(d, J = 7.0 Hz, 4H, Ph), 7.26–7.17 (m, 6H, Ph), 7.13 (d, J = 8.1
Hz, 4H, NAr), 6.81 (d, J = 7.8 Hz, 4H, NAr), 6.46 (t, J = 7.7
Hz, 1H, central Ar (4)), 6.24 (d, J = 7.7 Hz, 2H, central Ar (3,5)),
4.44–4.39 (m, 2H, NCH), 4.10 (app t, J = 10.0 Hz, 2H, NCHH),
3.78 (dd, J = 3.1, 9.9 Hz, 2H, NCHH), 3.40 (dd, J = 3.0, 13.3 Hz,
2H, CHHPh), 3.07 (dd, J = 7.9, 13.3 Hz, 2H, CHHPh), 2.36 (s,
6H, CH3). 13C NMR (100 MHz, CDCl3): d 177.9, 167.5, 137.9,
137.3, 136.5, 132.8, 130.1, 129.9, 128.2, 126.2, 125.5, 124.3, 121.7,
60.9, 58.9, 41.1, 21.1. Anal. calcd for C40H37ClN4Ni: C, 71.93; H,
5.58; N, 8.39. Found: C, 71.79; H, 5.80; N, 8.27%.
7.09 (d, J = 8.1 Hz, 4H, NAr), 6.52 (t, J = 7.7 Hz, 1H, central Ar
(4)), 6.25 (d, J = 7.7 Hz, 2H, central Ar (3,5)), 4.10 (app t, J = 10.2
Hz, 2H, NCHH), 4.03–4.00 (m, 2H, NCH), 3.81 (dd, J = 3.4,
9.7 Hz, 2H, NCHH), 2.55 (br s, 3H, CH3CN), 2.40 (s, 6H, CH3),
2.10 (br s, 2H, CH(CH3)2), 0.95 (d, J = 5.2 Hz, 12H, CH(CH3)2).
13C NMR (100 MHz, CDCl3): d 173.7, 167.1, 137.9, 136.3,
132.8, 130.2, 125.7, 124.8, 122.6, 63.6, 55.4, 31.1, 21.2, 18.2, 14.6,
2.9.
Cationic Ni(Phebim) complex 3c
88% isolated yield. mp: 191–193 ◦C. [a]D20 +234 (c 0.09 in CH2Cl2).
IR(KBr): nmax/cm-1 3026, 2938, 2679, 2490, 1577, 1539, 1511,
1430, 1302, 1158, 1088, 1055, 823, 706, 517. 1H NMR (400 MHz,
CDCl3): d 7.47 (d, J = 6.9 Hz, 4H, Ph), 7.29–7.24 (m, 6H, Ph),
7.10 (d, J = 8.2 Hz, 4H, NAr), 6.66 (br s, 4H, NAr), 6.47 (t, J = 7.6
Hz, 1H, central Ar (4)), 6.11 (d, J = 8.0 Hz, 2H, central Ar (3,5)),
4.35–4.33 (m, 2H, NCH), 4.27 (app t, 2H, J = 10.0 Hz, NCHH),
3.79 (dd, J = 2.6, 9.7 Hz, 2H, NCHH), 2.95 (d, 4H, J = 4.6 Hz,
CH2Ph), 2.56 (s, 3H, CH3CN), 2.35 (s, 6H, CH3). 13C NMR (100
MHz, CDCl3): d 175.2, 168.5, 138.2, 136.2, 135.2, 132.8, 130.1,
130.0, 128.4, 126.8, 125.6, 125.1, 123.3, 60.0, 58.9, 41.0, 21.1, 2.9.
Anal. calcd for C42H40BF4N5Ni: C, 66.35; H, 5.30; N, 9.21. Found:
C, 66.53; H, 5.51; N, 9.21%.
2,6-Bis((S)-4-benzyl-1-cyclohexyl-4,5-dihydro-1H-imidazol-2-
yl)phenylchloronickel(II) (2d). Orange solid in 48% isolated yield.
◦
mp: 210–211 C. [a]2D0 +191 (c 0.112 in CH2Cl2). IR (KBr):
n
max/cm-1 3057, 3023, 2930, 2853, 1600, 1568, 1527, 1434, 1326,
1
1259, 1188, 1165, 1088, 1054, 996, 891, 789, 742, 720, 700. H
NMR (400 MHz, CDCl3): d 7.38 (d, J = 7.2 Hz, 4H, Ph), 7.27–
7.16 (m, 8H, Ph and central Ar (3,5)), 6.99 (t, J = 7.7 Hz, 1H,
central Ar (4)), 4.21–4.15 (m, 2H, NCH), 3.98–3.91 (m, 2H, N-
Cy), 3.56 (app t, J = 10.0 Hz, 2H, NCHH), 3.50 (dd, J = 3.2, 13.1
Hz, 2H, CHHPh), 3.45 (dd, J = 3.2, 9.9 Hz, 2H, NCHH), 2.65
(dd, J = 9.4, 13.1 Hz, 2H, CHHPh), 1.85–1.67 (m, 10H, Cy), 1.44–
1.25 (m, 8H, Cy), 1.13–1.08 (m, 2H, Cy). 13C NMR (100 MHz,
CDCl3): d 179.1, 168.4, 138.5, 133.8, 129.9, 128.2, 126.1, 123.0,
122.6, 60.2, 54.6, 49.6, 41.0, 31.8, 30.6, 25.6, 25.4, 25.2. Anal. calcd
for C38H45ClN4Ni·2.5CH2Cl2: C, 56.28; H, 5.83; N, 6.48. Found:
C, 56.03; H, 5.75; N, 6.46%.
