−1.
Financial support from the National Natural Science Founda-
tion of China (No. 21002072) and the Opening Foundation of
Zhejiang Provincial Top Key Discipline (No. 1000612001) is
greatly appreciated.
Received 16 April 2012; accepted 22 August 2012
Paper 1201266 doi: 10.3184/174751912X13467827890747
Published online: 12 November 2012
Synthesis of 5: Compound 4 (348.1 mg, 1.0 mmol), Ag2O (118.2 mg,
0.51 mmol) and CH2Cl2 (5.0 mL) were added under an N2 atmosphere
into a 50 mL flask. Then the flask was covered with aluminum foil
and stirred at room temperature for 3 h. The resulting mixture was
filtered quickly, and the filtrate was transferred to a second 50 mL
round-bottom flask, which was also covered with aluminum foil. After
adding [PdCl2 (COD)] (143.9 mg, 0.50 mmol) and CH2Cl2 (10.0 mL),
the mixture was stirred for an additional 6 h at room temperature and
then was filtered through Celite. The solvent was removed under
reduced pressure and the residue was purified by flash chromatogra-
phy on silica gel (CH2Cl2) to give the Pd(II)-NHC complex 5 as a pale
yellow solid (243.0 mg, 78%). The single crystal for X-ray diffraction
was obtained by recrystallisation from acetone and ethyl acetate (5:1).
M.p. 248–250 °C (decomposed). (trans- or cis-isomer) 1H NMR
(500 MHz, CDCl3,TMS) δ 7.16 (d, J = 3.0 Hz, 2H), 6.79 (d, J =
1.5 Hz, 2H), 5.87 (d, J = 2.0 Hz, 2H), 4.18 (s, 6H), 2.52 (d, J =
14.0 Hz, 2H), 1.94–1.90 (m, 4H), 1.68–1.63 (m, 4H), 1.55–1.50 (m,
4H), 1.44–1.36 (m, 2H), 1.17 (d, J = 5.5 Hz, 6H), 1.15–1.04 (m, 2H),
0.87 (d, J = 6.0 Hz, 6H), 0.79 (d, J = 6.5 Hz, 6H). (cis- or trans-
isomer) 1H NMR (500 MHz, CDCl3,TMS) δ 7.16 (d, J = 2.0 Hz, 2H),
6.78 (d, J = 2.0 Hz, 2H), 5.83 (d, J = 2.5 Hz, 2H), 4.14 (s, 6H), 2.68
(d, J = 16.5 Hz, 2H), 1.94–1.90 (m, 4H), 1.68–1.63 (m, 4H), 1.55–
1.50 (m, 4H), 1.44–1.36 (m, 2H), 1.16 (d, J = 6.5 Hz, 6H), 1.15–1.04
(m, 2H), 0.87 (d, J = 6.0 Hz, 6H), 0.81 (d, J = 5.5 Hz, 6H). (trans- or
cis-isomer) 13C NMR (125 MHz, CDCl3) δ 170.8, 121.2, 120.8, 58.2,
46.7, 41.7, 37.7, 34.5, 29.0, 26.5, 25.2, 22.7, 22.4, 20.3. (cis- or trans-
isomer) 13C NMR (125 MHz, CDCl3) δ 170.5, 121.0, 120.9, 58.0,
46.5, 42.0, 37.8, 34.5, 29.0, 26.4, 25.3, 22.7, 22.4, 20.5. MS (ESI) m/z
655 [M+K]+. IR (neat) ν 2947, 2924, 2870, 2359, 1454, 1396, 1262,
1228, 1195, 730, 697 cm−1. Anal. Calcd for C28H48Cl2N4Pd: C, 54.41;
H, 7.83; N, 9.07. Found: C, 54.42; H, 7.89, N, 9.01%.
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Synthesis of 6: Compound 4 (348.5 mg, 1.0 mmol), Ag2O (116.9 mg,
0.50 mmol) and CH2Cl2 (5.0 mL) were added under an N2 atmosphere