6348 Organometallics, Vol. 29, No. 23, 2010
Xu et al.
CHarom), 7.15 (d, J = 1.8 Hz, 2H, CHimid), 7.02 (d, J = 1.8 Hz,
2H, CHimid),5.18(m,2H,CH-iPr),1.40(d,J=6.8Hz,12H,CH3-iPr).
13C NMR (CDCl3): δ 166.7, 140.5, 128.4, 127.8, 126.5, 122.5,
117.1, 52.6, 22.4. HRMS-ESI (m/z): [M þ Na]þ calcd for
C
24H28N4I2PdNa, 754.9336; found, 754.9329. Anal. Calcd
for C24H28N4I2Pd: C, 39.34; H, 3.85; N, 7.65. Found: C, 39.28; H,
3.56; N, 7.92.
Complex 8. Under an Ar atmosphere, a Schlenk flask was
chargedwithPd(OAc)2 (22.5 mg, 0.1 mmol), 6(80.8 mg, 0.2 mmol),
and dioxane (3 mL). The reaction mixture was heated to 80 °C for
7 h. After cooling to room temperature, all volatiles were removed.
The product was isolated by column chromatography using
CH2Cl2 as an eluent. Complex 8 (orange powder, 59.7 mg,
0.047 mmol, 46.9%) was obtained by recrystallization from
CH2Cl2/Et2O. 1H NMR (400 MHz, DMSO): δ7.90(d,J=7.36Hz,
4H, CHarom), 7.67 (m, 10H, CHarom), 7.50 (m, 4H, CHimid),
7.41 (m, 2H, CHarom), 5.58 (m, 2H, CHiPr), 3.24 (s, 6H,
NCH3), 1.35 (d, J = 6.8 Hz, 12H, CH3-iPr). 13C NMR
(DMSO): δ 143.4, 131.7, 131.3, 130.4, 129.1, 127.9, 124.9,
57.2, 54.9, 33.3, 21.8. HRMS-ESI (m/z): [M þ H]þ calcd for
C38H41N4Pd2I4, 1272.7584; found, 1272.7588. Anal. Calcd
for C38H40N4I4Pd2: C, 35.85; H, 3.17; N, 4.40. Found: C,
35.89; H, 2.95; N, 4.56.
Figure 5. Comparison of reaction progress with complexes
7-11.
Table 5. Suzuki-Miyaura Coupling with NHC-Pd Complexesa,b
Complex 9. Ag2O (3.6 mg, 0.016 mmol) and 6 (13.0 mg, 0.032
mmol) were combined in a Schlenk flask with CH2Cl2 (1 mL)
under Ar. The mixture was stirred at room temperature for 4 h.
The solution was filtrated through Celite and mixed with
complex 8 (20.0 mg, 0.016 mmol). After stirring for 5 h at room
temperature, the product was separated by column chromatog-
raphy using CH2Cl2 as an eluent. Complex 9 (light yellow
powder, 19.2 mg, 0.021 mmol, 65.8%) was obtained by recrys-
1
tallization from CH2Cl2/Et2O. H NMR (400 MHz, CDCl3):
δ 7.97 (m, 4H, CHarom), 7.54 (m, 6H, CHarom), 7.42 (m, 8H,
CHarom), 7.31 (m, 2H, CHarom), 5.38 (m, 2H, CHiPr), 3.19 (s, 6H,
CH3), 1.35 (d, J = 6.8 Hz, 12H, CH3-iPr). 13C NMR (CDCl3): δ
145.2, 141.9, 134.2, 132.2, 131.5, 131.0, 130.9, 128.9, 127.6,
126.9, 55.8, 32.8, 23.2. HRMS-ESI (m/z): [M þ Na]þ calcd for
C38H40N4I2PdNa, 935.0275; found, 935.0303. Anal. Calcd for
entry
precatalyst
A
B
1
2
3
4
5
7
8
9
10
11
40
52
84
35
62
13
<0.1
<0.1
7
C40H44N4Cl4I2Pd (9 2CH2Cl2) C, 44.37; H, 4.10; N, 5.17.
3
Found: C, 44.29; H, 4.17; N, 5.21.
Complex 10. A Schlenk flask was charged with Pd(OAc)2
(90.0 mg, 0.4 mmol), 5 (125.6 mg, 0.4 mmol), K2CO3 (276.0 mg,
2.0 mmol), KI (66.4 mg, 0.4 mmol), and 3-chloropyridine (2 mL)
under Ar. The reaction mixture was heated to 80 °C for 16 h.