General procedure for the asymmetric Michael addition of ethyl
2-cyanopropionate to methyl vinyl ketone
2,6-Bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)-
phenylchloronickel(II) (2e). Orange solid in 76% isolated yield.
Under a nitrogen atmosphere, the catalyst (0.01 mmol, 5.0 mol%)
was dissolved in 2 mL of solvent. N-ethyldiisopropylamine
(0.02 mmol, 3.5 mL) was added, followed by methyl vinyl ketone
(0.3 mmol, 24 mL), and finally ethyl 2-cyanopropionate (0.2 mmol,
25.5 mL). The resulting solution mixture was stirred for the allotted
times and temperatures (Table 2). The solvent was removed, and
the residue was purified by flash column chromatography to give
the product 4 (ethyl ether/petroleum ether, 1 : 1). The enantiomeric
excess was determined by chiral-phase HPLC (Daicel Chiralpak
AD-H column).
◦
mp: 190–191 C. [a]2D0 +200 (c 0.096 in CH2Cl2). IR (KBr):
n
max/cm-1 3028, 2921, 1570, 1511, 1426, 1299, 1157, 821, 761,
697. 1H NMR (400 MHz, CDCl3): d 7.42 (d, J = 7.4 Hz, 4H, Ph),
7.33 (t, J = 7.6 Hz, 4H, Ph), 7.22 (t, J = 8.0 Hz, 2H, Ph, partially
overlapped with NAr), 7.20 (d, J = 8.2 Hz, 4H, NAr, partially
overlapped with Ph), 7.14 (d, J = 8.2 Hz, 4H, NAr), 6.60 (t, J =
7.6 Hz, 1H, central Ar (4)), 6.46 (d, J = 7.6 Hz, 2H, central Ar
(3,5)), 5.14 (dd, J = 3.5, 10.6 Hz, 2H, NCH), 4.42 (app t, J = 10.3
Hz, 2H, NCHH), 3.92 (dd, J = 3.5, 9.7 Hz, 2H, NCHH), 2.39 (s,
6H, CH3). 13C NMR (100 MHz, CDCl3): d 179.3, 168.1, 143.8,
137.6, 136.8, 132.7, 130.1, 128.5, 127.2, 126.7, 125.7, 124.7, 121.8,
64.2, 62.8, 21.1. Anal. calcd for C38H33ClN4Ni: C, 71.33; H, 5.20;
N, 8.76. Found: C, 70.99; H, 5.51; N, 8.45%.
Ethyl 2-cyano-2-methyl-5-oxohexanoate 45d
1
Colorless oil. H NMR (400 MHz, CDCl3): d 4.27 (q, J = 7.1
Hz, 2H, OCH2), 2.75–2.61 (m, 2H, CH2), 2.19 (s, 3H, COCH3),
2.02–2.24 (m, 2H, CH2), 1.62 (s, 3H, C(CN)CH3), 1.29 (t, J = 7.1
Hz, 3H, CH3).
General procedure for the synthesis of the cationic Ni(Phebim)
complexes 3a and 3c
Crystal structure determination and data collection
In a flask protected from light, Ni(Phebim)Cl (0.35 mmol) and
AgBF4 (136 mg, 0.7 mmol) were stirred in CH3CN/CH2Cl2 (20
mL, v/v 1 : 1) at room temperature for 12 h. After the solvent was
removed under reduced pressure, the residue redissolved in CH2Cl2
and filtered through Celite. The resulting solution was evaporated
to dryness and the residue washed with Et2O, yielding pure 3 as a
yellow solid.
Crystals of 2a and 2c were obtained by recrystallization from ethyl
acetate and those of 2b and 3c from CH2Cl2/n-hexane at ambient
temperature. The data of 2a–c were collected with Rigaku-
IV imaging plate area detector with graphite-monochromated
˚
Mo-Ka radiation (l = 0.71073 A) and those of 3c were col-
lected on a Oxford diffraction Gemini E diffractometer with
˚
graphite-monochromated Cu-Ka radiation (l = 1.54184 A) at
Cationic Ni(Phebim) complex 3a
ambient temperature. The diffraction data were corrected for
Lorentz and polarization factors. The structures were solved
by direct methods and expanded using Fourier techniques and
refined by full-matrix least-squares methods. The non-hydrogen
atoms were refined anisotropically, and the hydrogen atoms were
◦
45% isolated yield. mp: 188 C (dec.). [a]2D0 +306 (c 0.066 in
CH2Cl2). IR(KBr): nmax/cm-1 3031, 2925, 2866, 1575, 1537, 1512,
1430, 1297, 1158, 1107, 1039, 820, 764, 722, 670, 647, 580, 519.
1H NMR (400 MHz, CDCl3): d 7.22 (d, J = 8.1 Hz, 4H, NAr),
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9012–9019 | 9017
©