Organometallics
Article
separatory funnel were added triphenylphosphine (197.0 mg, 0.792
mmol), [Ir(cod)Cl]2 (126.3 mg, 0.188 mmol), and NaBArF4 (500.0 mg,
0.564 mmol). CH2Cl2 (15 mL) and water (15 mL) were added, and the
funnel was shaken for 15 min. Diethyl ether was added until the layers
became fully separated. The organic layer was washed three times with
water and once with brine and dried over sodium sulfate. The solution
volume was reduced under vacuum, and the product was precipitated out
of solution by the addition of hexanes. The red-pink solid was dried
under vacuum. Yield: 412.0 mg (0.649 mmol, 65% yield).
(0.0056 mmol, 5 mol % with respect to quinaldine). The flask was
rapidly evacuated by vacuum and back-filled with H2 three times. The
flask was kept under ambient hydrogen pressure during the reaction.
Dry solvent (sparged with N2; 3 mL for each solvent screened) was
added to the flask, and the solution was stirred at room temperature
for 18 h. The solvent was removed in vacuo, and the resulting mixture
was redissolved in CD2Cl2. Conversion was assessed by comparative
integration of the product and starting material peaks to the internal
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standard in the H NMR spectrum. The spectra of pure quinaldine
and 1,2,3,4-tetrahydroquinaldine from commercially obtained samples
were used as peak references in identifying the products.
1H NMR (501 MHz, CD2Cl2): δ 7.73 (s, 8H, BAr4F), 7.56 (s, 4H,
BAr4F), 7.42 (m, 6H, PPh3), 7.35 (m, 12H, PPh3), 7.28 (m, 12H, PPh3),
4.19 (s, 4H, cod CH), 2.30 (m, 4H, cod CH2), 1.96 (m, 4H, cod CH2).
31P{1H} NMR (122 MHz, CD2Cl2): δ 17.71. 13C{1H} NMR (126 MHz,
Optimized Procedure for the Reduction of Substituted
Benzaldehydes. In a flame-dried 15 mL Schlenk tube under nitrogen
were added a stir bar, the substituted benzaldehyde (0.338 mmol), a
stock solution of toluene (dried, sparged with N2; 3 mL) that contained
trimethoxybenzene (10.0 mg, internal 1H NMR standard), and 3a
(0.0056 mmol, 5 mol % with respect to quinaldine). The flask was
rapidly evacuated by vacuum and back-filled with H2 three times. The
flask was kept under ambient hydrogen pressure during the reaction. The
solution was stirred at 80 °C for 24/48 h with aliquots taken at
designated time points. The solvent from the aliquots was removed in
vacuo. The yield was determined by comparative integration of the
CD2Cl2): δ 162.30 (q, J = 50.1 Hz), 135.35, 134.78 (J = 5.4 Hz), 131.90,
130.60−129.18 (m), 128.40 (s), 126.23, 118.03, 87.56 (t, J = 5.5 Hz),
31.59.
(η4-1,5-Cyclooctadiene)bis(triphenylphosphine)iridium Bis-
(trifluoromethanesulfonyl)imide. This known compound was
prepared using an alternative procedure.17 In a separatory funnel
were added triphenylphosphine (306.0 mg, 1.17 mmol), [Ir(cod)Cl]2
(196.0 mg, 0.292 mmol), and LiNTf2 (250.0 mg, 0.870 mmol).
CH2Cl2 (20 mL) and water (20 mL) were added, and the funnel was
shaken for 15 min. The organic layer was washed three times with
water and once with brine and dried over sodium sulfate. The solution
volume was reduced under vacuum, and the product was precipitated
out of solution by the addition of hexanes. The red-pink solid was
dried under vacuum. Yield: 313.9 mg (0.284 mmol, 48% yield). The
spectra of the product were identical with those previously reported.4
(η4-1,5-Cyclooctadiene)bis(diphenylcyclohexylphosphine)-
iridium Hexafluorophosphate. In a separatory funnel were added
diphenylcyclohexylphosphine (200.0 mg, 0.749 mmol), [Ir(cod)Cl]2
(100.0 mg, 0.149 mmol), and KPF6 (82 mg, 0.446 mmol). CH2Cl2
(15 mL) and water (15 mL) were added, and the funnel was shaken
for 15 min. Diethyl ether was added until the layers became fully
separated. The organic layer was washed three times with water and once
with brine and dried over sodium sulfate. The solution volume was
reduced under vacuum, and the product was precipitated out of solution
by the addition of hexanes. The red solid was dried under vacuum. Yield:
109.8 mg (0.161 mmol, 54% yield).
