Single-Component Catalyst/Initiators
A R T I C L E S
Synthesis of 2 using Method B. In an inert atmosphere, 1,3-bis-
(2,4,6-trimethylphenyl)imidazolinium chloride (250 mg, 0.729 mmol)
was suspended in THF (7 mL). Potassium hydride (38 mg, 0.95 mmol)
was suspended in THF (2 mL) and added to the imidazolinium chloride
suspension. Methanol (27 µL, 0.67 mmol) was added to the resulting
suspension, and the mixture was stirred for 1 h. The mixture was then
filtered to remove residual salts, and the solvent removed under vacuum
to give 107 mg (47.2%) of the pure product as a white solid.
added via microsyringe to a solution of SIMes (200 mg, 0.653 mmol)
in dry THF (4 mL) in a 25 mL Schlenk flask. The resulting clear,
yellow solution was stirred at room temperature for 20 min and then
concentrated under vacuum. The resulting yellow solid was washed
with pentane and dried under vacuum to yield 146 mg (52.5%) of the
product as a pale yellow solid. 1H NMR (C6D6, 400 MHz): δ 2.15 (s,
6H), 2.49 (br s, 12H), 3.03 (m, 2H), 3.06 (s, 3H), 3.08 (m, 2H), 3.12
(m, 4H), 3.16 (m, 2H), 3.66 (m, 2H), 5.58 (s, 1H), 6.83 (s, 4H). 13C
NMR (C6D6, 400 MHz): δ 19.76, 21.32, 49.55, 58.97, 66.96, 70.93,
71.95, 72.54, 104.55, 130.12, 135.83, 138.98, 139.50.
X-ray Crystal Structure of SIMes(H)(OMe) (2). Full details are
contained in the Supporting Information. X-ray quality crystals of
SImMesHOMe were grown by cooling a saturated pentane solution of
2. A colorless rhombic crystal of C22H30N2O having approximate
dimensions of 0.30 × 0.21 × 0.17 mm was mounted on a quartz fiber
using Paratone N hydrocarbon oil. All measurements were made on a
Bruker-Siemens SMART CCD area detector with monochromatic
radiation of wavelength 0.71073 Å.
Synthesis of [SIMes(H)O]2(CH2CH2) (7). In an inert atmosphere,
1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride (230 mg, 0.671
mmol) was suspended in THF (5 mL). Potassium hydride (40 mg, 1.0
mmol) was suspended in THF (1 mL) and added to the imidazolinium
chloride suspension. Ethylene glycol (21 mg, 0.34 mmol) was added
to the combined suspension, and the mixture stirred for 1 h. The mixture
was then filtered via syringe filter, and the solvent removed under
vacuum to give the crude product as a yellow solid. The product was
purified by washing with a small amount of pentane (0.5 mL) to yield
Synthesis of SIMes(H)(OEt) (3). In a drybox under N2, a suspension
of KH (68 mg, 1.7 mmol) in dry THF (5 mL) was added to a stirred
suspension of 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride (386
mg, 1.13 mmol) in dry THF (10 mL) in a 20 mL vial. Ethanol (69 µL,
1.2 mmol) was added to the resulting cloudy white suspension via
microsyringe. The mixture was stirred at room temperature for 40 min
and then filtered to remove residual salts. The resulting clear, colorless
solution was concentrated under vacuum to yield 325 mg (81.9%) of
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44 mg (20%) of the pure product as a colorless crystalline solid. H
NMR (C6D6, 400 MHz): δ 2.18 (s, 12H), 2.34 (s, 24H), 2.72 (s, 4H),
3.03 (dd, 4H), 3.56 (dd, 4H), 5.22 (s, 2H), 6.78 (s, 8H). 13C NMR
(C6D6, 400 MHz): δ 19.64, 21.36, 49.47, 66.68, 104.25, 130.05, 135.55,
139.37.
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the product as a colorless sticky solid. H NMR (C6D6, 400 MHz): δ
Synthesis of [SIMes(H)OCH2]3CCH3 (8). In an inert atmosphere,
1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride (289 mg, 0.842
mmol) was suspended in THF (5 mL). Potassium hydride (51 mg, 1.3
mmol) was suspended in THF (1 mL) and added to the imidazolinium
chloride suspension. 2-(Hydroxymethyl)-2-methylpropane-1,3-diol (32
mg, 0.27 mmol) was added to the combined suspension, and the mixture
stirred 1 h. The mixture was then filtered via syringe filter, and the
solvent removed under vacuum to give the product as a white solid
(75 mg, 27%). 1H NMR (C6D6): δ 2.7 (s, 18H), 2.31 (s, 36H), 2.46 (s,
6H), 3.02 (dd, 6H), 3.27 (s, 3H), 3.52 (dd, 6H), 5.13 (s, 3H), 6.81 (s,
12H). 13C NMR (C6D6, 400 MHz): δ 18.61, 19.66, 21.47, 41.42, 49.53,
68.15, 71.70, 104.21, 129.92, 135.34, 139.71.
0.72 (t, 6.8 Hz, 2H), 2.15 (s, 6H), 2.51 (br s, 12H), 2.92 (q, 6.8 Hz,
2H), 3.14 (m, 2H), 3.67 (m, 2H), 5.52 (s, 1H), 6.85 (s, 4H). 13C NMR
(C6D6, 400 MHz): δ 15.94, 19.40, 20.94, 49.19, 62.38, 103.52, 129.73,
135.45, 138.64, 139.27.
