R. H. Grubbs and G. C. Vougioukalakis
N-(2,4,6-Trifluorophenyl)-N’-mesityloxalamide (16a): Compound 15a
(2.47 g, 10.0 mmol, 1.0 equiv) was suspended in 2,4,6-trimethylaniline
(2.53 mL, 18.0 mmol, 1.8 equiv) in a dry Schlenk tube under nitrogen.
The tube was sealed and the suspension was stirred at 1808C for 16 h.
Upon being cooled to room temperature, the reaction mixture solidified.
The orange-brown solid was washed with diethyl ether (45 mL) and
hexanes (25 mL), leaving 16a as a white solid (1.41 g, 4.2 mmol, 42%
yield). 1H NMR (300 MHz, CDCl3, 258C): d=9.07 (brs, 1H), 8.81 (brs,
1H), 6.90 (s, 2H), 6.79–6.74 (m, 2H), 2.29 (s, 3H), 2.18 ppm (s, 6H);
13C{1H} NMR (75 MHz, CDCl3, 258C; due to extensive fluorine coupling,
coupling constants are not given and resonances are reported as peaks):
d=159.91–159.62 (m), 158.74, 157.41, 156.55–156.25 (m), 137.94, 134.93,
129.58, 129.26, 101.44–100.71 (m), 21.17, 18.52 ppm; 19F{1H} NMR
(282 MHz, CDCl3, 258C): d=À108.18, À113.65 ppm; HRMS (FAB+):
m/z calcd for C17H16N2O2F3 [M+]: 337.1164; found: 337.1164.
to extensive fluorine coupling and the existence of two rotational iso-
mers, coupling constants are not given and resonances are reported as
peaks): d=297.57 (major), 293.43 (minor), 223.44, 222.80, 164.00–163.84
(m), 162.94–162.76 (m), 160.89–160.69 (m), 155.69–155.42 (m), 152.31–
152.21 (m), 152.02–151.86 (m), 151.21, 142.89–142.75 (m), 138.87, 138.24,
136.90–136.77 (m), 136.59, 135.09, 131.02–130.50 (m), 130.00, 129.18,
128.91, 128.53, 128.02–127.83 (m), 101.87–101.44 (m), 101.03–100.60 (m),
53.10–53.05 (m), 52.76, 52.22, 52.20, 32.15, 32.02, 31.96, 31.83, 29.26,
28.00, 27.92, 27.84, 26.39, 26.36, 21.07, 20.86, 19.68, 18.28 ppm; 31P{1H}
NMR (121 MHz, CD2Cl2, 258C) d=31.94 (s, minor), 27.33 ppm (s,
major); 19F{1H} NMR (282 MHz, CD2Cl2, 258C): d=À105.01 (d, major,
J
FF =18 Hz), À106.15 (brs, major), À108.25 (d, minor,
JFF =18 Hz),
À114.02 ppm (brs, minor); HRMS (FAB+): m/z calcd for
C43H56N2F3Cl2PRu [M+]: 860.2554; found: 860.2536.
[RuCl2(1-(2,4,6-trifluorophenyl)-3-mesityl-4,5-dihydroimidazol-2-yli-
À
dene)(=CH-o-iPrO Ph)] (9): In a glovebox, a vial was charged with
complex 8 (172 mg, 200 mmol, 1.0 equiv), toluene (4 mL), and o-isopro-
poxy-b-methylstyrene (175 mg, 4.0 mmol, 20.0 equiv). The dark red solu-
tion was stirred for 10 min and then left inside the capped vial without
stirring at room temperature. After 48 h the desired complex had precipi-
tated as dark green crystals. The supernatant brown liquid was decanted
off; the crystals were washed with pentanes (310 mL) and dried in
vacuo to afford complex 9 (109mg, 171 mmol, 85% yield). Crystals suita-
ble for X-ray crystallography were grown at room temperature by slow
diffusion of hexanes into a solution of 9 in benzene. 1H NMR (500 MHz,
CD2Cl2, 258C): d=16.10 (s, 1H), 7.56–7.53 (m, 2H), 7.12 (s, 2H), 6.94–
N-(2,4,6-Trifluorophenyl)-N’-mesityl-1,2-ethanediamine dihydrochloride
(17a): In a dry, high pressure tube containing 16a (1.68 g, 5.0 mmol,
1.0 equiv), BH3·THF (1m in THF) (25 mL, 25.0 mmol, 5.0 equiv) was
added under nitrogen. The tube was sealed and the solution was stirred
at 708C for 16 h. Once the reaction mixture had cooled to room tempera-
ture, the clear yellowish solution was slowly added to methanol (50 mL)
at 08C. Concentrated aqueous HCl solution (1.8 mL) was also slowly
added at 08C. When all bubbling ceased, the solvent was removed under
reduced pressure. The resulting solid was dissolved in methanol and the
solvent was again removed under reduced pressure. This was repeated
twice more to remove the remaining boron as B(OMe)3. The remaining
A
6.89(m, 4H), 5.00 (septet, 3J
(s, 3H), 2.30 (s, 6H), 1.36 ppm (d, 3J
ACHTREUNG
white solid was finally washed with diethyl ether (25 mL) to provide
the desired product as a white powder (1.53 g , 4.0 mmol, 80% yield).
