Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction

Article abstract of DOI:10.1021/acs.organomet.6b00239

We describe the preparation and catalytic reactions of new CCN pincer Rh and Ru complexes containing NCH-oxazoline hybrid ligands. Oxazolinyl-phenyl-imidazolium derivatives (3) were suitable ligand precursors for the CCN pincer scaffold. C-H bond activation of 3 with RhCl₃·3H₂O in the presence of NEt₃ yielded the desired CCN pincer Rh complexes 5 in 13-27% yields. The related CCN pincer Ru complexes 8-10 were synthesized in good yields by C-H bond activation of p-cymene Ru complexes 7 in the presence of NaOAc in DMF. The chiral complexes 8 and 9 had two diastereomers according to the coordination of CO and OAc ligands. The CCN Rh complexes showed catalytic activity for conjugate reduction of ethyl β-methylcinnamate with hydrosilane, with moderate enantioselectivity. The CCN Ru complexes were found to be active in the hydrogenation of aromatic ketones. In particular, hydrogenation of 9-acetylanthracene took place at not only the C=O bond but also the anthracene ring. The Ru complexes were also used as catalysts in the transfer hydrogenation of 9-acetylanthracene with 2-propanol; again, both the C=O bond and the anthracene ring were hydrogenated.

Full text of DOI:10.1021/acs.organomet.6b00239

Article
pubs.acs.org/Organometallics
Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and
Their Catalytic Activity for Hydrogenation and Conjugate Reduction
Jun-ichi Ito,* Kanae Sugino, Satoru Matsushima, Hiroki Sakaguchi, Hiroshi Iwata, Takahiro Ishihara,
and Hisao Nishiyama*
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Chikusaku, Nagoya 464-8603, Japan
S
* Supporting Information
ABSTRACT: We describe the preparation and catalytic
reactions of new CCN pincer Rh and Ru complexes containing
NCH-oxazoline hybrid ligands. Oxazolinyl-phenyl-imidazo-
lium derivatives (3) were suitable ligand precursors for the
CCN pincer scaffold. C−H bond activation of 3 with RhCl3·
3H2O in the presence of NEt3 yielded the desired CCN pincer
Rh complexes 5 in 13−27% yields. The related CCN pincer
Ru complexes 8−10 were synthesized in good yields by C−H bond activation of p-cymene Ru complexes 7 in the presence of
NaOAc in DMF. The chiral complexes 8 and 9 had two diastereomers according to the coordination of CO and OAc ligands.
The CCN Rh complexes showed catalytic activity for conjugate reduction of ethyl β-methylcinnamate with hydrosilane, with
moderate enantioselectivity. The CCN Ru complexes were found to be active in the hydrogenation of aromatic ketones. In
particular, hydrogenation of 9-acetylanthracene took place at not only the CO bond but also the anthracene ring. The Ru
complexes were also used as catalysts in the transfer hydrogenation of 9-acetylanthracene with 2-propanol; again, both the CO
bond and the anthracene ring were hydrogenated.
metal catalysis.5 Recently, NHCs have been used in a tridentate
INTRODUCTION
■
ligand system.6 In particular, CCC pincer complexes with
Chiral and achiral pincer complexes with a metal−carbon bond
serve as efficient and selective catalysts in various trans-
anionic biscarbene ligands (D and E) have been extensively
formations.1 We have previously studied chiral bis(oxazolinyl)-
studied as alternatives to PCP pincer complexes. Faller,
Crabtree, and co-workers synthesized the first CCC pincer
palladium complexes with ligand E by oxidative addition to the
Pd(0) complex.7 Similar Pd complexes were synthesized by C−
H bond activation.8 Hollis and co-workers found that
Zr(NMe2)4 was a suitable precursor for the CCC-Zr complex
containing ligand D, which was used in the preparation of the
first CCC-Ir, -Rh, and -Pt complexes.9 The CCC-Rh complex
was found to serve as a good catalyst in intramolecular
hydroamination and conjugate addition of arylboronic acids to
α,β-unsaturated ketones.9b,f Braunstein and co-workers re-
ported the direct preparation of CCC-Ir complexes by C−H
bond activation of bis(imidazolium) ligand precursors.10
Recently, Pd, Ru, Ni, and lanthanide complexes have been
extensively studied,11−14 and chiral pincer NHC ligands based
on a pyridine scaffold have also been developed for asymmetric
catalysis.15
phenyl (phebox, A) Rh complexes, which have been employed
as highly efficient and selective catalysts in asymmetric reactions
such as conjugate reduction, borylation, and alkynylation.2 In
this system, a C2 symmetric chiral environment and metalla-
cycles with a metal−carbon covalent bond induced high
performance in various reactions. The related phebox Ru
complexes were also found to act as catalysts for hydrogenation,
alkynylation, and cyclopropanation with high enantioselectiv-
ity.3 Recently, bis(imidazolinyl)s (B) and bis(imidazolidine)s
(C) have been developed as suitable chiral ligands for Rh, Pd,
and Pt catalysts.4
In this context, we designed a chiral CCN pincer ligand (F)
containing both NHC and oxazoline fragments connected by a
benzene scaffold.16 Here, we report the synthesis of NHC-
oxazoline ligand precursors and CCN pincer Rh and Ru
complexes. We also address the preliminary results for the
application to catalytic reactions, conjugate reduction of α,β-
N-Heterocyclic carbenes (NHCs), which are highly electron-
Received: March 23, 2016
donating, have been utilized as ancillary ligands for transition
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
unsaturated ester, and hydrogenation and transfer hydro-
genation of ketones.
the carbene carbon bonded to the Rh atom was observed as a
doublet peak at δ 180.9 ppm (JRhC = 51 Hz).
Further intramolecular C−H bond activation of 4 was
examined in an attempt to synthesize the CCN pincer complex.
However, thermal reaction of 4 in toluene-d8 at 100 °C under
an argon atmosphere, monitored using NMR spectroscopy,
resulted in no reaction even after 40 h. This result suggests that
oxidative addition of a C−H bond by the Rh(I) center is not a
suitable method in the NHC-oxazoline ligand framework.
Similarly, it was reported previously that type E ligands with an
Ir(I) center were reluctant to undergo C−H bond activation.10a
After further experiments, RhCl3·3H2O was found to be a
suitable metal source for cyclometalation of ligand precursor 3
(Scheme 3). When a mixture of 3a and RhCl3·3H2O in MeCN
RESULTS AND DISCUSSION
Preparation of the ligand precursors 3a−d is summarized in
Scheme 1. Two methyl groups on the benzene scaffold were
■
a
Scheme 1. Preparation of Ligand Precursors 3a−d
Scheme 3. Preparation of CCN Pincer Rh Complexes
a
(i) (CH2O)n, AcOH, HCl, 70°C, 3 days; (ii) SOCl2, reflux 2 h; (iii)
aminoalcohol, NEt3, CH2Cl2, rt; (iv) MeSO2Cl, rt; (v) 1-isopropyl-1H-
imidazole or 1-mesityl-1H-imidazole, 60°C.
introduced for regioselective metalation of CCN ligand
precursors.8,17 Reaction of 2,4-dimethylbenzoic acid with
formaldehyde in the presence of HCl yielded a mixture of
compounds chloromethylated at the 3 and 5 positions.18 After
crystallization of the crude mixture, 1 was isolated as a pure
product in 50% yield. Then, a carboxylic acid group of 1 was
converted to an oxazoline fragment according to the conven-
tional method. Treatment of 1 with thionyl chloride gave the
corresponding acid chloride, which was treated with (S)-
phenylglycinol followed by the addition of methanesulfonyl
chloride to afford the oxazoline derivative 2a in 82% yield.
Similarly, the use of (S)-valinol and 2-amino-2-methylpropan-1-
ol gave compounds 2b and 2c in 78 and 71% yields,
respectively. Finally, alkylation of the chloromethyl group of
2a−c with imidazole derivatives afforded oxazoline-imidazolium
compounds 3a−d in 73−94% yields. In the 1H NMR spectra of
3a−d, the characteristic signals of the imidazolium proton were
observed at δ 10.68−11.30 ppm.
was heated in the presence of NEt3, the CCN pincer Rh
complex 5a was detected. Purification by a silica gel column
afforded 5a in 22% yield. Similarly, 5c and 5d were obtained in
13 and 27% yield, respectively.
The 1H NMR spectrum of 5a revealed that both imidazolium
and the benzene rings of the ligand precursor 3a were
deprotonated, indicating the formation of Rh−C bonds. The
signals of the isopropyl group were observed as two doublet
peaks at δ 1.41 and 1.43 ppm, and the signals of the methylene
linker were AB quartet peaks. The 13C NMR spectrum of 5a
showed doublet signals at δ 162.2 (JRhC = 43 Hz) and 152.2
(JRhC = 33 Hz) ppm, which were assigned as the carbene
carbon of NHC and the ipso-carbon of the benzene ring
bonded to the Rh center, respectively. Similarly, the 13C NMR
spectrum of 5d showed doublet peaks for NHC carbon and the
ipso-carbon at 166.8 (JRhC = 44 Hz) and 150.3 (JRhC = 34 Hz),
respectively.
Next, preparation of CCN pincer Rh complexes by
cyclometalation of the ligand precursor 3 was examined
(Scheme 2). Reaction of 3b with [Rh(cod) (OH)]2 in THF
at room temperature afforded the corresponding NHC Rh(I)
complex 4 in 56% yield as a diastereoisomeric mixture.
