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RSC Advances
Page 7 of 9
DOI: 10.1039/C6RA02556K
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137.0, 132.2, 129.4, 128.4, 123.9, 106.4, 39.2, 19.2. HRMS
(ESI): calcd for C23H26ClN4Pd [M-Cl]+, 499.0811; found,
499.0899. Anal. Calcd for C23H26Cl2N4Pd: C, 51.56; H, 4.89;
N, 10.46. Found: C, 51.60; H, 4.98; N, 10.26. MS (ESI): 499
[M-Cl]+. HRMS (ESI) calcd. for C23H26ClN4Pd [M-Cl]+:
499.0881; found: 499.0899. IR (neat) ν 2963, 1523, 1475,
1406, 1361, 1331, 1285, 1261, 1224, 1159, 1098, 1019,
945, 866, 797, 779, 760 cm-1.
Acknowledgements
Financial support from the National Natural Science
Foundation of China (No. 21471115) is greatly appreciated.
Quan Zhou thanks the University Students’ Innovative
Undertaking Training Program for financial support.
Notes and references
Compound 3d: yellow solid. m.p. 291 oC (decomposed).
1H NMR (CDCl3, 500 MHz, TMS) δ 7.26 (d, J = 2.5 Hz, 1H),
7.14 (d, J = 2.5 Hz, 1H), 7.08 (s, 2H), 7.06 (s, 4H), 6.05 (t, J
= 2.5 Hz, 1H), 3.78 (s, 3H), 2.39 (s, 6H), 2.35 (s, 12H). 13C
NMR (CDCl3, 125 MHz) δ 153.1, 140.5, 139.1, 136.6, 135.1,
132.1, 129.1, 124.0, 106.3, 39.2, 21.1, 19.1. MS (ESI): 527
[M-Cl]+. HRMS (ESI): calcd for C25H30ClN4Pd [M-Cl]+,
527.1214; found, 527.1195. Anal. Calcd for C25H30Cl2N4Pd:
C, 53.25; H, 5.36; N, 9.94. Found: C, 52.99; H, 5.32; N,
9.83. IR (neat) ν 3523, 2968, 2921, 2855, 1609, 1520,
1486, 1438, 1425, 1410, 1374, 1338, 1281, 1261, 1224,
1162, 1101, 1076, 1039, 992, 928, 868, 853, 801, 750 cm-1.
General procedure for the NHC-Pd(II) complex 3a
catalysed C-N coupling reactions
Under a N2 atmosphere, NHC-Pd(II) complex 3a (0.05 or
0.03 mol %), KOtBu (1.3 equiv), THF (1.0 mL), amines (0.84
mmol) and aryl chlorides (0.7 mmol) were successively
added into a sealed tube. The mixture was stirred
vigorously at the indicated temperature and specified
time shown in Tables 3-5. Then the solvent was removed
under reduced pressure and the residue was purified by
flash column chromatography (SiO2) to give the pure
products.
1
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4
5
Conclusions
In conclusion, from easily available starting materials
such as NHC.HCl, PdCl2 and 1-methylindazole and 1-
methylpyrazole, a new type of NHC-PdCl2 complexes
was obtained in acceptable to high yields in a one-pot
procedure under mild conditions, and the structures
of all of them were unambiguously determined by X-
ray single crystal diffraction. Their catalytic activity
was initially tested by the C-N coupling between
secondary and primary amines with aryl chlorides. It
was found that low catalyst loadings such as 0.03
mol% are sufficient for such transformation.
Compared to other well-defined NHC-Pd(II)
complexes such as PEPPSI-type complexes, they have
at least one of the following advantages such as easy
availability, lower cost and lower toxicity of the
ancillary ligands, and small amounts of them in the
synthesis of the complexes, easy synthesis, and lower
catalyst loading. Catalytic activities of these
complexes in other transformations are underway in
this laboratory.
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