1H NMR (300 MHz, [D6]DMSO, 258C): d=7.11–7.05 (m, 2H), 6.96 (s,
2H), 3.59–3.33 (m, 4H), 2.48 (s, 6H), 2.37 ppm (s, 3H); 13C{1H} NMR
(75 MHz, [D6]DMSO, 258C; due to extensive fluorine coupling, coupling
constants are not given and resonances are reported as peaks): d=
152.51–152.34 (m), 138.26, 131.82, 130.31, 124.95–124.60 (m), 116.97–
116.64 (m), 111.86–111.43 (m), 50.57, 41.32, 20.16, 17.57 ppm; 19F{1H}
NMR (300 MHz, [D6]DMSO, 258C): d=À123.19, À125.29ppm; HRMS
(FAB+): m/z calcd for C17H20N2F3 [M+]: 309.1579; found: 309.1587.
AHCTREUNG
(125 MHz, CD2Cl2, 258C; due to extensive fluorine coupling, coupling
constants are not given and resonances are reported as peaks): d=
292.19, 215.59, 164.56–164.32 (m), 163.31–163.14 (m), 163.31–163.14 (m),
162.43–162.32 (m), 161.27–161.10 (m), 152.45, 144.53, 139.46, 137.93,
137.50, 129.91, 129.85, 122.61, 122.51, 113.11, 101.45–101.04 (m), 75.50,
53.15, 51.84, 21.29, 21.16, 17.96 ppm; 19F{1H} NMR (282 MHz, CD2Cl2,
258C): d=À103.97, À106.17 ppm; HRMS (FAB+): m/z calcd for
C28H29N2OF3Cl2Ru [M+]: 638.0653; found: 638.0658.
N-(2,3,4,5,6-Pentafluorophenyl)-N’-mesityloxalamide (16b): Compound
15b (1.35 g, 6.0 mmol, 1.0 equiv) was added to a solution of 2,3,4,5,6-pen-
tafluoroaniline (2.42 g, 13.2 mmol, 2.2 equiv) in dry THF (60 mL) under
nitrogen. After stirring the reaction mixture at room temperature for 2 h,
the solvent was evaporated under reduced pressure. The remaining solid
was washed with hexanes (310 mL) and dried under high vacuum to
afford the desired compound as a white solid (2.12 g, 5.7 mmol, 95%
yield). 1H NMR (300 MHz, CDCl3, 258C): d=9.14 (brs, 1H), 8.68 (brs,
1H), 6.92 (s, 2H), 2.30 (s, 3H), 2.20 ppm (s, 6H); 13C{1H} NMR (75 MHz,
CDCl3, 258C; due to extensive fluorine coupling, coupling constants are
not given and resonances are reported as peaks): d=158.68, 157.12,
144.83–144.44 (m), 142.61–142.14 (m), 141.48–141.19 (m), 139.85–139.41
(m), 139.23–138.75 (m), 138.10, 136.55–136.06 (m), 134.80, 129.30, 129.12,
111.07–110.52 (m), 21,08, 18.34 ppm; 19F{1H} NMR (282 MHz, CDCl3,
1-(2,4,6-Trifluorophenyl)-3-mesityl-4,5-dihydroimidazolium
chloride
(18a): A suspension of 17a (1.53 g, 4.0 mmol, 1.0 equiv) in triethylortho-
formate (13.3 mL, 80.0 mmol, 20.0 equiv) was heated at 1358C for 30 min
under nitrogen. Upon cooling to room temperature, the solids were fil-
tered of and washed with diethyl ether (310 mL) to provide the desired
product as
a white solid (1.28 g ,
3.6 mmol, 90% yield). 1H NMR
(300 MHz, [D6]DMSO, 258C): d=9.59 (s, 1H), 7.64–7.58 (m, 2H), 7.07
(s, 2H), 4.58–4.64 (m, 4H), 2.30 (s, 6H), 2.26 ppm (s, 3H); 13C{1H} NMR
(75 MHz, [D6]DMSO, 258C; due to extensive fluorine coupling, coupling
constants are not given and resonances are reported as peaks): d=
162.15–161.19(m), 140.54, 135.78, 131.32, 130.17, 124.79–124.79(m),
111.93–111.39 (m), 103.15–102.37 (m), 52.20, 52.06, 21.24, 17.78 ppm;
19F{1H} NMR (282 MHz, [D6]DMSO, 258C): d=À105.45, À116.29ppm;
HRMS (FAB+): m/z calcd for C18H18N2F3 [M+]: 319.1422; found:
319.1421.