1
Complex 4 was identified on the basis of H and 13C NMR
1
spectra. In the 13C NMR spectrum, the characteristic signal for
The H NMR spectrum of 5b measured in CDCl3 revealed
broad peaks at δ 0.8−1.6 ppm, probably attributable to the
isopropyl groups of oxazoline and NHC. This feature could
arise from the dimer structure, judging from the solid-state
structure determined by X-ray analysis (vide infra). In contrast,
the 1H NMR spectrum in CD3CN showed sharp signals for the
isopropyl groups of oxazoline and NHC. This change was likely
due to the formation of a mononuclear complex accompanied
by the coordination of CD3CN. In the 13C NMR spectrum
measured in CD3CN, the NHC carbon and the ipso-carbon
Scheme 2. Preparation of the NHC Rh Complex
B
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
were observed at δ 162.0 (JRhC = 43 Hz) and 163.4 (JRhC = 27
Hz) ppm, similar to those of 5a and 5d.
The molecular structures of 5b and 5d were confirmed by X-
ray analysis (Figures 1 and 2). Complex 5b had a dimer
which the Rh center had pseudo-octahedral geometry with a
meridional CCN ligand. The bulky NHC substituent likely
prevented the formation of a dimer structure. The equatorial
position was occupied by the H2O ligand to construct the
saturated complex. The Rh−Cipso bond length (1.975(2) Å) is
similar to the Rh−CNHC bond lengths (1.990(2) Å). Although
the C16−Rh1−N1 bond is almost linear (172.92(9)°), the
C1−Rh1−O2 bond angle (166.28(8)°) deviates more sig-
nificantly from linearity.
We next examined the preparation of CCN pincer Ru
complexes containing NHC-oxazoline ligands (Scheme 4).
Scheme 4. Preparation of CCN Pincer Ru Complexes
Figure 1. ORTEP diagram of 5b at the 50% probability level. Selected
bond lengths (Å) and angles (deg): Rh1−C1 1.979(4), Rh1−C16
1.975(4), Rh1−N1 2.097(3), Rh1−Cl1 2.3284(10), Rh1−Cl2
2.3716(10), Rh1−Cl4 2.6131(10), Rh2−C22 1.988(4), Rh2−C37
1.976(4), Rh2−N4 2.143(3), Rh2−Cl2 2.5275(9), Rh2−Cl3
2.3347(10), Rh2−Cl4 2.3760(10), C16−Rh1−N1 169.38(15), Cl1−
Rh1−Cl2 176.82(3), C1−Rh1−Cl4 164.57(11), C37−Rh2−N4
166.19(14), Cl3−Rh2−Cl4 177.90(4), C22−Rh2−Cl2 170.98(11),
Rh1−Cl2−Rh2 98.29(3), and Rh2−Cl4−Rh1 95.86(3).
Silver carbenes are known to be good precursors for
transmetalation with various transition metals.20 Reaction of
3a−c with Ag2O proceeded smoothly at room temperature to
give bis-NHC Ag complexes 6a−c in 89−92% yields. HRMS of
6a−c indicated that the two NHCs were coordinated to the Ag
center.
Figure 2. ORTEP diagram of 5d at the 50% probability level. Selected
bond lengths (Å) and angles (deg): Rh1−C1 1.975(2), Rh1−C16
1.990(2), Rh1−N1 2.0949(19), Rh1−O2 2.3071(19), Rh1−Cl1
2.3291(6), Rh1−Cl2 2.3317(7), C1−Rh1−C16 91.93(9), C1−Rh1−
N1 81.60(8), C16−Rh1−N1 172.92(9), C1−Rh1−O2 166.28(8), and
Cl1−Rh1−Cl2 176.73(2).
The transmetalation reaction of the NHC Ag complex 6a
with [RuCl2(p-cymene)]2 proceeded at 60 °C to give the
corresponding Ru complex 7a in 75% yield. Similarly, 7b and
structure in which two CCN Rh units were connected by
bridging Cl ligands. Each Rh center showed pseudo-octahedral
geometry with a meridionally coordinated NHC-oxazoline
ligand. The CCN ligand coordinated to Rh2 was distorted as a
result of steric repulsion between the oxazoline isopropyl group
and the NHC. The Rh−Cipso bond lengths (1.979(4) and
1.988(4) Å) were slightly longer than that of the NCN pincer
Rh complex (Rh−C = 1.921(7) Å).19 The Rh−CNHC bond
lengths (1.975(4) and 1.976(4) Å) were similar to those of the
Rh−Cipso bonds. Complex 5d was a monomeric structure in
1
7c were obtained in 49 and 62% yields, respectively. The H
NMR spectra of 7a−c revealed a 1:1 adduct of p-cymene and
NHC moieties. In the 13C NMR spectra of 7a−c, the signals for
the carbene carbon were observed at δ 173.6−173.7 ppm.
Further transformation by cyclometalation of 7 was
conducted to prepare desirable CCN pincer Ru complexes.
When a mixture of 7a and NaOAc was heated in DMF at 95
°C, cyclometalation took place to produce two Ru complexes,
C
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
8a and 9a. After separation by column chromatography, 8a and
9a were isolated in 67 and 13% yields, respectively. Cyclo-
metalation of 7b produced 8b and 9b in 50 and 27% yield,
respectively. The achiral complex 7c yielded the achiral
complex 10 in 58% yield. In this reaction, use of NaOAc and
DMF is necessary. NaOAc could be a source of the acetate
ligand, promoting acetate-assisted C−H bond activation of the
ligand precursor.21 At the same time, thermal decomposition of
DMF generates CO, which might be trapped by a Ru species.22
On the basis of 1H and 13C NMR and IR spectra, 8a,b, 9a,b,
and 10 were identified to be the carbonyl-acetate complexes
1
with the CCN ligand. In the H NMR spectrum of 8a, the
methyl groups on the central benzene ring appeared as two
singlet peaks, at δ 2.29 and 2.52 ppm, respectively. The signal
for the methyl group of the acetate ligand was found at a higher
field (δ 0.84 ppm), probably because of shielding by the phenyl
group on the oxazoline fragment. This feature suggests that the
acetate ligand occupies the same side of the oxazoline phenyl
1
Figure 3. ORTEP diagram of 8b at the 50% probability level. Selected
bond lengths (Å) and angles (deg): Ru1−C1 2.020(3), Ru1−C16
2.013(4), Ru1−C24 1.798(4), Ru1−N1 2.155(3), Ru1−O2 2.211(2),
Ru1−O3 2.277(2), O4−C24 1.167(5); C16−Ru1−N1 171.69(12),
C1−Ru1−O3 153.62(11), C1−Ru1−O2 96.30(10), C24−Ru1−C1
89.58(15), C24−Ru1−O2 173.34(14), O4−C24−Ru1 175.4(4), N2−
C16−Ru1 127.0(3), N3−C16−Ru1 129.7(3), and N2−C16−N3
103.2(3).
substituent. In the H NMR spectrum of 8b, the signal of the
acetate ligand appeared at δ 1.83 ppm, at lower field than the
acetate ligand of 8a. Two methyl groups were observed on the
central benzene, at δ 2.26 and 2.45 ppm, similar to those of 8a.
In the IR spectra, the absorption of the CO ligand was observed
at 1894 cm−1 (8a) and 1884 cm−1 (8b). These absorptions
were shifted to lower frequency compared with those of the
related phebox-Ru complexes (1905−1937 cm−1),3b−d indicat-
ing enhanced electron density in 8 compared with the phebox-
Ru complexes.
The spectral features of 9a were similar to those of 8a. The
1H NMR spectrum of 9a displayed signals for the methyl
groups on the benzene ring at δ 2.32 and 2.54 ppm. In contrast,
the signal for the acetate ligand was observed at lower field, δ
1.94 ppm, compared with that for 8a. This feature is considered
to be the result of a lack of shielding effect arising from the
benzene ring. IR spectra of 9 also showed a slightly higher
absorption for the CO ligand than in 8.
The molecular structures of 8b and 9b were determined by
X-ray analysis (Figures 3 and 4). Complexes 8b and 9b are six-
coordinated mononuclear structures with the CCN ligand
coordinated meridionally. In complex 8b, the Ru1−C1 bond
length (2.020(3) Å) is similar to those of the phebox-Ru
complexes (1.96−2.02 Å).3d The Ru−Ccarbene distance,
2.013(4) Å, is similar to the Ru1−C1 distance and is in the
same range as those of other Ru-NHC complexes.23 The C16−
Ru1−N1 bond angle is 171.69(12)°, which is close to that in
the Rh complex 5b (169.38(15)°). The coordination site of the
acetate ligand is on the same side of the isopropyl group in the
oxazoline fragment. The CO ligand is coordinated vertical to
the plane of the CNN ligand framework. In 9b, the Ru1−C1
(2.010(3) Å) and Ru1−C16 (2.039(3) Å) bond lengths are
similar to those of 8b, but the coordination sites of acetate and
CO ligands are on the opposite side.
Figure 4. ORTEP diagram of 9b at the 50% probability level. Selected
bond lengths (Å) and angles (deg): Ru1−C1 2.010(3), Ru1−C16
2.039(3), Ru1−C24 1.784(3), Ru1−N1 2.121(2), Ru1−O2
2.1956(19), Ru1−O3 2.310(2), and O4−C24 1.172(4).
moderate enantioselectivity (Scheme 5). Although enantiose-
We evaluated the catalytic activity of the newly synthesized
CCN pincer Rh complexes in the asymmetric conjugate
reduction of β,β-disubstituted α,β-unsaturated carbonyl com-
pounds, which is a versatile method to construct compounds
with a β-chiral center.24 Recently, we reported that the phebox-
Rh acetate complex (phebox)Rh(OAc)2(H2O) served as an
efficient catalyst in asymmetric conjugate reductions of α,β-
unsaturated esters and ketones, with high enantioselectivity.2a,b
It was found that conjugate reduction of 11 with HSi(OEt)2Me
as a reducing reagent proceeded in the presence of 5b and
KOtBu to give the corresponding product 12 in high yield with
lectivity for 5b was lower than those of the phebox-Rh
Scheme 5. Asymmetric Conjugate Reduction of 11
D
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
complexes,2a the absolute configuration of 12 was opposite,
even with the use of the same chiral source of oxazoline unit.
