The Role of Symmetry in Ring-Closing Metathesis
FULL PAPER
AM300 and a Bruker AVANCE 400 operating at 300 and 400 MHz for
1H, respectively. The 1H and 13C NMR chemical shifts are referenced to
SiMe4 (d = 0 ppm) using the residual proton impurities of the deuterated
solvents as internal standards. 31P NMR spectra were referenced using
H3PO4 (d = 0 ppm) as an external standard. Spectra are reported as fol-
lows: chemical shift (ppm), multiplicity, coupling constant (Hz), and inte-
gration. Multiplicities are abbreviated as follows: singlet (s), doublet (d),
triplet (t), quartet (q), multiplet (m), and broad (br). Elemental analysis
was done on a with a PERKIN-Elmer 240-C analyzer. Compounds 17,
19[49], and 21[43], as well as ruthenium complexes 7a and 8a[14] were pre-
pared according to literature procedures.
140.2, 140.0, 139.2, 138.9, 138.4, 131.1, 130.2, 130.0, 129.3, 129.1, 129,
128.3, 128, 127.6, 127.5, 126.9, 123, 122.7, 122.3, 113.5, 75.3, 66.0, 62.0,
61.4, 56.1, 36.1, 35.5, 30.6, 30.2, 28.3, 27.5, 27.4, 27.0, 26.8, 22.4, 22.2, 22.0,
19.5, 19.0, 18.5, 14.0, 13.8, 12.1 ppm; elemental analysis calcd (%) for
C29H34Cl2N2ORu (598.57): C 58.19, H 5.73, N 4.68; found C 58.20, H
5.70, N 4.68.
AHCTUNGTERG[NNUN (meso)-1,3-Bis(2-isopropylphenyl)-4,5-dimethylimidazolin-2-ylidene]di-
chloro(2-isopropoxybenzylidene)ruthenium(II) (9b): Using the procedure
described for the preparation of 9a, the reaction of the imidazolinium
salt 13b (0.84 mmol, 312 mg), KHMDS (0.93 mmol, 184 mg) and [RuCl2-
AHCTUNGTRENN(GNU PCy3)(=CH-o-OiPrC6H4)] (0.45 mmol, 267 mg) in toluene (4 mL) afford-
ed the desired compound (9b, 0.30 mmol, 200 mg) in 68% yield as a
bright green crystalline solid (hexane and diethyl ether, 2:1 to 1:1).
1H NMR (400 MHz, CD2Cl2): d=16.40 (major isomer: s, Ru=CH-o-
OiPrC6H4), 16.13 (minor isomer: s, Ru=CH-o-OiPrC6H4), 8.76 (d), 7.63–
7.37 (m), 7.19 (t), 6.92–6.84 (m), 4.96 (m), 4.80 (m), 4.60 (m), 4.46 (m),
4.27 (m), 3.50 (m), 3.39–3.29 (m), 1.54–1.10 (overlapped peaks), 0.84 ppm
(d); 13C NMR (400 MHz, CD2Cl2): d=296.1, 295.2, 209.9, 152.9, 148.7,
148.4, 148.2, 144.2, 140.6, 139.0, 138.6, 138.0, 132.3, 131.6, 130.1, 129.9,
129.6, 129.1., 128.7, 128.1, 127.9, 127.7, 122.8, 122.4, 122.1, 113.4, 75.1,
75.0, 66.5, 64.0, 63.3, 63.0, 28.9, 28.6, 28.5, 27.4, 25.9, 25.2, 25.0, 24.2, 24.1,
23.4, 23.2, 22.5, 22.1, 21.8, 14.1, 13.7, 12.7 ppm; elemental analysis calcd
(%) for C33H42Cl2N2ORu (654.67): C 60.54, H 6.47, N 4.28; found C
60.54, H 6.43, N 4.31.