Synthesis of 3 using Method C. N,N′-(2,4,6-Trimethylphenyl)-
ethylenediamine (0.31 g, 1.0 mmol) was dissolved in 3 mL of dry
triethylorthoformate. A 1 M solution of hydrogen chloride in diethyl
ether (1.0 mL, 1.0 mmol) was added by syringe. The suspension was
heated to 200 °C for 2 h. After cooling to room temperature, potassium
hydride (0.05 g, 1.0 mmol) was added and the suspension was stirred
for 30 min before being filtered and concentrated under vacuum to
yield 3 as an orange solid (0.16 g, 0.45 mmol, 45%).
Reaction of 2 with CDCl3. In an NMR tube, SIMes(H)(OMe) (41
mg, 0.134 mmol) was dissolved in dry benzene and CDCl3 (0.107 mL,
1.34 mmol) was injected via syringe. The 1H NMR spectrum was
recorded after 10 min. Formation of 1,3-dimesityl-2-deutero-2-trichlo-
romethylimidazolidine43 and methanol was observed in quantitative
yield. At longer times an increase in the chloroform peak was also
observed, indicative of a slower proton exchange between the MeOH
and CDCl3.
Synthesis of SIMes(H)(OiPr) (4). In a 25 mL Schlenk flask
equipped with a stir bar, 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-
ylidene (50 mg, 0.163 mmol) was dissolved in 5 mL of dry THF, and
isopropyl alcohol (0.062 mL, 0.817 mmol) was injected via syringe
under nitrogen. The mixture was stirred for 30 min, the volatiles were
evaporated, and the resulting white sticky solid was dried under vacuum
(50 mg, 86%). 1H NMR (400 MHz, C6D6): δ (d, 6.0 Hz, 6H), 2.15 (s,
6H), 2.43 (br s, 6H), 2.57 (br s, 6H), 2.99 (sept, 6.0 Hz, 1H), 3.15 (m,
2H), 3.67 (m, 2H), 5.54 (s, 1H), 6.85 (s, 4H). 13C NMR (C6D6, 400
MHz): δ 18.87 (br s), 20.01 (br s), 20.99, 23.08, 48.95, 69.32, 102.70,
129.47 (br s), 129.84 (br s), 135.41, 137.51 (br s), 139.94, 140.05 (br
s).
Reaction of 2 with CS2. In an NMR tube equipped with J-young
valve, SIMes(H)(OMe) 2 (10 mg, 0.03 mmol) was dissolved in 0.300
mL of dry benzene-d6 and carbon disulfide (0.018 mL, 0.30 mmol)
was injected via syringe under nitrogen. A red precipitate formed
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immediately, and methanol was observed by H NMR spectroscopy.
Synthesis of SIMes(H)(OPyr) (5). In a 25 mL Schlenk flask
equipped with a stir bar, 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-
ylidene (50 mg, 0.163 mmol) and 1-pyrenebutanol (45 mg, 0.163 mmol)
were dissolved in 0.5 mL of dry THF under nitrogen. The mixture
was stirred for 30 min, and the volatiles were evaporated. A yellow
solid formed, which was dried under vacuum (80 mg, 84%). 1H NMR
(400 MHz, C6D6): δ 1.27 (m, 2H), 1.50 (m, 2H), 2.07 (s, 6H), 2.50
(br s, 12H), 2.88 (t, 8.0 Hz, 2H), 2.98 (t, 6.0 Hz, 2H), 3.11 (m, 2H),
3.65 (m, 2H), 5.56 (s, 1H), 6.79 (s, 4H), 7.52 (d, 7.6 Hz, 1H), 7.75-
8.01 (m, 8H). 13C NMR (C6D6, 400 MHz): δ 19.41, 20.88, 28.25, 30.86,
33.14, 49.16, 66.81, 103.95, 123.92, 124.88, 125.04, 125.07, 125.63,
125.69, 125.94, 126.76, 127.26, 127.28, 127.90, 129.06, 129.73, 130.11,
131.47, 131.96, 135.49, 137.40, 139.21. Anal. Calcd for C41H44N2O:
C, 84.79; H, 7.64; N, 4.82. Found: C, 84.20; H, 7.74; N, 4.71.
The solvent was decanted, and the red solid was identified as SIMesCS2
by comparison of its 1H NMR spectrum to that reported in the
literature.31 1H NMR (300 MHz, CDCl3): δ 2.23 (s, 6H), 2.54 (s, 12H),
4.20 (s, 4H), 6.87 (s, 4H).
Typical Method for Polymerization of Lactide. A 25 mL Schlenk
flask, equipped with a stir bar, was charged with L-lactide (100 mg,
0.69 mmol) and dissolved in 1 mL of anhydrous THF. To this solution
was added SIMes(H)(OMe) (2.3 mg, 6.9 µmol). The reaction mixture
was stirred for 10 min, and the reaction was quenched with a drop of
acetic acid. The conversion was determined by 1H NMR spectroscopy.
The polymer was precipitated in methanol and dried to a constant weight
(89 mg, 89%, PDI ) 1.18, Mn ) 16500), and the degree of
polymerization was analyzed by 1H NMR spectroscopy (DP ) 89). 1H
NMR (acetone-d6): δ 1.46-1.56 (d, 3H, -CH3), 5.05-5.25 (q, H,
-CH-).
Synthesis of SIMes(H)(OCH2CH2OCH2CH2OMe) (6). In a drybox
under N2, di(ethylene glycol) methyl ether (78 µL, 0.65 mmol) was
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J. AM. CHEM. SOC. VOL. 127, NO. 25, 2005 9083