Full Paper
ed transition state for the conversion of [3H]Cl to 5 revealed
that, unlike CMD or AMLA reactions of (hetero)arenes involving
Pd acetate complexes, the acetate ligand plays the dominant
role in this a-C(sp3)ÀH activation. This C(sp3)ÀH activation is
a direct and exceptionally mild method for the formation of
metal ylide complexes; we are currently pursuing applications
of this reaction in (asymmetric) catalysis.
Synthesis of rac-[Cp*Ir(1a)Cl2] (2a)
Sodium acetate (62 mg, 0.75 mmol) was added to a solution of
[Cp*IrCl2]2 (100 mg, 0.126 mmol) in CH2Cl2 (14 mL), which was then
stirred at RT for 20 min. After this time, pyridiniumium salt [1aH]Cl
(51 mg, 0.25 mmol) was added to the reaction mixture, which was
stirred for a further 45 min. After this time, the volatiles were re-
moved in vacuo to give an orange/yellow solid. The solid was
scraped from the sides of the flask and washed with Et2O (12ꢂ
10 mL). The solid was extracted in MeCN (3 mL), and the solution
was dried by passing it through a pipette containing K2CO3; this
extraction was repeated twice. Finally, the volatiles were removed
in vacuo to give 2a as a yellow solid (98 mg, 69%). 1H NMR
(400 MHz, CDCl3): d=1.31 (3H, t, J=7.1, OCH2CH3), 1.61 (15H, s,
Experimental Section
All manipulations were performed under dry, oxygen-free nitrogen
by using standard Schlenk techniques, unless otherwise stated.
CH2Cl2 was dried by passing through a column of activated alumi-
na and then degassed. [Cp*IrCl2]2 and 1-mesityl imidazole were
prepared as reported in the literature.[23,24] NaOAc was dried in an
oven at 808C overnight before use. All other reagents were ob-
tained from Sigma–Aldrich, Johnson Matthey or Alfa Aesar and
used as supplied. NMR spectra were recorded on a Bruker DRX400
spectrometer at 298 K; chemical shifts have been referenced to the
residual protonated solvent peak, and J values are given in Hz. For
some compounds, assignments for 1H and 13C NMR peaks were
2
3
2
C5Me5), 4.11 (1H, dq, J=10.8, J=7.1, OCH2CH3), 4.35 (1H, dq, J=
3
10.8, J=7.1, OCH2CH3), 6.75 (1H, s, HCÀIr), 7.58 (2H, app t, J=6.9,
PyCH), 7.85 (1H, tt, 3J=7.7, 4J=1.3, PyCH), 8.66 (2H, d, J=6.7,
PyCH); 13C{1H} NMR (100.6 MHz, CDCl3): d=8.7 (C5Me5), 14.7
(OCH2CH3), 55.5 (HCÀIr), 60.8 (OCH2CH3), 86.4 (C5Me5), 124.5 (Py-
C3,5), 139.8 (Py-C4), 145.1 (Py-C2,6), 175.05 ppm (C=O); IR (solid):
u˜ =1709 cmÀ1 (C=O); MS (FAB): m/z (%): 563 (16) [M]+, 528 (100)
[MÀCl]+; elemental analysis calcd (%) for C19H26NO2IrCl2 (563.54): C
40.49, H 4.65, N 2.49; found: C 40.52, H 4.60, N 2.52.
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aided by H–1H COSY, H–1H NOESY and H–13C HMQC 2D NMR ex-
periments. FTIR spectra were run in a diamond ATR cell by using
a Perkin–Elmer Spectrum 1 instrument. ESI mass spectra were re-
corded on a micromass Quattra LC spectrometer in MeCN/MeOH
with a cone voltage of +25 V; FAB mass spectra were obtained on
a Kratos concept spectrometer by using NBA as the matrix. Ele-
mental analyses were performed at London Metropolitan Unive-
rsity.
Synthesis of rac-[Cp*Ir(1b)Cl2] (2b)
Sodium acetate (52 mg, 0.64 mmol) was added to a solution of
[Cp*IrCl2]2 (85 mg, 0.106 mmol) in CH2Cl2 (12 mL), which was then
stirred at RT for 20 min. After this time, pyridinium chloride salt
[1aH]Cl (50 mg, 0.21 mmol) was added to the reaction mixture,
which was stirred for a further 45 min. After this time, the volatiles
were removed in vacuo to give an orange yellow solid. The solid
was scraped from the sides of the flask and washed with Et2O (10ꢂ
10 mL). The solid was extracted in MeCN (2ꢂ9 mL), and the solu-
tion was dried by passing it through a pipette containing K2CO3;
this extraction was then repeated once. Finally, the volatiles were
removed in vacuo to give 2b as an orange solid (92 mg, 73%).
Crystals of 2b suitable for structure determination by X-ray diffrac-
tion were obtained by diffusion of n-pentane into a CH2Cl2 solution
Synthesis of [1aH]Cl
A solution of pyridine (1.50 mL, 18.6 mmol) and ethyl chloroacetate
(2 mL, 18.6 mmol) in Et2O (5 mL) was heated at 408C for 16 h. The
resulting brown precipitate was isolated by filtration and washed
with Et2O (2ꢂ5 mL), giving [1aH]Cl as a brown solid (2.16 g, 58%).