1
product and starting material peaks to the internal standard in the H
NMR spectrum. Spectra of pure starting material and alcohol products
from commercially obtained samples were used as peak references in
identifying the products.
Optimized Procedure for the Reductive Alkylation of
Quinaldine with Benzaldehydes. In a flame-dried 15 mL Schlenk
tube under nitrogen were added a stir bar, the substituted
benzaldehyde (0.338 mmol), a stock solution of toluene (dried,
sparged with N2; 3 mL) that contained quinaldine (15 μL, 0.112
mmol) and trimethoxybenzene (10.0 mg, internal 1H NMR standard),
and 3a (0.0056 mmol, 5 mol % with respect to quinaldine). The flask
was rapidly evacuated by vacuum and back-filled with H2 three times.
The flask was kept under ambient hydrogen pressure during the
reaction. The solution was stirred at 80 °C for 18 h. The solvent
was removed in vacuo, and the mixture was redissolved in CD2Cl2.
The yield was determined by comparative integration of the
product and starting material peaks to the internal standard in the
1H NMR spectrum. Isolated yields of the N-alkylated products
1H NMR (400 MHz, CD2Cl2): δ 7.47 (t, J = 7.1 Hz, 4H, PPh), 7.35
(m, 8H, PPh), 7.11 (t, J = 8.5 Hz, 8H, PPh), 4.29 (s, 4H, cod CH),
2.12 (m, 4H, cod CH2), 0.90−1.93 (m, 14H, PCy, cod CH2).
(7,8-Benzoquinolinato)hydrido(aqua)bis(tricyclohexylphos-
phine)iridium(III) Salts. Ir(PCy3)2H5 (125.0 mg, 0.1651 mmol) and
benzoquinoline (31.0 mg, 0.173 mmol) were added in a three-neck
round-bottom flask with an attached reflux condenser. The system was
evacuated and purged with dry nitrogen three times. Dry toluene (20.0
mL) was added via syringe. The solution was stirred under a flow of
nitrogen at reflux (110 °C) for 18 h. The solvent was removed in vacuo,
and the resulting orange solid was extracted using toluene (5 mL) and
precipitated by the addition of pentane (20 mL). The precipitating
solution was cooled to 0 °C, and the solid was collected by filtration.
This solid was then added to a solution containing 1.2 equiv of HX (where
could not reliably be separated from the crude mixtures using
standard column chromatography. The identity of the product was
supported by comparison of the 1H NMR to independently
synthesized samples (see the Supporting Information) and GC/MS
of the crude reaction mixture.
ASSOCIATED CONTENT
* Supporting Information
■
S
Text, tables, and figures giving further details about catalysis
and the characterization data of the products from reductive
alkylation reactions. This material is available free of charge via
X = PF6, (Et2O)2, BArF ) in wet CH2Cl2 (20 mL) under nitrogen, and
4
AUTHOR INFORMATION
Corresponding Author
the mixture was stirred for 2 h. The solvent was reduced in vacuo, and the
product was precipitated out by addition of pentane. A similar species with
a functionalized benzoquinoline group is known in the literature, isolated
by a variation of this procedure.18 The 1H NMR spectrum of the cation is
in close agreement with that of this similar complex. Ir(PCy3)2H5 was
prepared according to an established procedure.19
■
Present Addresses
†Department of Chemistry, University of Michigan.
‡Department of Chemistry, Massachusetts Institute of Technology.
§Department of Chemistry, Colorado State University.
1
3e, PF6 Salt. H NMR (300 MHz, CD2Cl2): δ 7.18−8.35 (m, 8H,
bq), 2.56 (s, 2H, H2O), 0.70−2.20 (m, 60H, PCy3), −15.67 (t, 1H,
2JH−P =14.66 Hz, Ir−H).
Notes
1
3f, BArF Salt. H NMR (300 MHz, CD2Cl2): δ 7.27−8.99 (m,
4
The authors declare no competing financial interest.
20H, bq, BArF ), 2.74 (s, 2H, H2O), 0.51−2.41 (m, 60H, PCy3),
−17.72 (m, 1H, Ir−H).
4
ACKNOWLEDGMENTS
■
Optimized Procedure for Quinaldine Reduction Screening
using Variants of 3. In a flame-dried 15 mL Schlenk tube under
nitrogen were added a stir bar, quinaldine (15 μL, 0.112 mmol),
trimethoxybenzene (10.0 mg, internal 1H NMR standard), and 3
This research was primarily supported by the U.S. Department
of Energy (DOE), Office of Science, Basic Energy Sciences
(BES), under catalysis award DE-FG02-84ER13297 (M.G.M.,
E
dx.doi.org/10.1021/om400267n | Organometallics XXXX, XXX, XXX−XXX