Carbenes Made Easy: Formation of Unsymmetrically Substituted N-Heterocyclic Carbene Complexes
under reduced pressure and the solid was dissolved in DCM
(20 mL). The solution was extracted with a saturated solu-
tion of NH4Cl (20 mL). The organic layer was dried with
Na2SO4 and the solvent was removed under reduced pres-
sure. The crude product was dissolved in a minimum of
DCM and covered with a layer diethyl ether, inducing crys-
tallization of the NHC-Pd(II) complexes as colourless crys-
tals. The crystals were filtered off, washed with diethyl ether
and dried under reduced pressure. All the complexes are air
and moisture stable compounds and can be stored at room
temperature without decomposition.
Synthesis of 10: Colourless crystals; yield: 148 mg (85%);
1H NMR (300 MHz, DMSO): d=2.06 (s, 3H, CH3), 2.30 (s,
6H, CH3), 2.44 (s, 3H, CH3), 3.52 (s, 3H, CH3), 3.98 (m,
4H, CH2), 7.25 (m, 6H, ArH); 13C NMR (75 MHz, DMSO):
d=17.35, 17.93 (2C), 18.68, 37.20, 51.05, 51.20, 128.31,
128.42 (2C), 128.93, 129.06 (2C), 130.68, 135.33 (2C),
135.62, 136.77, 137.71, 182.03; IR (KBr): n=3443, 2951,
2919, 2195, 1631, 1541, 1491, 1473, 1411, 1383, 1317, 1276,
1116, 780, 734, 619 cmÀ1; HR-MS (FAB+): m/z=460.0763,
calcd. for C21H25N3ClPd [MÀClÀ]+: 460.0772.
1034, 998, 780, 701 cmÀ1; HR-MS (FAB+): m/z=604.1722,
calcd. for C32H37ClN3Pd [MÀClÀ]+: 604.1711.
Synthesis of 14: Colourless solid; yield: 170 mg (308 mmol,
96%); 1H NMR (300 MHz, CD2Cl2): d=1.32 (d, 3H, J=
6.9 Hz, CH3), 1.37 (d, 3H, J=6.6 Hz, CH3), 1.95 (s, 3H,
CH3), 2.22 (s, 6H, CH3), 2.25 (s, 3H, CH3), 2.26 (s, 3H,
CH3), 2.41 (s, 3H, CH3), 3.71–3.92 (m, 4H, CH2), 5.38 (m,
1H, J=6.8 Hz, CH), 6.73 (s, 1H, ArH), 6.90 (s, 2H, ArH),
7.00 (s, 1H, ArH); 13C NMR (75 MHz, CD2Cl2): d=18.37,
19.14 (2C), 19.67, 20.50, 21.27, 21.58, 21.88, 43.86, 51.42,
52.53, 129.69 (2C), 129.75, 131.02, 135.09, 135.56, 136.25
(2C), 138.54, 139.96, 141.77, 184.74; IR (KBr): n=2971,
2193, 1608, 1510, 1458, 1382, 1314, 1271, 1197, 1105, 1058,
855, 713, 625, 599, 573, 460, 428 cmÀ1; HR-MS (FAB+):
m/z=516.1391, calcd. for C25H33ClN3Pd [MÀClÀ]+: 516.1398.