1H NMR (400 MHz, CDCl3): d=1.33 (3H, t, J=7.1, CH2CH3), 4.29 (2H,
q, J=7.1, CH2CH3), 6.50 (2H, s, CH2CO2Et), 8.07 (2H, app t, J=7.1,
PyCH), 8.50 (1H, t, J=7.8, PyCH), 9.59 ppm (2H, d, J=5.4, PyCH);
13C{1H} NMR (100.6 MHz, CDCl3): d=14.04 (OCH2CH3), 61.0 (CH2),
63.3 (CH2), 127.5 (Py-C3,5), 145.6 (Py-C4), 147.1 (Py-C2,6), 166.20
(C=O); MS (ESI) m/z (%): 166 (50) [MÀCl]+, 138 (100) [MÀClÀEt+
H]+.
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of 2b. H NMR (400 MHz, CDCl3): d=1.31 (3H, t, J=7.2, OCH2CH3),
1.61 (15H, s, C5Me5), 4.12 (1H, dq, J=10.7, J=7.2, OCH2CH3), 4.35
(1H, dq, J=10.7, J=7.2, OCH2CH3), 6.72 (1H, s, HC-Ir), 7.53 (1H, dd,
J=8.3, J=6.3, Py-5-CH), 7.80 (1H, ddd, J=8.3, J=2.0, 1.1, Py-4-CH),
8.61 (1H, app dt, J=6.3, J=1.1, Py-6-CH), 8.65 ppm (1H, app t, Py-
2-CH); 13C{1H} NMR (100.6 MHz, CDCl3): d=7.1 (C5Me5), 13.1
(OCH2CH3), 54.2 (HCÀIr), 59.1 (OCH2CH3),84.8 (C5Me5), 123.0 (Py C5),
130.5 (Py C3), 137.6 (Py C4), 141.1 (Py C6), 142.4 (Py C2), 172.9 ppm
(C=O); IR (solid): u˜ =1712 cmÀ1 (C=O); MS (ESI): m/z (%): 562 (100)
[MÀCl]+; elemental analysis calcd (%) for C19H25IrNO2Cl3: C 38.16, H
4.21, N 2.34; found: C 38.15, H 3.95, N 2.29.
Synthesis of [1bH]Cl
A mixture of 3-chloropyridine (0.44 mL, 4.7 mmol) and ethyl chlor-
oacetate (0.50 mL, 4.7 mmol) was heated at 908C for 64 h. The re-
sulting brown residue was extracted with CHCl3 (3ꢂ10 mL). The
volatiles were then removed in vacuo, and the oily residue washed
with Et2O (3ꢂ5 mL). The residue was dried in vacuo to give
Synthesis of [3H]Cl
A solution of 1-mesityl imidazole (0.97 g, 5.3 mmol) and ethyl
chloroacetate (0.70 mL, 6.4 mmol) in MeCN (8 mL) was heated at
908C for 12 h. The solution was cooled to RT, and the volatiles
were removed in vacuo. The resulting solid was washed with Et2O
(3ꢂ5 mL) to give [3H]Cl as a white solid (1.59 g, 96%). 1H NMR
(400 MHz, CDCl3): d=1.26 (3H, t, J=7.2, CH2CH3), 2.03 (6H, s, o-
CH3), 2.28 (3H, s, p-CH3), 4.21 (2H, q, J=7.2, CH2CH3), 5.88 (2H, s,
NCH2CO2Et), 6.94 (2H, s, Mes-CH), 7.08 (1H, t, J=1.7, NCHCHN),
7.80 (1H, t, J=1.7, NCHCHN), 10.45 ppm (1H, t, J=1.4, N2CH);
13C{1H} NMR (100.6 MHz, CDCl3): d=14.0 (CH2CH3), 17.5 (o-CH3),
21.1 (p-CH3), 50.6 (CH2), 62.7 (CH2), 122.4 (NCHCHN), 124.7
1
[1bH]Cl as a brown solid (0.687 g, 62%). H NMR (400 MHz, CDCl3):
d=1.30 (3H, t, J=7.2, CH2CH3), 4.27 (2H, q, J=7.2, CH2CH3), 6.51
(2H, s, CH2CO2Et), 8.13 (1H, dd, J=8.4, 6.1, PyCH), 8.47 (1H, dd, J=
8.4, 0.7, PyCH), 9.71 (1H, d, J=6.1, PyCH), 9.76 ppm (1H, s, PyCH);
13C{1H} NMR (100.6 MHz, CDCl3): d=13.9 (OCH2CH3), 60.7 (CH2), 63.2
(CH2), 128.2 (Py-CH), 125.0 (PyÀCCl), 145.6, 145.8, 145.9, (PyÀCH),
166.20 (C=O); MS (ESI) m/z (%): 200 (88) [MÀCl]+, 172 (100)
[MÀClÀEt+H]+.
Chem. Eur. J. 2014, 20, 1 – 8
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