Next, we elucidated the catalytic activity of the CCN Ru
complexes in the hydrogenation of ketones.25 Catalytic
hydrogenation of aromatic ketones 13 with Ru complexes 8
and 9 gave the corresponding alcohol in high yield with modest
enantioselectivity (Scheme 6). Although enantioselectivity was
lower than that with the phebox Ru complexes,3d,e bulky ketone
13b gave an R product 14b in 60% ee using 8a.
used as a catalyst precursor, 14c′ was selectively obtained in
84% yield (entry 4). The steric-hindered structure of 10 could
enhance the selectivity for hydrogenation of an anthracene ring.
In order to compare reactivity, we also performed hydro-
genation with the common catalysts Rh/C and Pd/C (entries 5
and 6). In the case of Pd/C, yields of alcohols were low, and
ketones 15b,c were predominantly obtained in 94% yield with a
ratio of 9:91 (entry 5). In contrast, the use of Rh/C afforded
alcohols 14c′−c″ (14c/14c′/14c″ = 0:12:88) and ketones
15a−c (15a/15b/15c = 33:67:0) in 51 and 48% yields,
respectively (entry 6). These traditional catalysts were found to
be less active than the CCN pincer Ru complexes toward
hydrogenation of a CO bond.
Scheme 6. Hydrogenation of Ketones Catalyzed by 8a−b
The catalytic hydrogenation of 13c by the phebox-Ru
complex under the same conditions gave alcohol 14c as the
single product.3e Hydrogenation with the BINAP/DPEN Ru
catalyst26 and hydrosilylation with DIPOF Rh catalyst27 showed
high selectivity toward the reduction of the CO bond of 13c.
In contrast, heterogeneous catalysts such as Rd/C, Rh/C, and
Rh nanoparticles have been reported as suitable catalysts for the
hydrogenation of anthracene.28 Several homogeneous Ru
complexes were also applied to diastereoselective and
enantioselective hydrogenation.29 CCN-Ru complexes 8 are
considered to have unique reactivity toward the hydrogenation
of both the CO bond and the anthracene ring.
In order to gain insight into hydrogenation, time courses of
the catalytic reaction of 13c with 8b were monitored (Figure
5). An increase in alcohol 14c was observed with decreasing
Hydrogenation of 9-acetylanthracene 13c using 8a was
unexpectedly found to give a mixture of 14c′ and 14c″ instead
of 14c (Table 1, entry 1). In this reaction, reduction of both
Table 1. Hydrogenation and Transfer Hydrogenation of
a
13c
yield (%), ratio of
14c′ ee
14c″ ee
entry
cat
8a
14c/14c′/14c″
(%)
(%)
1
2
3
4
99 (0:60:40)
99 (0:51:49)
97 (0:60:40)
90 (7:93:<1)
9 (R)
18 (R)
5 (R)
Figure 5. Time conversion of hydrogenation (30 atm) of 13c
catalyzed by 8b (1 mol %) and NaOEt (5 mol %) in 2-propanol at 40
°C.
8b
31 (R)
60 (R)
9b
28 (R)
10
b
c
5
Pd/C
Ph/C
6
b
d
6
51 (0:12:58)
13c, reaching a maximum after 3 h, then 14c′ and 14c″ were
simultaneously formed. This suggests that 14c is an
intermediate in the process forming 14c′ and 14c″.
a
Reaction conditions: 13c (1.0 mmol), catalyst (1 mmol %), NaOEt
b
(5 mmol %), 2-propanol (10 mL), 25 °C, 24 h. Reaction conditions:
13c (1.0 mmol), catalyst (1 mol %), NaOEt (5 mmol %), 2-propanol
(10 mL), 40 °C, 24 h. 15b,c were formed in 94% yield (15b/15c =
9:91). 15a−c were formed in 49% yield (15a/15b/15c = 33:67:0).
c
To check this reaction pathway, hydrogenation of racemic
14c was examined by using complexes 8b and 10 (Scheme 7).
The use of 8b as a catalyst gave a mixture of (R)-14c′ and (S)-
14c″ in 57 and 42% yields with 24% and 28% ee, respectively.
This result clearly indicates that hydrogenation of 14c afforded
14c′ and 14c″. The observed weak kinetic resolution suggests
that hydrogenation of an anthracene ring also proceeded on the
CCN Ru scaffold. In the case of 10, hydrogenation of 14c gave
14c′ in 85% yield as the major product. This selectivity was
similar to the hydrogenation of 13c catalyzed by 10. We also
confirmed the hydrogenation of anthracene by Ru catalysts
d
carbonyl and anthracene fragments proceeded to completion.
Use of 8b slightly increased enantioselectivity (entry 2).
Furthermore, coordination isomer 9b increased enantioselec-
tivity. This result indicates that the coordination environment
around a Ru center could affect enantioselectivity. In the case of
the chiral catalysts 8a, 8b, and 9b, the selectivity of 14c′ and
14c″ was low. In contrast, when the achiral complex 10 was
E
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
under the conditions of transfer hydrogenation. The selectivity
of the reduction of the anthracene ring was controlled by the
substituents of the CCN Ru complexes and the reducing
agents, H2 and 2-propanol.
Scheme 7. Hydrogenation of 14c Catalyzed by 8b and 10
EXPERIMENTAL SECTION
General Procedures. All air- and moisture-sensitive compounds
■
were manipulated using standard Schlenk and vacuum line techniques
1
under an argon atmosphere. H and 13C NMR spectra were obtained
1
at 25 °C on a Varian Mercury 300 spectrometer. H NMR chemical
shifts are reported in δ units, in ppm relative to the singlet at 7.26 ppm
for CDCl3, and 1.94 ppm for CD3CN. 13C NMR spectra are reported
in terms of chemical shifts relative to the triplet at 77.0 ppm for CDCl3
and 1.32 ppm for CD3CN. Infrared spectra were recorded on a JASCO
FT/IR-230 spectrometer. Elemental analyses were recorded on a
YANACO MT-6. Mass spectra were recorded on JEOL JMS-700.
Column chromatography was performed with silica gel column
chromatography (Kanto Kagaku Silica gel 60N).
under 30 atm of hydrogen at 100 °C, which yielded a mixture
of 17 and 18 (Scheme 8). This reaction was much slower than
those of 13c, indicating that the hydroxyl group of 14c could
enhance selectivity.
Scheme 8. Hydrogenation of 16 Catalyzed by 8a,b and 10
Preparation of 1. A mixture of 2,4-dimethylbenzoic acid (6.00 g,
40 mmol) and paraformaldehyde (3.01 g, 100 mmol) in AcOH (30
mL) and HCl (80 mL) was heated at 70 °C for 3 days. The resulting
precipitate was collected and washed with water and hexane. The
crude product was recrystallized from a mixture of hexane and ethyl
acetate to give compound 1 (5.29 g, 26.6 mmol, 67%).
1H NMR (300 MHz, CDCl3, rt): δ 2.46 (s, 3H), 2.64 (s, 3H), 4.62
(s, 2H), 7.13 (s, 1H), 8.05 (s, 1H), 11.63 (br, 1H). 13C{1H} NMR (75
MHz, CDCl3, rt): δ 19.0, 22.0, 44.2, 125.9, 133.0, 133.1, 134.3, 142.0,
142.6, 172.5. IR(KBr): 2976, 1694, 1612, 1560, 1280, 1255 cm−1. Anal.
Calcd for C10H11ClO2: C, 60.46; H, 5.58. Found: C, 60.02; H, 5.58.
HRMS (FAB, M = C10H11ClO2, m/z): Calcd for [M]+, 198.0448.
Found: 198.0444.
CCN-Ru complexes showed catalytic activity in the transfer
hydrogenation of 13c.30 When reduction of 13c with 8b was
carried out under the conditions of transfer hydrogenation
using 2-propanol, reduction of ketone and anthracene
proceeded to give 14c in 91% yield with a 14c/14c′/14c″
ratio of 12:9:72 (Scheme 9). In this reaction, selectivity of the
Preparation of 2. A mixture of 1 (1.98 g, 10 mmol) and SOCl2
was refluxed for 1.5 h, and then excess SOCl2 was removed under
reduced pressure to give a white solid. This material was dissolved in
CH2Cl2 (20 mL), and the resulting solution was slowly dropped into a
CH2Cl2 solution (30 mL) of (S)-phenylglycinol (1.37 g, 10 mmol)
and triethylamine (7 mL) at 0 °C. After being stirred for 1 h at room
temperature, a CH2Cl2 solution (10 mL) of MeSO2Cl (1.2 mL) was
added at 0 °C. The mixture was stirred for 4 h and then quenched by a
K2CO3 aqueous solution (1 M, 40 mL). After extraction with ethyl
acetate, the extract was washed with brine and dried over MgSO4. The
crude mixture was purified by column chromatography on silica gel
with hexane/ethyl acetate (10:1) to give 2a (2.44 g, 8.2 mmol, 82%).
The use of 1 (1.980 g, 10.0 mmol) and (S)-valinol (1.04 g, 10 mmol)
gave 2b (2.08 g, 7.8 mmol, 78%), and the use of 1 (993 mg, 5.0 mmol)
and 2-amino-2-methylpropan-1-ol (446 mg, 5.0 mmol) gave 2c (890
mg, 3.5 mmol, 71%).
Scheme 9. Transfer Hydrogenation of 13c Catalyzed by 8b
and 10
1
anthracene ring was found to be different from that in its
hydrogenation by H2. Although the driving force behind the
selectivity is unclear, two products could be selectively obtained
under hydrogenation and transfer hydrogenation conditions.