After cooling to room temperature, 3-chloropyridine was evap-
orated under vacuum. The residue was dissolved in CH2Cl2 and
filtered through Celite. After evaporation of all volatiles, the
residue was washed with pentane and complex 10 was obtained
(yellow solid, 263 mg, 0.4 mmol, 100%). 1H NMR (400 MHz,
CDCl3): δ 8.80 (d, J = 1.24 Hz, 1H), 8.78 (d, J = 1.24 Hz, 1H),
8.02 (m, 2H), 7.70 (m, 1H), 7.67 (m, 2H), 7.52 (m, 1H), 7.24 (d,
J = 2.0 Hz, 1H), 7.22 (m, 2H), 5.71 (m, J = 6.76 Hz, 1H), 1.64
(d, J = 6.8 Hz, 6H). 13C NMR (CDCl3): δ 152.7, 151.7, 143.8,
139.9, 137.5, 132.2, 129.0, 128.8, 126.5, 124.6, 124.1, 118.1,
53.8, 22.4. HRMS-ESI (m/z): [M þ H]þ calcd for C17H19-
ClI2N3Pd, 659.8392; found, 659.8446. Anal. Calcd for C17H18-
ClI2N3Pd C, 30.94; H, 2.75; N, 6.37. Found: C, 31.25; H, 2.94;
N, 6.27.
Complex 11. A Schlenk flask was charged with complex 8
(95.0 mg, 0.075 mmol) in dichloromethane (2 mL) under Ar, and
then 3-chloropyridine (17.0 mg, 0.15 mmol) was added. The
reaction mixture was stirred at room temperature for 2 h. All
volatiles were removed in vacuo. The residue was washed with
pentane, and complex 11 was obtained (yellow solid, 112.2 mg,
0.15 mmol, 100%). 1H NMR (400 MHz, CDCl3): δ 8.96 (d, J =
2.28 Hz, 1H), 8.87 (m, 1H), 7.93 (m, 2H), 7.61 (m, 4H), 7.49 (m,
5H), 7.17 (m, 1H), 5.97 (m, J = 8.24 Hz, 1H), 3.20 (s, 3H), 1.49
(d, J = 7.32 Hz, 6H). 13C NMR (CDCl3): δ 152.9, 151.9, 143.0,
137.2, 133.2, 132.0, 131.8, 131.5, 130.8, 129.4, 128.6, 128.5,
126.1, 124.5, 117.3, 58.2, 33.4, 22.7. HRMS-ESI (m/z): [M þ H]þ
<0.1
a Pd complex (2.5 mol %), Cs2CO3 (2 equiv), aryl halide (1.0 equiv),
boronic acid (1.5 equiv), dioxane, 80 °C, 24 h. b Isolated yield, average of
at least two runs.
was performed by a Waters Q-Tof Premier Micromass instrument,
using electrospray ionization (ESI) mode.
General Procedure for the in Situ NHC-Pd-Catalyzed Suzu-
ki-Miyaura Coupling Reactions (2.5 mol % catalyst loading).
Pd(OAc)2 (2.8 mg, 0.0125 mmol), NHC precursor (0.025 mmol),
Cs2CO3 (326 mg, 1 mmol), and dioxane (2 mL) were placed in an
oven-dried Schlenk flask under an argon atmosphere. The
Schlenk tube was heated to 80 °C in an oil bath. After 30 min
of heating, boronic acid (0.75 mmol) and aryl halide (0.5 mmol)
in 2 mL of dioxane were added into the flask at room tempera-
ture. The reaction mixture was heated to 80 °C under an argon
atmosphere for 24 h. After cooling to room temperature,
volatiles were removed in vacuo. The residue was purified by
silica gel flash column chromatography. All the products were
identified by spectral comparison with literature data or with
analogous literature data.
Complex 7. Under an Ar atmosphere, a Schlenk flask was
charged with Pd(OAc)2 (22.5 mg, 0.1 mmol), 5(62.8 mg, 0.2 mmol),
and dioxane (3 mL). The reaction mixture was heated to 80 °C
for 6 h. After cooling to room temperature, the product was purified
by column chromatography with CH2Cl2 as an eluent. Complex 7
(light yellow powder, 51.2 mg, 0.070 mmol, 70.1%) was obtained by
recrystallization with CH2Cl2/Et2O. 1H NMR (400 MHz, CDCl3):
δ 7.98 (m, 4H, CHarom), 7.50 (m, 4H, CHarom), 7.41(m, 2H,