ACHTUNGTRENNUNG[(meso)-1,3-Bis(2-isopropylphenyl)-4,5-dimethylimidazolin-2-ylidene]di-
chloro(benzylidene)(tricyclohexylphosphine)ruthenium(II) (7b): In a glo-
vebox, a 50 mL Schlenk tube was charged with the imidazolinium salt
13b (0.77 mmol, 287 mg), potassium hexamethyldisilazide (KHMDS,
0.8 mmol, 159 mg), and toluene (6.9 mL). The reaction mixture was
stirred at room temperature for 30 min. Then [RuACTHUNGTRENNG(U PCy3)2ACHTUNGTNER(NUGN =CHPh)Cl2]
(0.65 mmol, 538 mg) was added, and the reaction mixture was stirred for
1.5 h at room temperature. After this time, the reaction mixture was con-
centrated and purified by flash column silica gel chromatography (diethyl
ether and pentane, 1:9 to 1:1) to afford 7b as a green-brown powder
1
(0.46 mmol, 405 mg, 60%). H NMR (400 MHz, CD2Cl2): d=19.2 (minor
isomer: s, Ru=CHPh), 19.0 (major isomer: s, Ru=CHPh), 8.56 (d), 8.40
(d) 7.63–7.27 (m), 7.22–6.91 (m), 6.85–6.69 (m), 6.39 (brs), 4.70–4.37 (m),
4.23–4.03 (m), 3.67 (brs), 3.55 (s), 2.0–0.71 ppm (several peaks);
AHCTUNGTERG[NNUN (4S,5S)-1,3-Bis(2-methylphenyl)-4,5-dimethylimidazolin-2-ylidene]di-
13C NMR (100 MHz, C6D6): d=300.6 (brs, Ru=CHPh), 219.6 (d, J
ACHTUNGTRENNUNG
chloro(2-isopropoxybenzylidene)ruthenium(II) (10a): The ruthenium
complex 8a[14] (0.15 mmol, 125 mg) and CuCl (0.17 mmol, 17 mg) were
added to a 50 mL round bottom flask in a glovebox and were dissolved
77.7 Hz, iNCN), 217.6 (d, JACHTGNUTRENNUNG
148.9, 148.7, 148.3, 148.2, 147, 138.8, 138.6, 138.2, 137.4, 137.1, 136.8,
136.2, 134.7, 134.2, 133.9, 133.7, 133.2, 131.1, 130.1, 129.8, 129.5, 129.2,
127.5, 127.4, 127.3, 127.2, 127, 126.8, 126.6, 126.3, 126.2, 65.9, 64.3, 63.4,
63.1, 62.8, 33.6, 33.5, 33.3, 33.2, 29.4, 29.2, 28.5, 28.4, 27.1, 27, 26.2, 25.9,
25.5, 24.9, 24.5, 14.2, 14, 13.8, 13.2, 12.9 ppm. 31P NMR (161.97 MHz,
C6D6): d=23.8 (minor isomer) 22.6 ppm (major isomer); elemental anal-
ysis calcd (%) for C48H69Cl2N2PRu (877.02): C 65.74, H 7.93, N 3.19;
found C 65.70, H 7.96, N 3.20.
in dichloromethane (6 mL).
A
solution of 2-isopropoxystyrene
(0.15 mmol, 25 mg) in CH2Cl2 ( 4 mL) was then added, and the resulting
solution was stirred at 408C for 1 h. After cooling to room temperature,
the solvent was removed in vacuo and the crude catalyst was purified by
column chromatography (pentane and CH2Cl2, 1:1) to afford 10a as a
green powder (0.11 mmol, 64 mg, 70%). 1H NMR (300 MHz, CD2Cl2):
d=16.57 (brs, Ru=CH-o-OiPrC6H4), 16.42 (brs, Ru=CH-o-OiPrC6H4),
8.47 (brs), 7.57–7.39 (m), 6.91 (m), 4.91 (m), 4.20 (m), 4.00 (m), 2.49 (m),
1.90–1.71 (m), 1.35–1.26 ppm (m); 13C NMR (75 MHz, CD2Cl2): d=
296.7, 295.6, 210.0, 152.6, 144.6, 141.4, 140.0, 139.1, 138.9, 138.2, 133.8,
132.9, 131.7, 131.6, 131.1, 130.3, 129.9, 129.2, 128.0, 127.2, 127.0, 122.7,
122.3, 113.3, 77.0, 75.2, 71.2, 66.9, 65.5, 64.7, 32.1, 31.7, 31.2, 29.1, 30.0,
29.7, 27.7, 27.5, 26.4, 25.6, 22.8, 19.9, 19.4, 18.8, 18.2 ppm; elemental anal-
ysis calcd (%) for C29H34Cl2N2ORu (598.57): C 58.19, H 5.73, N 4.68;
found C 58.20, H 5.70, N 4.68.
ACHTUNGTRENNUNG[(4S,5S)-1,3-Bis(2-isopropylphenyl)-4,5-dimethylimidazolin-2-ylidene]di-
chloro(benzylidene)(tricyclohexylphosphine)ruthenium(II) (8b): Using
the procedure described for the preparation of 7b, the imidazolinium salt
14b (0.90 mmol, 337 mg), KHMDS (0.94 mmol, 188 mg), and [Ru
ACHTUNGTRNE(NUNG PCy3)2-
ACHTUNGTRENNUNG
fording 8b (0.58 mmol, 510 mg) in 65% yield as a brown powder (diethyl
ether and pentane, 1:9 to 1:1). 1H NMR (400 MHz, CD2Cl2): d=19.2
(major isomer: s, Ru=CHPh), 19.1 (minor isomer: s, Ru=CHPh), 8.48
(d), 7.50–7.24 (m), 7.11–7.01 (m), 6.93 (brs), 6.82 (brt), 3.87 (m), 3.73
(m), 3.58 (m), 3.36 (brs), 1.84 (brm), 1.63–0.80 ppm (several peaks).