Notably, reduction of an aromatic ring under transfer
hydrogenation is considered to be rare.
2a: H NMR (300 MHz, CDCl3, rt): δ 2.45 (s, 3H), 2.63 (s, 3H),
2
3
4.25 (dd, JHH = 8.7 Hz, JHH = 8.3 Hz, 1H), 4.62 (s, 2H), 4.79 (dd,
3
3
2JHH = 8.7 Hz, JHH = 10.2 Hz, 1H), 5.44 (dd, JHH = 8.3, 10.2 Hz,
1H), 7.13 (s, 1H), 7.26−7.41 (m, 5H), 7.92 (s, 1H). 13C{1H} NMR
(75 Hz, CDCl3, rt): δ 18.8, 22.0, 44.4, 70.4, 74.0, 124.5, 126.4, 127.3,
128.5, 131.3, 132.7, 133.6, 139.6, 139.9, 142.3, 164.3. IR (KBr): 3061,
3020, 2967, 2923, 2898, 1645, 1495, 1449, 1353, 1260, 1126, 1021,
951, 743, 700, cm−1. Anal. Calcd for C18H18ClNO: C, 72.11; H, 6.05;
N, 4.67. Found: C, 72.13; H, 6.15; N, 4.71. HRMS (FAB, M =
C18H18ClNO, m/z): Calcd for [M + H]+, 300.1155. Found: 300.1152.
2b: 1H NMR (300 MHz, CDCl3, rt): δ 0.95 (d, 3JHH = 6.6 Hz, 3H),
1.03 (d, 3JHH = 6.6 Hz, 3H), 1.78−1.93 (m, 1H), 2.40 (s, 3H), 2.57 (s,
3H), 4.04−4.15 (m, 2H), 4.27−4.40 (m, 1H), 4.59 (s, 2H), 7.07 (s,
1H), 7.75 (s, 1H). 13C{1H} NMR (75 Hz, CDCl3, rt): δ 18.4, 18.8,
19.0, 21.6, 33.0, 44.5, 69.3, 72.9, 125.1, 131.1, 132.6, 133.5, 139.3,
139.4, 162.9. IR (KBr): 2959, 1647, 1450, 1348, 1264, 1152, 1007,
965, 881 cm−1. Anal. Calcd for C15H20ClNO: C, 67.79; H, 7.58; N,
5.27. Found: C, 67.70; H, 7.76; N, 5.06. HRMS (FAB, M =
C15H201ClNO, m/z): Calcd for [M + H]+, 266.1312. Found: 266.1303.
2c: H NMR (300 MHz, CDCl3, rt): δ 1.39 (s, 6H), 2.41 (s, 3H),
2.53 (s, 3H), 4.06 (s, 2H), 4.58 (s, 2H), 7.06 (s, 1H), 7.73 (s, 1H). 13C
NMR (75 Hz, CDCl3, rt): δ 18.8, 21.4, 28.6, 44.4, 67.7, 78.5, 125.3,
CONCLUSIONS
■
The CCN pincer Rh complexes 5 were successively prepared
by reaction of 3 with RhCl3·3H2O, under heat, via cyclo-
metalation of both imidazolium and benzene fragments. A
similar cyclometalation method could be applied to synthesize
the CCN pincer Ru complexes, which were obtained by the
reaction of a p-cymene NHC Ru complex with NaOAc in
DMF. The Rh complexes 5 showed catalytic activity toward the
conjugate reduction of 11 with HSi(OEt)2Me. In addition, Ru
complexes 8−10 were used as catalysts for the hydrogenation
of ketones. In particular, reduction of 13c proceeded at both a
CO bond and an anthracene ring to give the alcohols 14c′
and 14c″. Reduction of an anthracene ring also proceeded
F
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
131.2, 132.7, 133.4, 139.0, 139.5, 161.9. Anal. Calcd for C14H18ClNO:
C, 66.79; H, 7.21; N, 5.56. Found: C, 66.70; H, 7.33; N, 5.48.
Preparation of 3. A mixture of 2a (99 mg, 0.33 mmol) and 1-
isopropylimidazole (73 mg, 0.66 mmol) in MeCN (3 mL) was stirred
at 60 °C for 24 h. After removal of the solvent, the crude product was
washed with ethyl acetate to give 3a (130 mg, 0.31 mmol, 94%) as a
white solid. A similar procedure by using 2b (54 mg, 0.20 mmol) gave
3b (62 mg, 0.17 mmol, 85%). Reaction of 2c (50 mg, 0.30 mmol) with
1-isopropylimidazole (33 mg, 0.15 mmol) gave 3c (53 mg, 0.15 mmol,
73%). Reaction of 2b (56 mg, 0.21 mmol) with 1-mesityl-1H-
imidazole (74 mg, 0.40 mmol) gave 3d (74 mg, 0.16 mmol, 76%).
3a: 1H NMR (300 MHz, CDCl3, rt): δ 1.61 (d, 3JHH = 6.9 Hz, 6H),
2.32 (s, 3H), 2.62 (s, 3H), 4.19 (t, 2JHH = 8.3 Hz, 3JHH = 8.3 Hz, 1H),
4.74 (dd, 2JHH = 8.3 Hz, 3JHH = 10.3 Hz, 1H), 4.86 (septet, 3JHH = 6.9
Hz, 1H), 5.39 (d, 3JHH = 8.3, 10.3 Hz, 1H), 5.64 (s, 2H), 6.96 (t, 3JHH
= 1.8 Hz, 1H), 7.13 (s, 1H), 7.25−7.39 (m, 6H), 7.79 (s, 1H), 11.30
(s, 1H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 19.3, 21.8, 23.3, 51.3,
53.4, 70.3, 74.1, 119.8, 120.8, 125.2, 126.3, 127.3, 128.0, 128.5, 131.6,
134.2, 136.8, 140.1, 140.6, 141.9, 164.0. HRMS (FAB, M =
C24H28ClN3O, rt): Calcd for [M − Cl]+, 374.2232. Found:
374.2231. Correct elemental analysis could not be obtained due to
hygroscopicity.
139.9, 163.0, 163.1, 180.9 (d, JRhC = 51 Hz). Anal. Calcd for
C29H41ClN3ORh: C, 59.44; H, 7.05; N, 7.17. Found: C, 59.34; H,
7.19; N, 7.02.
Preparation of 5. A mixture of 3a (41 mg, 0.10 mmol), RhCl3·
3H2O (41 mg, 0.15 mmol), and Et3N (100 μL) in MeCN (2 mL) was
stirred at 95 °C for 24 h. After removal of the solvent, the residue was
purified by column chromatography on silica gel with hexane/ethyl
acetate (3:2) to give 5a (13 mg, 0.022 mmol, 22%) as a yellow solid.
5a. 1H NMR (300 MHz, CDCl3, rt): δ 1.41 (d, 3JHH = 6.9 Hz, 3H),
1.43 (d, 3JHH = 6.6 Hz, 3H), 2.35 (s, 3H), 2.56 (s, 3H), 4.43 (dd, 2JHH
3
2
= 8.9 Hz, JHH = 11.2 Hz, 1H), 5.14−5.22 (m, 2H), 5.37 (d, JHH
=
2
3
15.6 Hz, 1H), 5.47 (d, JHH = 15.6 Hz, 1H), 5.67 (t, JHH = 10.8 Hz,
1H), 6.71 (s, 1H), 7.06 (d, 3JHH = 2.4 Hz, 1H), 7.13 (d, 3JHH = 2.1 Hz,
1H), 7.34−7.48 (m, 3H), 7.64−7.69 (m, 2H). 13C{1H} NMR (75
MHz, CDCl3, rt): δ 20.2, 20.6, 23.5, 24.0, 50.9, 51.1, 66.6, 118.2, 122.4,
127.8, 128.2, 128.8, 129.5, 133.7, 136.6, 138.4, 138.9, 152.2 (d, 1JRnC
=
1
33 Hz), 162.2 (d, JRnC = 43 Hz), 172.8. Anal. Calcd for
C24H28Cl2N3O2Rh: C, 51.08; H, 5.00; N, 7.45. Found: C, 51.51; H,
4.88; N, 7.33.
1
3
5b. H NMR (300 MHz, CD3CN, rt): δ 0.87 (d, JHH = 6.3 Hz,
3H), 1.01 (d, 3JHH = 7.2 Hz, 3H), 1.40 (d, 3JHH = 6.8 Hz, 3H), 1.53 (d,
3JHH = 6.8 Hz, 3H), 2.36 (s, 3H), 2.41 (m, 1H), 2.47 (s, 3H), 4.44−
3b: 1H NMR (300 MHz, CDCl3, rt): δ 0.86 (d, 3JHH = 6.6 Hz, 3H),
0.94 (d, 3JHH = 6.9 Hz, 3H),1.54 (d, 3JHH = 6.9 Hz, 6H), 1.75 (m, 1H),
2.20 (s, 3H), 2.47 (s, 3H), 3.96−4.06 (m, 2H), 4.23−4.32 (m, 1H),
4.80 (m, 1H), 5.12 (s, 2H), 6.94 (s, 1H), 7.01 (s, 1H), 7.58 (s, 1H),
7.61 (s, 1H), 10.92 (s, 1H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ
16.6, 17.0, 17.3, 19.6, 21.3, 31.0, 48.7, 51.2, 67.4, 70.9, 119.3, 119.8,
123.5, 126.6, 128.4, 131.8, 133.6, 137.2, 137.8, 160.2. IR (KBr): 2978,
1647, 1558, 1458, 1350, 1152, 951, 888, 757 cm−1. Anal. Calcd for
C21H30ClN3O(H2O): C, 64.02; H, 8.19; N, 10.67. Found: C, 64.57; H,
8.28; N, 10.71. HRMS (FAB, M = C21H30N3O, m/z): Calcd for [M −
Cl]+, 340.2389. Found: 340.2390.