258C): d=À143.95 (d,
J
C
À161.85 ppm (t,
A
A
C17H13N2O2F5 [M+]: 372.0897; found: 372.0893.
À
N
N
N-(2,3,4,5,6-Pentafluorophenyl)-N’-mesityl-1,2-ethanediamine
dihydro-
and KHMDS (337 mg, 1.0 mmol, 2.0 equiv) were stirred in benzene
(10 mL) at room temperature for 30 min. Catalyst 2 (411 mg, 500 mmol,
1.0 equiv) was added as a solid in one portion, and the reaction flask was
taken out of the glove box and heated under a nitrogen atmosphere at
808C for 30 min. The solution was concentrated to 2 mL in vacuo and
poured onto a column packed with TSI Scientific silica gel. The complex
was eluted with hexanes/diethyl ether (2:1) as a red band. This was con-
centrated in vacuo, transferred in a glove box, dissolved in the minimum
amount of benzene and lyophilized to afford the desired complex as a
violet solid (345 mg, 401 mmol, 80% yield). Crystals suitable for X-ray
crystallography were grown at room temperature by slow diffusion of
hexanes into a solution of 8 in benzene. 1H NMR (500 MHz, CD2Cl2,
258C): d=19.48 (s, 1H-minor), 19.12 (s, 1H-major), 7.47–6.88 (m, 9H-
major, 9H-minor), 4.10–3.90 (m, 4H-major, 4H-minor), 2.62–1.00 ppm
(m, 42H-major, 42H-minor); 13C{1H} NMR (125 MHz, CD2Cl2, 258C; due
chloride (17b): This was synthesized analogously to 17a starting with 16b
(white powder, 60% isolated yield). 1H NMR (300 MHz, [D6]DMSO,
258C): d=6.95 (s, 2H), 3.76 (t, 3J
N
N
6 Hz, 2H), 2.44 (s, 6H), 2.20 ppm (s, 3H); 13C{1H} NMR (75 MHz,
[D6]DMSO, 258C; due to extensive fluorine coupling, coupling constants
are not given and resonances are reported as peaks): d=139.92–139.63
(m), 139.50–139.18 (m), 138.99, 136.89–136.01 (m), 134.25–133.88 (m),
132.60, 131.39, 130.99, 124.46–124.12 (m), 50.94, 41.81, 20.81, 18.39 ppm;
19F{1H} NMR (282 MHz, [D6]DMSO, 258C): d=À159.54 to À159.65 (m),
À165.66 to À165.81 (m), À174.82 to À174.92 ppm (m); HRMS (FAB+):
m/z calcd for C17H18N2F5 [M+]: 345.1390; found: 345.1396.
1-(2,3,4,5,6-Pentafluorophenyl)-3-mesityl-4,5-dihydroimidazolium
chlo-
ride (18b): A suspension of 17b (834 mg, 2.0 mmol, 1.0 equiv) in triethyl-
orthoformate (6.6 mL, 40.0 mmol, 20.0 equiv) was heated at 1358C for
7552
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 7545 – 7556