Synthesis of 15: Colourless solid; yield: 170 mg (266 mmol,
83%); 1H NMR (300 MHz, CD2Cl2): d=1.05 (d, 3H, J=
6.8 Hz, CH3), 1.07 (d, 3H, J=6.8 Hz, CH3), 1.13 (d, 3H, J=
6.8 Hz, CH3), 1.19 (d, 6H, J=6.8 Hz, CH3), 1.21 (d, 6H, J=
6.8 Hz, CH3), 1.36 (d, 6H, J=6.7 Hz, CH3), 1.46 (d, 3H, J=
6.7 Hz, CH3), 2.88 (m, 1H, J=6.8 Hz, CH), 3.24 (m, 3H,
CH), 3.71–4.01 (m, 4H, CH2), 5.47 (dm, 1H, J=7.0, 6.6 Hz,
CH), 7.18, 7.17 (dd, 1H, J=7.7, 1.4 Hz, ArH), 7.19 (d, 2H,
J=7.7 Hz, ArH), 7.29 (dd, 1H, J=7.8, 1.7 Hz, ArH), 7.40
(m, 2H, ArH); 13C NMR (75 MHz, CD2Cl2): d=20.65,
21.17, 23.49 (2C), 23.63, 23.87, 24.51, 27.22, 27.26, 29.29,
29.54, 30.36, 43.67, 53.03, 54.47, 124.73 (2C), 125.01, 126.19,
130.76, 131.80, 134.57, 146.85, 146.96 (2C), 149.31, 185.97;
IR (KBr): n=2965, 2930, 2870, 2185, 1497, 1459, 1433, 1386,
1366, 1348, 1331, 1315, 1267, 1184, 1113, 1058, 806, 751,
Synthesis of 11: Colourless solid; yield: 150 mg (286 mmol,
89%); 1H NMR (600 MHz, CD2Cl2): d=1.34 (d, 3H, J=
6.8 Hz, CH3), 1.39 (d, 3H, J=6.7 Hz, CH3), 2.01 (s, 3H,
CH3), 2.27 (s, 6H, CH3), 2.47 (s, 3H, CH3), 3.82–3.91 (m,
4H, CH2), 5.40 (m, 1H, J=6.9, 6.3 Hz, CH), 6.94 (dd, 1H,
J=7.3, 1.9 Hz, ArH), 7.1 (d, 2H, J=7.6 Hz, ArH), 7.17–7.27
(m, 3H, ArH); 13C NMR (125 MHz, CD2Cl2): d=18.11,
18.92 (2C), 19.40, 20.13, 20.93, 43.61, 51.02, 52.25, 128.65
(2C), 128.70, 129.62, 130.01, 130.70, 135.64, 136.19 (2C),
137.30, 138.70,184.22; 15N NMR (600 MHz, CD2Cl2, urea):
d=131.78, 148.43, 171.32; IR (KBr): n=2970, 2925, 2358,
2195 (NC), 1633, 1509, 1467, 1368, 1314, 1271, 1192, 1127,
1102, 1056, 935, 782, 623, 602, 569 cmÀ1; HR-MS (FAB+):
m/z=488.1104, calcd. for C23H29ClN3Pd [MÀClÀ]+: 488.1085.
Synthesis of 12: Colourless solid; yield: 133 mg (250 mmol,
628 cmÀ1
;
HR-MS (FAB+): m/z=600.2335, calcd. for
C31H45ClN3Pd [MÀClÀ]+: 600.2337.
Synthesis of 16: Colourless solid; yield: 170 mg (266 mmol,
95%); 1H NMR (500 MHz, CD2Cl2): d=1.03 (d, 3H, J=
6.9 Hz, CH3), 1.04 (d, 3H, J=6.9 Hz, CH3), 1.11 (d, 3H, J=
6.9 Hz, CH3), 1.17 (d, 6H, J=6.8 Hz, CH3), 1.20 (d, 6H, J=
6.8 Hz, CH3), 1.34 (d, 3H, J=6.7 Hz, CH3), 1.42–1.73 (m,
6H, CH2), 1.85 (m, 3H, CH2), 2.32 (m, 1H, CH2), 2.86 (m,
1H, J=6.8 Hz, CH), 3.21 (m, 2H, J=6.9 Hz, CH), 3.27 (m,
1H, CH), 3.67–3.96 (m, 4H, CH2), 4.93 (tt, 1H, J=11.4,
3.7 Hz, CH), 7.15 (m, 1H, ArH), 7.18 (d, 2H, J=7.8 Hz,
ArH), 7.28 (dd, 1H, J=7.8, 1.4 Hz, ArH), 7.39 (m, 2H,
ArH); 13C NMR (75 MHz, CD2Cl2): d=23.08 (2C), 23.21,
23.53 (2C), 24.13, 25.54, 25.66, 25.83, 26.84, 26.88, 28.89,
29.15, 30.03 (2C), 30.74, 31.72, 44.59, 54.15, 60.20, 124.35
(2C), 124.59, 125.79, 130.35, 131.40, 134.28, 146.54 (2C),
147.47, 148.96, 185.59; IR (KBr): n=2963, 2931, 2867, 2188,
1589, 1500, 1458, 1386, 1365, 1336, 1304, 1269, 1184, 1111,
1055, 804, 750, 731, 626 cmÀ1; HR-MS (FAB+): m/z=
640.2672, calcd. for C34H49ClN3Pd [MÀClÀ]+: 640.2650.