3
4.48 (m, 1H), 4.59−4.71 (m, 2H), 5.37 (s, 2H), 5.63 (septet, JHH
=
=
6.8 Hz, 1H), 6.69 (s, 1H), 7.27 (d, 3JHH = 2.0 Hz, 1H), 7.35 (d, 3JHH
2.0 Hz, 1H). 13C{1H} NMR (75 MHz,. CD3CN, rt): δ 16.0, 19.6, 20.2,
20.5, 23.9, 24.6, 31.3, 51.5, 68.2, 72.0, 118.3, 118.5, 124.1, 129.1, 131.0,
135.8, 136.4, 137.3, 162.0 (d, 1JRnC = 43 Hz), 163.4 (d, 1JRnC = 27 Hz),
2
173.0 (d, JRnC = 2.3 Hz). Anal. Calcd for C42H56Cl4N6O2Rh2: C,
49.24; H, 5.51; N, 8.20. Found: C, 49.24; H, 5.43; N, 8.12.
5d. 1H NMR (300 MHz, CDCl3, rt): δ 0.87 (d, 3JHH = 6.9 Hz, 3H),
2.14−2.22 (m, 1H), 2.30 (s, 6H), 2.35 (s, 3H), 2.38 (s, 3H), 2.48 (s,
2
3
3H), 4.10−4.21 (m, 1H), 4.47 (t, JHH = 8.3 Hz, JHH = 8.3 Hz, 1H),
4.66 (dd, 2JHH = 8.7 Hz, 3JHH = 9.9 Hz, 1H), 5.53 (d, JHH = 15.9 Hz,
2
3c: 1H NMR (300 MHz, CDCl3, rt): δ 1.33 (s, 6H), 1.58 (d, 3JHH
=
2
3
1H), 5.61 (d, JHH = 15.9 Hz, 1H), 6.68 (s, 1H), 6.99 (d, JHH = 2.0
6.8 Hz, 6H), 2.24 (s, 3H), 2.48 (s, 3H), 4.02 (s, 2H), 4.86 (septet, 3JHH
3
Hz, 1H), 7.03 (s, 1H), 7.04 (s, 1H), 7.32 (d, JHH = 2.0 Hz, 1H).
3
4
= 6.8 Hz, 1H), 5.55 (s, 2H), 6.95 (t, JHH = 1.8 Hz, JHH = 1.8 Hz,
1H), 7.04 (s, 1H), 7.51 (t, 3JHH = 1.8 Hz, 4JHH = 1.8 Hz, 1H), 7.63 (s,
13C{1H} NMR (75 MHz, CDCl3, rt): δ 16.2, 18.9, 19.2, 20.0, 20.1,
20.5, 21.3, 30.0, 51.5, 67.1, 71.4, 122.8, 123.3, 128.5, 128.9, 129.4,
129.5, 129.6, 132.7, 135.5, 135.9, 137.0, 137.3, 137.8, 139.4, 149.9 (d,
4
1H), 11.07 (d, JHH = 1.8 Hz, 1H). 13C{1H} NMR (75 MHz, CDCl3,
rt): δ 19.1, 21.3, 23.2, 28.5, 51.2, 53.3, 67.7, 78.5, 119.9, 120.7, 125.8,
127.7, 131.4, 134.0, 136.5, 139.6, 140.1, 161.4. Correct elemental
analysis could not be obtained due to hygroscopicity.
1JRnC = 34 Hz), 166.3 (d, JRnC = 44 Hz), 170.5 (d, JRnC = 2 Hz),
171.2. Anal. Calcd for C27H34Cl2N3O2Rh: C, 53.48; H, 5.65; N, 6.93.
Found: C, 53.96; H, 5.46; N, 7.50.
1
2
3d: 1H NMR (300 MHz, CDCl3, rt): δ 0.86 (d, 3JHH = 6.6 Hz, 3H),
0.94 (d, 3JHH = 6.6 Hz, 3H), 1.76 (m, 1H), 1.97 (s, 6H), 2.23 (s, 6H),
2.48 (s, 3H), 3.94−4.04 (m, 2H), 4.20−4.30 (m, 1H), 5.84 (s, 1H),
6.87 (s, 2H), 7.00 (s, 1H), 7.23 (s, 1H), 7.33 (s, 1H), 7.58 (s, 1H),
10.68 (s, 1H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 17.2, 17.5, 18.2,
18.8, 19.1, 21.0, 21.4, 32.8, 51.6, 69.2, 72.7, 121.8, 123.3, 125.3, 128.2,
129.4, 130.3, 130.8, 133.6, 134.0, 138.1, 139.5, 140.1, 140.7, 162.3. IR
(KBr): 2958, 1645, 1547, 1457, 1348, 1202, 1033, 855, 751 cm−1.
Anal. Calcd for C30H32ClN3O(H2O): C, 68.99; H, 7.72; N, 8.94.
Found: C, 68.64; H, 7.54; N, 8.92. HRMS (FAB, M = C30H32ClN3O,
m/z): Calcd for [M − Cl]+, 416.2702. Found: 416.2704.
Preparation of 6. A mixture of 3a (249 mg, 0.61 mmol) and Ag2O
(71 mg, 0.31 mmol) in CH2Cl2 (2 mL) was stirred at room
temperature for 8 h. After filtration through Celite, the solvent was
removed under reduced pressure. The crude product was washed with
ethyl acetate to give 5a (245 mg, 0.27 mmol, 89%) as a white solid.
Reaction of 3b (884 mg, 2.4 mmol) with Ag2O (278 mg, 1.2 mmol)
gave 6b (923 mg, 1.1 mmol, 92%) as a white solid. Reaction of 3c
(36.2 mg, 0.10 mmol) with Ag2O (12.2 mg, 0.050 mmol) gave 6c
(35.2 mg, 0.044 mmol, 89%) as a white solid.
1
3
6a. H NMR (300 MHz, CDCl3, rt): δ 1.46 (d, JHH = 6.9 Hz,
12H), 2.22 (s, 6H), 2.60 (s, 6H), 4.16 (dd, JHH = 8.2 Hz, JHH = 8.6
Hz, 2H), 4.66−4.76 (m, 4H), 5.22 (s, 4H), 5.38 (dd, JHH = 8.6, 10.3
2
3
Preparation of 4. A mixture of 3b (1.08 g, 2.88 mmol) and
[Rh(cod) (OH)]2 (658 mg, 1.44 mmol) in THF (20 mL) was stirred
at room temperature for 11 h. After removal of the solvent, the crude
product was purified by column chromatography on silica gel with
hexane/ethyl acetate (1:1) to give 4 (950 mg, 1.62 mmol) as a yellow
solid.
3
3
3
Hz, 2H), 6.76 (d, JHH = 1.8 Hz, 2H), 6.98 (d, JHH = 1.8 Hz, 2H),
7.09 (s, 2H), 7.22−7.35 (m, 10H), 7.63 (s, 2H). 13C{1H} NMR (75
Hz, CDCl3, rt): δ 19.5, 21.8, 23.9, 53.7, 54.3, 70.3, 74.0, 117.3, 120.5,
124.8, 126.3, 127.2, 128.4, 130.2, 130.7, 133.9, 139.4, 139.7, 142.1,
164.1, 177.6. IR (KBr): 3123, 3027, 2973, 1638, 1453, 1351, 1131,
1017, 945, 748. 702 cm−1. HRMS (FAB, M = C48H54ClN6O2Ag, m/z):
Calcd for [M − Cl]+, 853.3359. Found: 853.3337. Correct elemental
analysis could not be obtained after several attempts due to
hygroscopicity.
3
1H NMR (300 MHz, CDCl3, rt): δ 0.94 (d, JHH = 6.3 Hz, 3H),
3
3
1.02 (d, JHH = 6.9 Hz, 1.5H), 1.03 (d, JHH = 6.9 Hz, 1.5H), 1.49 (d,
3JHH = 6.6 Hz, 3H), 1.52 (d, JHH = 6.3 Hz, 3H), 1.80−2.05 (m, 5H),
3
2.20−2.52 (m, 7H), 2.57 (s, 3H), 3.26−3.42 (m, 2H), 4.03−4.16 (m,
2H), 4.29−4.36 (m, 1H), 4.96−5.12 (m, 2H), 5.60−5.83 (m, 3H),
6.50 (d, 3JHH = 1.8 Hz, 0.5H), 6.52 (d, 3JHH = 1.8 Hz, 0.5 H), 6.80 (d,
3JHH = 1.8 Hz, 0.5H), 6.81 (d, 3JHH = 1.8 Hz, 0.5 H), 7.11 (s, 1H), 7.58
(s, 0.5H), 7.59 (s, 0.5H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 18.4,
18.5, 18.97, 19.04, 19.7, 21.4, 21.5, 23.4, 24.4, 28.5, 29.4, 32.6, 33.05,
33.07, 33.5, 52.5, 52.6, 52.7, 67.4, 67.6, 68.1, 68.2, 69.4, 69.5, 72.9,
73.0, 97.7, 97.8, 98.5, 98.6, 115.99, 116.01, 120.2, 120.3, 125.18,
125.22, 130.77, 130.87, 130.92, 131.0, 133.6, 138.7, 138.8, 139.8,
6b. 1H NMR (300 MHz, CDCl3, rt): δ 0.94 (d, 3JHH = 6.9 Hz, 3H),
3
3
1.02 (d, JHH = 6.6 Hz, 3H), 1.47 (d, JHH = 6.9 Hz, 6H), 1.78−1.89
(m, 1H), 2.21 (s, 3H), 2.55 (s, 3H), 4.04−4.14 (m, 2H), 4.32−4.37
(m, 1H), 4.74 (septet, 3JHH = 6.9 Hz, 1H), 5.22 (s, 2H), 6.74 (d, 3JHH
= 2.0 Hz, 1H), 6.97 (d, 3JHH = 2.0 Hz, 1H), 7.08 (s, 1H), 7.54 (s, 1H).