AHCTUNGTRENGN[UN (4S,5S)-1,3-Bis(2-isopropylphenyl)-4,5-dimethyl-imidazolin-2-ylidene]di-
chloro(2-isopropoxybenzylidene)ruthenium(II) (10b): Using the proce-
dure reported for the synthesis of 10a, the ruthenium complex 8b
(0.14 mmol, 120 mg), CuCl (0.15 mmol, 15 mg) and 2-isopropoxystyrene
(0.14 mmol, 23 mg) were reacted in dichloromethane (10 mL) to give 10b
(0.12 mmol, 79 mg, 88%) as a green powder (hexane and CH2Cl2, 1:1).
1H NMR (300 MHz, CD2Cl2): d=16.36 (s, Ru=CH-o-OiPrC6H4), 16.31 (s,
Ru=CH-o-OiPrC6H4), 8.56 (d), 7.61–7.36 (m), 6.88 (m), 4.91 (m),
4.24(m), 3.95 (m), 3.46 (m), 3.22 (m), 1.45–1.32 (m), 1.27 (m), 1.06 (m),
0.88 ppm (brm); 13C NMR (75 MHz, CD2Cl2): d=296.3, 295.6, 212.2,
209.9, 152.7, 149.9, 149.3, 149.1, 148.9, 144.6, 144.4, 140.4, 138.6, 137.1,
136.3, 134.2, 133.4, 132.9, 130.4, 129.8, 129.7, 129.6, 128.7, 127.8, 127.7,
127.5, 126.4, 127.2, 127.0, 126.6, 122.8, 122.3, 122.1, 113.3, 75.2, 75.1, 71.2,
68.4, 67.1, 66.2, 30.4, 30.1, 29.8, 29.1, 28.6, 28.3, 28.0, 27.5, 26.3, 26.0, 25.6,
24.6, 24.2, 23.7, 23.0, 22.2, 22.0, 19.9 ppm; elemental analysis calcd (%)
for C33H42Cl2N2ORu (654.67): C 60.54, H 6.47, N 4.28; found C 60.54, H
6.43, N 4.31.
13C NMR (100 MHz, C6D6): d=297.1 (s, Ru=CHPh), 218.9 (d, J
ACTHNUTRGNE(NUG P,C)=
76.8 Hz, iNCN), 152, 149.2, 147.6, 137.5, 136.2, 135.8, 133.9, 132.5, 130.2,
127, 126.1, 68.2, 67.8, 33.5, 33.4, 30.5, 28.5, 27.8, 27.1, 26, 25.9, 24.7, 24.3,
20, 19.8 ppm; 31P NMR (161.97 MHz, C6D6): d=24.9 (major isomer),
22.3 ppm (minor isomer); elemental analysis calcd (%) for
C48H69Cl2N2PRu (877.02): C 65.74, H 7.93, N 3.19; found C 65.72, H 7.90,
N 3.18.
ACHTUNGTRENNUNG[(meso)-1,3-Bis(2-methylphenyl)-4,5-dimethylimidazolin-2-ylidene]di-
chloro(2-isopropoxybenzylidene)ruthenium(II) (9a): In a glovebox, the
imidazolinium salt 13a[14] (0.47 mmol, 147 mg) and toluene (2 mL) were
placed in
103 mg) was then added. The resulting solution was stirred at room tem-
perature for ten minutes. [RuCl2A(PCy3)(=CH-o-OiPrC6H4)] (0.25 mmol,
a 50 mL Schlenk tube and stirred. KHMDS (0.51 mmol,
CTHUNGTRENNUNG
147 mg) was then added, and the mixture was stirred for 2 h at 708C.
After cooling to room temperature, the mixture was purified by column
chromatography on TSI silica gel (hexane and diethyl ether, 2:1 to1:1) to
give 9a (0.15 mmol, 88 mg, 60%) as a green crystalline solid. 1H NMR
(400 MHz, CD2Cl2): d=16.34 (major isomer: s, Ru=CH-o-OiPrC6H4),
16.26 (minor isomer: s, Ru=CH-o-OiPrC6H4), 8.59 (brd), 7.71–7.13 (m),
7.04 (brm), 6.92–6.68 (m), 4.96 (m), 4.73 (m), 4.53 (m), 4.32 (m), 4.07
(brs), 2.65 (d), 2.51 (d), 2.38 (d), 1.57–1.29 (m), 1.27–1.24 (m), 1.20–
1.12 ppm (m); 13C NMR (100 MHz, CD2Cl2): d=297.1 (minor isomer),
295.5 (major isomer), 212.9, 209.3, 153.0, 152.7, 144.8, 144.5, 141.7, 140.5,
Acknowledgements
The authors thank Francesco Funicello for the helpful discussion and
Patrizia Oliva for the technical assistance. LC gratefully acknowledges
the EC for funding this work through the European Communityꢄs Sev-
Chem. Eur. J. 2011, 17, 8618 – 8629
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
8627