Synthesis of 17: Colourless solid; yield: 170 mg (266 mmol,
95%); 1H NMR (300 MHz, CDCl3): d=1.0 (d, 3H, J=
6.8 Hz, CH3), 1.02 (d, 3H, J=6.9 Hz, CH3), 1.07 (d, 3H, J=
6.9 Hz, CH3), 1.17 (d, 6H, J=6.9 Hz, CH3), 1.19 (d, 6H, J=
6.9 Hz, CH3), 1.4 (d, 3H, J=6.4 Hz, CH3), 1.69 (m, 6H,
CH2), 2.23 (m, 3H, CH), 2.43 (m, 3H, CH, CH2), 2.74 (m,
3H, CH, CH2), 2.86 (m, 1H, J=6.8 Hz, CH), 3.24 (m, 2H,
J=6.8 Hz, CH), 3.36 (m, 1H, CH), 3.66–4.01 (m, 4H, CH2),
7.06 (dd, 1H, J=7.8, 1.7 Hz, ArH), 7.12 (d, 2H, J=7.8 Hz,
ArH), 7.25 (dd, 1H, J=7.8, 1.7 Hz, ArH), 7.33 (td, 2H, J=
7.9, 2.8 Hz, ArH); 13C NMR (75 MHz, CDCl3): d=23.09,
23.33 (2C), 23.57 (2C), 24.14, 27.01, 27.10, 28.94, 29.16 (2C),
1
78%); H NMR (300 MHz, CD2Cl2): d=0.98–1.86 (m, 10H,
CH2), 1.98 (s, 3H, CH3), 2.23 (s, 6H, CH3), 2.44 (s, 3H,
CH3), 3.81 (m, 4H, CH2), 4.87 (tt, 1H, J=10.7, 3.8 Hz, CH)
6.9 (dd, 1H, J=6.6 Hz, ArH), 7.07 (d, 2H, J=8.4 Hz, ArH),
7.12 (m, 3H, ArH); 13C NMR (75 MHz, CD2Cl2): d=18.49,
19.23 (2C), 19.80, 25.91, 26.04, 26.12, 31.18, 32.07, 45.24,
51.33, 60.10, 129.02 (2C), 129.06, 129.99, 130.38, 131.05,
136.04, 136.57 (2C), 137.76, 139.11, 184.56; IR (KBr): n=
2931, 2855, 2193 (NC), 1632, 1510, 1454, 1380, 1333, 1300,
1272, 1170, 1100, 1032, 990, 894, 780, 623, 570 cmÀ1; HR-MS
(FAB+): m/z=530.1397, calcd. for C26H33ClN3Pd [MÀClÀ]+:
530.1398.
Synthesis of 13: Yellow solid; yield: 100 mg (157 mmol,
49%, mixture of diastereoisomers); 1H NMR (300 MHz,
CD2Cl2): d=1.05–1.81 (m, 10H, CH2), 1.92 (s, CH3), 2.06 (s,
CH3), 2.17 (s, CH3), 2.39 (s, CH3), 2.55 (s, CH3), 4.03 (dd,
J=11.3, 5.6 Hz, CH2), 4.15 (dd, J=11.3, 6.0 Hz, CH2), 4.33
(t, J=11.3 Hz, CH2), 4.88 (dd, J=11.8, 5.6 Hz, CH), 5.03
(dd, J=11.6, 6.0 Hz, CH), 5.16 (m, 1H, CH), 6.73 (m, 1H,
ArH), 6.96–7.32 (m, 10H, ArH); 13C NMR (75 MHz,
CD2Cl2): d=18.27, 18.51, 18.81, 19.08, 19.71, 19.87, 25.10,
25.44, 25.48, 30.24, 30.75, 31.38, 31.77, 50.75, 52.29, 59.58,
59.99, 66.51, 66.56, 77.44, 127.98, 128.01, 128.30, 128.49,
129.07, 129.20, 129.27, 129.57, 129.68, 129.90, 130.36, 130.45,
183.36, 183.98; IR (KBr): n=3031, 2932, 2855, 2193, 1631,
1509, 1474, 1453, 1416, 1382, 1296, 1250, 1210, 1168, 1101,
Adv. Synth. Catal. 2010, 352, 3001 – 3012
ꢃ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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