13C{1H} NMR (75 Hz, CDCl3, rt): δ 17.4, 17.8, 18.3, 20.4, 22.7, 31.7,
52.0, 52.9, 68.1, 71.6, 116.7, 120.0, 123.9, 128.7, 129.9, 132.3, 137.5,
G
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
161.1, 177.2. HRMS (FAB, M = C42H58ClN6O2Ag, m/z): Calcd for
[M − Cl]+, 785.3672. Found: 785.3687. Correct elemental analysis
could not be obtained due to high hygroscopicity.
23.0, 23.9, 24.1, 50.4, 52.8, 68.1, 78.3, 116.1, 122.4, 127.0, 127.4, 128.2,
128.5, 130.6, 133.9, 135.3, 137.2, 141.9, 168.8, 175.2, 179.5, 184.9,
202.0. IR (KBr): 1894 (νCO) cm−1. Anal. Calcd for C27H29N3O4Ru: C,
57.85; H, 5.21; N, 7.50. Found: C, 57.94; H, 4.92; N, 7.25.
6c. 1H NMR (300 MHz, CDCl3, rt): δ 1.37 (s, 6H), 1.45 (d, 3JHH
=
6.6 Hz, 6H), 2.19 (s, 3H), 2.52 (s, 3H), 4.04 (s, 2H), 4.72 (septet, 3JHH
= 6.6 Hz, 1H), 5.21 (s, 2H), 6.72 (d, 3JHH = 2.1 Hz, 1H), 6.96 (d, 3JHH
= 2.1 Hz, 1H), 7.05 (s, 1H), 7.54 (s, 1H). 13C{1H} NMR (75 MHz,
CDCl3, rt): δ 19.6, 21.3, 23.9, 28.6, 53.9, 54.3, 67.8, 78.5, 117.2, 120.4,
125.7, 129.9, 130.9, 133.8, 139.2, 139.4, 161.7. HRMS (FAB, M =
C40H54N6O2Ag, m/z): Calcd for [M − Cl]+, 757.3359. Found:
757.3344. Correct elemental analysis could not be obtained due to
high hygroscopicity.
8b. 1H NMR (300 MHz, CDCl3, rt): δ 0.84 (d, 3JHH = 6.6 Hz, 3H),
0.95 (d, 3JHH = 7.2 Hz, 3H), 1.42 (d, 3JHH = 6.6 Hz, 3H), 1.46 (d, 3JHH
= 6.6 Hz, 3H), 1.83 (s, 3H), 2.26 (s, 3H), 2.45 (s, 3H), 4.33−4.66 (m,
3
3H), 5.18−5.34 (m, 3H), 6.59 (s, 1H), 7.01 (d, JHH = 2.2 Hz, 1H),
3
7.09 (d, JHH = 1.2 Hz, 1H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ
14.9, 19.9, 20.3, 20.5, 24.0, 24.1, 24.2, 29.4, 50.6, 52.8, 69.3, 70.0,
116.2, 122.3, 128.3, 130.8, 133.6, 135.0, 136.8, 167.7, 173.9, 179.7,
184.3, 202.2. IR (KBr): 1884 (νCO) cm−1. Anal. Calcd for
C24H31N3O4Ru: C, 54.74; H, 5.93; N, 7.98. Found: C, 55.03; H,
6.21; N, 7.62.
Preparation of 7. A mixture of 6a (203 mg, 0.23 mmol) and
[RuCl2(p-cymene)]2 (141 mg, 0.23 mmol) in THF (20 mL) was
stirred at 60 °C for 24 h. After filtration through Celite, the solvent
was removed under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/ethyl acetate (1:4)
to give 7a (234 mg, 0.34 mmol, 75%) as a dark brown solid. A similar
procedure by using 6b (116 mg, 0.14 mmol) and 6c (356 mg, 0.45
mmol) gave 7b (93 mg, 0.14 mmol, 49%) and 7c (352 mg, 0.56 mmol,
62%), respectively.
9a. 1H NMR (300 MHz, CDCl3, rt): δ 1.33 (d, 3JHH = 6.3 Hz, 3H),
3
1.35 (d, JHH = 6.6 Hz, 3H), 1.94 (s, 3H), 2.32 (s, 3H), 2.54 (s, 3H),
4.60−4.65 (m, 1H), 4.98−5.21 (m, 5H), 6.62 (s, 1H), 6.94 (d, 3JHH
=
3
1.8 Hz, 1H), 7.05 (d, JHH = 1.8 Hz, 1H), 7.30−7.41 (m, 5H).
13C{1H} NMR (75 MHz, CDCl3, rt): δ 20.2, 20.5, 24.1, 24.2, 49.9,
52.5, 65.3, 77.2, 115.8, 122.4, 126.9, 127.8, 128.0, 128.6, 130.0, 134.3,
135.7, 137.6, 140.3, 173.7, 178.9, 184.2, 201.8. IR (KBr): 1905 (νCO
)
7a. 1H NMR (300 MHz, CDCl3, rt): δ 1.18 (d, 3JHH = 6.6 Hz, 3H),
1.15 (d, 3JHH = 5.4 Hz, 3H), 1.42 (d, 3JHH = 6.9 Hz, 3H), 1.49 (d, 3JHH
= 5.7 Hz, 3H), 1.97 (d, 3JHH = 8.7 Hz, 3H), 2.34 (s, 3H), 2.62 (s, 3H),
cm−1. Anal. Calcd for C27H29N3O4Ru0.5(H2O): C, 56.93; H, 5.31; N,
7.38. Found: C, 57.00; H, 5.09; N, 7.30.
9b. 1H NMR (300 MHz, CDCl3, rt): δ 0.99 (d, 3JHH = 6.9 Hz, 3H),
1.01 (d, 3JHH = 6.9 Hz, 3H), 1.39 (d, 3JHH = 6.6 Hz, 3H), 1.46 (d, 3JHH
= 6.6 Hz, 3H), 1.93 (s, 3H), 2.29 (s, 3H), 2.36−2.42 (m, 1H), 2.47 (s,
3H), 4.05−4.11 (m, 1H), 4.52−4.65 (m, 2H), 5.05 (d, 2JHH = 15.8 Hz,
2
3
2.66−2.79 (m, 1H), 4.19 (br, 1H), 4.72 (dd, JHH = 8.3 Hz, JHH
=
10.1 Hz, 1H), 5.05−5.40 (m, 8H), 6.00 (d, 2JHH = 16.2 Hz, 1H), 6.86
(s, 1H), 7.08−7.34 (m, 7H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ
18.2, 19.3, 21.5, 22.5, 22.9, 24.8, 25.3, 30.8, 52.4, 52.6, 70.1, 74.0, 83.2,
83.4, 84.3, 84.7, 85.0, 85.3, 95.7, 106.4, 118.8, 123.5, 126.3, 127.3,
127.7, 128.4, 133.5, 134.0, 138.0, 138.4, 142.2, 164.5, 173.6. Anal.
Calcd for C34H41ClN3ORu: C, 60.08; H, 6.08; N, 6.18. Found: C,
59.66; H, 6.45; N, 5.79. HRMS (FAB, M = C34H41ClN3ORu, m/z):
Calcd for [M − Cl]+, 644.1982. Found: 644.1964.
2
3
1H), 5.21 (d, JHH = 15.8 Hz, 1H), 5.33 (septet, JHH = 6.6 Hz, 1H),
6.58 (s, 1H), 6.99 (d, 3JHH = 2.0 Hz, 1H), 7.07 (d, 3JHH = 2.0 Hz, 1H).
13C{1H} NMR (75 MHz, CDCl3, rt): δ 15.6, 19.2, 20.2, 20.4, 24.1,
24.2, 29.8, 50.1, 52.7, 66.0, 70.3, 115.9, 122.4, 128.0, 130.2, 134.2,
135.2, 137.1, 171.8, 172.6, 179.1, 184.3, 202.2. IR (KBr): 1898 (νCO
)
cm−1. Anal. Calcd for C24H31N3O4Ru: C, 54.74; H, 5.93; N, 7.98.
Found: C, 54.43; H, 6.27; N, 7.99.
7b. 1H NMR (300 MHz, CDCl3, rt): δ 0.92 (d, 3JHH = 6.6 Hz, 3H),
1.00 (d, 3JHH = 6.6 Hz, 3H), 1.19 (d, 3JHH = 6.9 Hz, 3H), 1.27 (d, 3JHH
10. 1H NMR (300 MHz, CDCl3, rt): δ 1.42 (d, 3JHH = 6.8 Hz, 3H),
1.466 (s, 3H), 1.471 (d, 3JHH = 6.8 Hz, 3H), 1.60 (s, 3H), 1.85 (s, 3H),
3
= 6.6 Hz, 3H), 1.51 (d, JHH = 6.6 Hz, 6H), 1.73−1.86 (m, 1H), 2.00
(s, 3H), 2.32 (s, 3H), 2.55 (s, 3H), 2.74 (septet, JHH = 6.9 Hz, 1H),
3
2.27 (s, 3H), 2.46 (s, 3H), 4.35 (d, 2JHH = 8.3 Hz, 1H), 4.47 (d, 2JHH
=
4.00−4.15 (m, 2H), 4.28−4.35 (m, 1H), 5.05−5.43 (m, 6H), 6.03 (d,
3
8.3 Hz, 1H), 5.25 (s, 1H), 5.29 (septet, JHH = 6.8 Hz, 1H), 6.58 (s,
2JHH = 17.1 Hz, 1H), 6.86 (d, 3JHH = 1.7 Hz, 1H), 6.97−7.02 (br, 1H),
3
3
1H), 7.01 (d, JHH = 2.1 Hz, 1H), 7.09 (d, JHH = 2.1 Hz, 1H).
