CHEN ET AL.
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Sigma-Aldrich, Acros, Merck, TEDIA, and Alfa-Aesar of
USA. The imidazolium salts IPrꢀHCl and SIPrꢀHCl and
NHC–palladium complexes were prepared following lit-
erature procedures, and their identity and purity were
confirmed using 1H NMR spectroscopy.[17]
All aryl halides and boronic acids were used as
received. Technical-grade ethyl alcohol was used to carry
out the Suzuki–Miyaura cross-coupling reactions. Flash
chromatography was performed on silica gel 60 (230–400
mesh) using mixtures of hexane/ethyl acetate (10:1)
unless otherwise noted.
2 ml chloroform as solvents. The desired compound was
obtained as a pale yellow solid in 93% yield (372 mg). H
1
NMR (CDCl3, 400 MHz) δ 1.23(d, 12H, J = 4 Hz,
CH(CH3)2), 1.52(d, 12H, J = 4 Hz, CH(CH3)2), 2.62(s, 9H,
NH(CH3)3), 3.51(sep, 4H, J = 6.67 Hz, CH(CH3)2), 4.00(s,
4H, CH2), 7.28(d, 4H, J = 4 Hz, ArH), 7.39(t, 2H,
J = 8 Hz, ArH), 10.40(s, 1H, NH). 13C{1H} NMR (CDCl3,
75 MHz) δ 24.3(s, CH(CH3)2), 26.7(s, CH(CH3)2), 28.7(s,
CHiPr), 45.1(s, N (CH3)3), 53.6(s, CH2), 124.4(s, CH aro-
matic), 129.2(s, C aromatic), 135.7(s, C aromatic), 148.1(s,
C
aromatic), 185.7(s, Ccarbene). Anal. Calcd for
1H and 13C{1H} NMR spectra were recorded either on
Bruker-AV-300 or Bruker-AV-400 spectrometers in
chloroform-d at ambient temperature unless stated other-
wise and referenced internally to the residual solvent
peak and reported as parts per million relative to tetra-
methylsilane. Elemental analyses were performed using a
Heraeus CHN-O rapid analyzer or a FLASH 2000 Series
Nitrogen and Carbon Analyzer instrument (Thermo).
The Suzuki–Miyaura cross-coupling reactions were ana-
lyzed using gas chromatography–mass spectrometry
(GC–MS) on a Bruker SCION 436 SQ instrument
equipped with a Bruker BR-5 ms column. The MS detec-
tor was configured with an electronic impact ionization
source.
C30H48Cl3N3Pd: C, 54.31; H, 7.29; N, 6.33. Found: C,
54.14; H, 7.45; N, 6.47.
2.1.3 | Synthesis of 2a
The procedure for the preparation of 2a was similar to
that used for 1a, but here a vial was charged with
[Pd(μ-Cl)Cl(IMes)]2 (289 mg, 0.3 mmol) and
trimethylamine hydrochloride (57 mg, 0.6 mmol) and
2 ml chloroform as solvents. The desired compound was
1
obtained as a pale yellow solid in 84% yield (290 mg). H
NMR (CDCl3, 400 MHz) δ 2.31(s, 12H, CH3), 2.35(s, 6H,
CH3), 2.66(s, 9H, NH(CH3)3), 7.00(d, 2H, J = 8 Hz,
CH=CH + ArH), 9.92(s, 1H, NH). 13C{1H} NMR (CDCl3,
75 MHz) δ 19.1(s, CH3), 21.1(s, CH3), 45.3(s, NH(CH3)3),
124.0(s, CH), 129.0(s, CH aromatic), 135.4(s, C aromatic),
136.8(s, C aromatic), 139.0(s, C aromatic), 150.5(s,
Ccarbene). Anal. Calcd for C24H34Cl3N3Pd: C, 49.93; H,
5.94; N, 7.28. Found: C, 50.03; H, 6.03; N, 7.06.
2.1.1 | Synthesis of 1a
A vial was charged with [Pd(μ-Cl)Cl(IPr)]2 (340 mg,
0.3 mmol) and trimethylamine hydrochloride (57 mg,
0.6 mmol) and chloroform (2 ml) as solvents. The solu-
tion was heated at 50ꢁC, stirred for 15 h. It was then fil-
tered through a pad of celite, and the filtrate was
removed from the solvent to produce a pale yellow solid,
to obtain the desired compound in 98% yield (389 mg). 1H
NMR (CDCl3, 400 MHz) δ 1.07(d, 12H, J = 8 Hz,
CH(CH3)2), 1.43(d, 12H, J = 4 Hz, CH(CH3)2), 2.66(s, 9H,
NH(CH3)3), 3.11(sep, 4H, J = 6.7 Hz, CH(CH3)2), 7.06(s,
2H, CH=CH), 7.32(d, 4H, J = 8 Hz, ArH), 7.47(t, 2H,
J = 8 Hz, ArH), 10.60(s, 1H, NH). 13C{1H} NMR (CDCl3,
75 MHz) δ 23.3(s, CH(CH3)2), 26.2(s, CH(CH3)2), 28.7(s,
CHiPr), 45.1(s, N (CH3)3), 124.0(s, CH), 124.9(s, CH aro-
matic), 130.0(s, C aromatic), 135.5(s, C aromatic), 147.2(s,
2.1.4 | Synthesis of 2b
The procedure for the preparation of 2b was similar to
that used for 1a, but here a vial was charged with
[Pd(μ-Cl)Cl(SIMes)]2 (288 mg, 0.3 mmol) and
trimethylamine hydrochloride (57 mg, 0.6 mmol) and
2 ml chloroform as solvents. The desired compound was
1
obtained as a pale yellow solid in 87% yield (304 mg). H
NMR (CDCl3, 400 MHz) δ 2.30(s, 12H, CH3), 2.52(s, 12H,
CH3), 2.65(s, 9H, NH(CH3)3), 3.97(s, 4H, CH2), 6.94(s,
4H, ArH), 10.20(s, 1, NH). 13C{1H} NMR (CDCl3,
75 MHz) δ 19.4(s, CH3), 21.0(s, CH3), 45.2(s, N (CH3)3),
50.9(s, CH2), 129.3(s, CH aromatic), 135.2(s, C aromatic),
137.6(s, C aromatic), 138.2(s, C aromatic), 183.9(s,
Ccarbene). Anal. Calcd for C24H36Cl3N3Pd: C, 49.76; H,
6.26; N, 7.25. Found: C, 49.85; H, 6.39; N, 7.14.
C
aromatic), 154.3(s, Ccarbene). Anal. Calcd for
C30H46Cl3N3Pd: C, 54.47; H, 7.01; N, 6.35. Found: C,
54.02; H, 6.95; N, 6.85.
2.1.2 | Synthesis of 1b
The procedure for the preparation of 1b was similar to
that used for 1a, but here a vial was charged with
[Pd(μ-Cl)Cl(SIPr)]2 (341 mg, 0.3 mmol) and
trimethylamine hydrochloride (57 mg, 0.6 mmol) and
2.1.5 | Synthesis of 3
A vial was charged with 1a (258 mg, 0.39 mmol) and
excess Na2CO3 (0.5 g, 4.72 mmol) and 4 ml deionized