13C{1H} NMR (75 MHz, CDCl3, rt): δ 20.3, 20.5, 24.1, 24.20, 24.21,
27.3, 27.6, 50.4, 52.8, 65.3, 81.5, 116.2, 122.4, 128.2, 131.2, 133.9,
3
7.10 (s, 1H), 7.11 (d, JHH = 1.7 Hz, 1H). 13C{1H} NMR (75 MHz,
CDCl3, rt): δ 18.4, 18.6, 19.0, 21.3, 22.6, 22.9, 24.8, 25.4, 30.9, 33.1,
52.4, 52.7, 69.3, 69.7, 72.9, 80.0, 83.5, 84.3, 84.7, 85.0, 95.7, 106.2,
118.8, 123.6, 125.1, 127.1, 127.3, 133.3, 133.9, 137.7, 163.2, 173.6.
HRMS (FAB, M = C31H43ClN3ORu, m/z): Calcd for [M − Cl]+,
610.2138. Found: 610.2123.
134.7, 136.9, 168.4, 172.5, 179.6, 184.4, 202.4. IR (KBr): 1896 (νCO
)
cm−1. Anal. Calcd for C23H29N3O4Ru: C 53.90; H 5.70; N 8.20.
Found: C 54.11; H 5.87; N 7.98.
7c. 1H NMR(300 MHz, CDCl3, rt): δ 1.21 (d, 3JHH = 8.4 Hz, 3H),
1.28 (d, 3JHH = 6.6 Hz, 3H), 1.35 (s, 6H), 1.52 (d, 3JHH = 6.9 Hz, 6H),
1.70 (m, 1H), 2.02 (s, 3H), 2.32 (s, 3H), 2.54 (s, 3H), 2.78 (sept, 3JHH
= 6.9 Hz, 1H), 4.02 (s, 2H), 5.05 (m, 1H), 5.21 (m, 2H), 5.47−5.30
Catalytic Conjugate Reduction. To a toluene solution (1 mL) of
11 (176 mg, 0.93 mmol) in the presence of 5b (4.7 mg, 0.0088 mmol)
and KOtBu (3.3 mg, 0.29 mmol) was added HSiMe(OEt)2 (191 mg,
1.42 mmol) at 60 °C. The reaction mixture was stirred at 60 °C for 1
h. After removal of the solvent under reduced pressure, the residue was
dissolved in MeOH (1 mL) and THF (1 mL) and was treated with
hydrochloric acid (1 M, 1 mL) at 0 °C. After being stirred for 1 h at 0
°C, the mixture was extracted with ethyl acetate, and the extract was
concentrated. The residue was purified by silica-gel chromatography
with hexane/ethyl acetate (99:1) to give the product (S)-12 (162 mg,
0.84 mmol, 84%) as a colorless oil. Chiral HPLC (Daicel Chiralcel
OB-H, hexane/2-propanol, 99:1, 0.5 mL/min), tR = 6.5 min (minor),
2
3
(m, 3H), 5.91 (d, JHH = 16.8 Hz, 1H), 6.83 (d, JHH = 2.1 Hz, 1H),
7.00 (s, 1H), 7.10 (d, JHH = 2.1 Hz, 2H). 13C{1H} NMR(75 MHz,
3
CDCl3): δ 18.5, 19.3, 21.1, 22.5, 23.1, 24.8, 25.5, 28.7, 31.0, 52.4, 52.8,
67.8, 78.4, 83.6, 84.4, 84.6, 84.9, 96.0, 106.2, 118.7, 123.5, 125.3, 127.7,
133.3, 133.8, 137.7, 138.1, 161.9, 173.7. HRMS (FAB, M =
C30H41ClN3ORu, m/z): Calcd for [M − Cl]+, 596.1982. Found:
596.1988.
Preparation of 8−10. A mixture of 7a (136 mg, 0.20 mmol) and
sodium acetate (82 mg, 1.0 mmol) in DMF (10 mL) was stirred at 80
°C for 5 h. After removal of the solvent, the residue was purified by
column chromatography on silica gel with hexane/ethyl acetate (1:4)
to give 8a (75 mg, 0.13 mmol, 67%) and 9a (15 mg, 0.027 mmol,
13%). Reaction of 7b (117 mg, 0.18 mmol) with NaOAc (81 mg,
0.98) gave 8b (52 mg, 0.099 mmol, 50%) and 9b (29 mg, 0.054 mmol,
27%). Reaction of 7c (126 mg, 0.20 mmol) with NaOAc (83 mg, 1.0
mmol) gave 10 (59 mg, 0.12 mmol, 58%).
7.7 min (major). [α]D = +4.8 (c = 0.97 in CHCl3); lit.31 [α]D
=
27
25
+19 (c = 1.1 in CHCl3), 90% ee for S.
Catalytic Hydrogenation. A stainless steel autoclave was charged
with catalysts (0.005 mmol), NaOEt (0.025 mmol) and ketone 13 (0.5
mmol). After the addition of 2-propanol (5 mL) under an Ar
atmosphere, the H2 pressure was adjusted to 30 atm. The reaction
mixture was stirred at 40 °C for 24 h, and then the solvent was
removed under reduced pressure. The residue was purified by column
chromatography on silica gel with hexane/ethyl acetate (6:1). The
ratio of products was calculated by 1H NMR. The enantioselectivity of
products was determined by using HPLC with a proper chiral column.
Enantiopure compounds 14c′ and 14c″ were prepared by
hydrogenation of (S)-14c (99% ee)3e with Pd/C (1 mol %) in 2-
8a. 1H NMR (300 MHz, CDCl3, rt): δ 0.84 (s, 3H), 1.30 (d, 3JHH
=
3
6.6 Hz, 3H), 1.41 (d, JHH = 6.6 Hz, 3H), 2.29 (s, 3H), 2.52 (s, 3H),
4.50 (dd, 3JHH = 6.5 Hz, 2JHH = 8.9 Hz, 1H), 5.04−5.35 (m, 5H), 6.63
3
3
(s, 1H), 6.98 (d, JHH = 1.8 Hz, 1H), 7.08 (d, JHH = 1.8 Hz, 1H),
7.25−7.37 (m, 5H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 20.4, 20.6,
H
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
propanol under 30 atm of H2. The crude products were purified by
column chromatography on silica gel and recycle LC.
ACKNOWLEDGMENTS
■
This research was supported by a Grant-in-Aid for Scientific
Research from the Japan Society for the Promotion of Science
(Nos. 26410114 and 15H03808).
(S)-1-(1,2,3,4-Tetrahydroanthracene-9-yl)ethanol (14c′). 1H
NMR (300 MHz, CDCl3) δ 1.74−1.97 (m, 7H), 2.84−3.13 (m, 4H),
3
5.82 (dq, JHH = 2.0, 6.8 Hz, 1H), 7.34−7.41 (m, 2H), 7.51 (s, 1H),
7.70−7.73 (m, 1H), 8.69−8.71 (m, 1H). 13C{1H} NMR (75 MHz,
CDCl3, rt): δ 22.5, 22.6, 23.8, 27.1, 30.9, 67.0, 124.2, 124.4, 125.5,
127.2, 127.7, 129.2, 132.58, 132.64, 135.5, 136.6. HRMS (FAB, M =
C16H18O, m/z): Calcd for [M + Na]+, 249.1255. Found: 249.1251.
REFERENCES
■
(1) (a) Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001, 40,
3750−3781. (b) van der Boom, M. E.; Milstein, D. Chem. Rev. 2003,
103, 1759−1792. (c) Choi, J.; MacArthur, A. H. R.; Brookhart, M.;
Goldman, A. S. Chem. Rev. 2011, 111, 1761−1779. (d) Selander, N.;
Szabo, K. J. Chem. Rev. 2011, 111, 2048−2076. (e) Singleton, J. T.
Tetrahedron 2003, 59, 1837−1857. (e1) Gunanathan, C.; Milstein, D.
Chem. Rev. 2014, 114, 12024−12087. (f) Younus, H. A.; Su, W.;
Ahmad, N.; Chen, S.; Verpoort, F. Adv. Synth. Catal. 2015, 357, 283−
330. (g) Nishiyama, H.; Ito, J. Chem. Commun. 2010, 46, 203−212.
(h) Ito, J.; Nishiyama, H. Synlett 2012, 23, 509−523.
(2) (a) Kanazawa, Y.; Tsuchiya, Y.; Kobayashi, K.; Shiomi, T.; Itoh,
J.; Kikuchi, M.; Yamamoto, Y.; Nishiyama, H. Chem. - Eur. J. 2006, 12,
63−71. (b) Itoh, K.; Tsuruta, A.; Ito, J.; Yamamoto, Y.; Nishiyama, H.
J. Org. Chem. 2012, 77, 10914−10919. (c) Toribatake, K.; Nishiyama,
H. Angew. Chem., Int. Ed. 2013, 52, 11011−11015. (d) Toribatake, K.;
Zhou, L.; Tsuruta, A.; Nishiyama, H. Tetrahedron 2013, 69, 3551−
3560. (e) Toribatake, K.; Miyata, S.; Naganawa, Y.; Nishiyama, H.
Tetrahedron 2015, 71, 3203−3208. (f) Ohshima, T.; Kawabata, T.;
Takeuchi, Y.; Kakinuma, T.; Iwasaki, T.; Yonezawa, T.; Murakami, H.;
Nishiyama, H.; Mashima, K. Angew. Chem., Int. Ed. 2011, 50, 6296−
6300. (g) Morisaki, K.; Sawa, M.; Nomaguchi, J.; Morimoto, H.;
Takeuchi, Y.; Mashima, K.; Ohshima, T. Chem. - Eur. J. 2013, 19,
8417−8420.
25
[α]D = −30.8 (c 1.00, CHCl3, 99% ee (S)). Chiral HPLC (Daicel
Chiralpak AS-H, hexane/2-propanol, 95:5, 0.8 mL/min), tR = 10.5 min
(S), 12.0 min (R).
1
(S)-1-(9,10-Dihydroanthracene-9-yl)ethanol (14c″). H NMR
3
(300 MHz, CDCl3): δ 1.15 (d, JHH = 6.0 Hz, 3H), 1.59 (s, 1H),
3.84−3.90 (m, 3H), 4.16 (d, 2JHH = 18.6 Hz, 1H), 7.21−7.35 (m, 8H).
13C{1H} NMR (75 MHz, CDCl3, rt): δ 20.6, 35.9, 55.4, 70.7, 125.91,
125.93, 126.4, 126.6, 127.6, 127.9, 128.9, 129.0, 136.3, 136.4, 136.6,
136.7. HRMS (FAB, M = C16H16O, m/z): Calcd for [M + Na]+,
25
247.1099. Found: 247.1095. [α]D = −14.0 (c 1.00, CHCl3, 99% ee
(S)). Chiral HPLC (Daicel Chiralpak AD-H, hexane/2-propanol, 95:5,
0.8 mL/min): tR = 15.1 min (S), 16.6 min (R).
1,2,3,4,5,6,7,8-Octahydro-9-acethylanthracene (15a). 1H
NMR (300 MHz, CDCl3, rt) δ 1.74−1.79 (m, 8H), 2.46 (s, 3H),
2.57 (br, 4H), 2.73 (br, 4H), 6.81 (s, 1H). 13C{1H} NMR (75 MHz,
CDCl3, rt): δ 23.0, 23.2, 26.4, 29.4, 32.2, 128.2, 129.9, 134.5, 142.2,
209.2. HRMS (FAB, M = C16H20O, m/z): Calcd for [M + Na]+,
251.1412. Found: 251.1405.
1,2,3,4-Tetrahydro-9-acethylanthracene (15b). 1H NMR (300
MHz, CDCl3, rt): δ 1.84−1.92 (m, 4H), 2.63 (s, 3H), 2.84 (m, 2H),
3.00 (m, 2H), 7.38−7.43 (m, 2H), 7.52−7.55 (m, 1H), 7.58 (s, 1H),
7.72−7.76 (m, 1H). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 22.9, 23.1,
27.1, 30.2, 33.0, 123.4, 125.2, 125.6, 127.1, 127.3, 127.5, 130.2, 131.5,
135.6, 138.4, 208.4. HRMS (FAB, M = C16H16O, m/z): Calcd for [M
+ Na]+, 247.1099. Found: 247.1090.
(3) (a) Ito, J.; Fujii, K.; Nishiyama, H. Chem. - Eur. J. 2013, 19, 601−
605. (b) Ito, J.; Ujiie, S.; Nishiyama, H. Chem. - Eur. J. 2010, 16, 4986−
4990. (c) Ito, J.; Asai, R.; Nishiyama, H. Org. Lett. 2010, 12, 3860−
3862. (d) Ito, J.; Ujiie, S.; Nishiyama, H. Organometallics 2009, 28,
630−638. (e) Ito, J.; Teshima, T.; Nishiyama, H. Chem. Commun.
2012, 48, 1105−1107.
9,10-Dihydro-9-acethylanthracene (15c). 1H NMR (300 MHz,
CDCl3, rt): δ 2.05 (s, 3H), 4.00 (d, 2JHH = 19.0 Hz, 1H), 4.22 (d, 2JHH
= 19.0 Hz, 1H), 5.03 (s, 1H), 7.25−7.37 (m, 8H). 13C{1H} NMR (75
MHz, CDCl3, rt): δ 27.3, 35.3, 61.5, 126.4, 127.3, 128.07, 128.09,
133.1, 135.3, 205.0. HRMS (FAB, M = C16H14O, m/z): Calcd for [M
+ Na]+, 245.0942. Found: 245.0940.
(4) (a) Hao, X.-Q.; Gong, J.-F.; Du, C.-X.; Wu, L.-Y.; Wu, Y.-J.; Song,
M.-P. Tetrahedron Lett. 2006, 47, 5033−5036. (b) Wu, L.-Y.; Hao, X.-
Q.; Xu, Y.-X.; Jia, M.-Q.; Wang, Y.-N.; Gong, J.-F.; Song, M.-P.
Organometallics 2009, 28, 3369−3380. (c) Hao, X.-Q.; Xu, Y.-X.; Yang,
M.-J.; Wang, L.; Niu, J.-L.; Gong, J.-F.; Song, M.-P. Organometallics
2012, 31, 835−846. (d) Hao, X.-Q.; Zhao, Y.-W.; Yang, J.-J.; Niu, J.-L.;
Gong, J.-F.; Song, M.-P. Organometallics 2014, 33, 1801−1811.
(e) Wang, T.; Niu, J.-L.; Liu, S.-L.; Huang, J.-J.; Gong, J.-F.; Song,
M.-P. Adv. Synth. Catal. 2013, 355, 927−937. (f) Hyodo, K.;
Nakamura, S.; Shibata, N. Angew. Chem., Int. Ed. 2012, 51, 10337−
10341. (g) Hyodo, K.; Nakamura, S.; Tsuji, K.; Ogawa, T.; Funahashi,
Y.; Shibata, N. Adv. Synth. Catal. 2011, 353, 3385−3390. (h) Hyodo,
K.; Kondo, M.; Funahashi, Y.; Nakamura, S. Chem. - Eur. J. 2013, 19,
4128−4134. (i) Nakamura, S.; Hyodo, K.; Nakamura, M.; Nakane, D.;
Masuda, H. Chem. - Eur. J. 2013, 19, 7304−7309. (j) Arai, T.;
Moribatake, T.; Masu, H. Chem. - Eur. J. 2015, 21, 10671−10675.
Catalytic Transfer Hydrogenation. A test tube was charged with
catalysts (0.005 mmol), NaOEt (0.025 mmol), and ketone 13 (0.5
mmol). After the addition of 2-propanol (5 mL) under an Ar
atmosphere, the reaction mixture was stirred at 80 °C for 24 h. After
removal of the solvent under reduced pressure, the residue was
purified by column chromatography on silica gel with hexane/ethyl
1
acetate (6:1). The ratio of products was calculated by H NMR. The
enantioselectivity of products was determined by using HPLC with a
proper chiral column.
ASSOCIATED CONTENT
■
S
* Supporting Information
(5) (a) Díez-Gonzal
109, 3612−3676. (b) Samojlowicz, C.; Bieniek, M.; Grela, K. Chem.
ar, V.; Bellemin-Laponnaz, S.;
́
ez, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009,
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00239.
Rev. 2009, 109, 3708−3742. (c) Ces
́
Gade, L. H. Chem. Soc. Rev. 2004, 33, 619−636. (d) Wang, F.; Liu, L.-
j.; Wang, W.; Li, S.; Shi, M. Coord. Chem. Rev. 2012, 256, 804−853.
CIF files for 5b, 5d, 8b and 9b (CIF)
́ ́
(6) Andrew, R. E.; Gonzalez-Sebastian, L.; Chaplin, A. B. Dalton
Trans. 2016, 45, 1299−1305.
NMR spectra (PDF)
(7) Grundemann, S.; Albrecht, M.; Loch, J. A.; Faller, J. W.; Crabtree,
̈
R. H. Organometallics 2001, 20, 5485−5488.
(8) Danopoulos, A. A.; Tulloch, A. A. D.; Winston, S.; Eastham, G.;
Hursthouse, M. B. Dalton Trans. 2003, 1009−1015.
AUTHOR INFORMATION
■
Corresponding Authors
(9) (a) Rubio, R. J.; Andavan, G. T. S.; Bauer, E. B.; Hollis, T. K.;
Cho, J.; Tham, F. S.; Donnadieu, B. J. Organomet. Chem. 2005, 690,
5353−5564. (b) Bauer, E. B.; Andavan, G. T. S.; Hollis, T. K.; Rubio,
R. J.; Cho, J.; Kuchenbeiser, G. R.; Helgert, T. R.; Letko, C. S.; Tham,
F. S. Org. Lett. 2008, 10, 1175−1178. (c) Zhang, X.; Wright, A. M.;
DeYonker, N. J.; Hollis, T. K.; Hammer, N. I.; Webster, C. E.; Valente,
*(J.I.) E-mail: jito@apchem.nagoya-u.ac.jp.
*(H.N.) E-mail: hnishi@apchem.nagoya-u.ac.jp.
Notes
The authors declare no competing financial interest.
I
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
E. J. Organometallics 2012, 31, 1664−1672. (d) Huckaba, A. J.; Cao,
B.; Hollis, T. K.; Valle, H. U.; Kelly, J. T.; Hammer, N. I.; Oliver, A. G.;
Webster, C. E. Dalton Trans. 2013, 42, 8820−8826. (e) Zhang, X.;
Cao, B.; Valente, E. J.; Hollis, T. K. Organometallics 2013, 32, 752−
761. (f) Reilly, S. W.; Box, H. K.; Kuchenbeiser, G. R.; Rubio, R. J.;
Letko, C. S.; Cousineau, K. D.; Hollis, T. K. Tetrahedron Lett. 2014, 55,
6738−6742.
(27) Nishibayashi, Y.; Segawa, K.; Ohe, K.; Uemura, S. Organo-
metallics 1995, 14, 5486−5487.
(28) (a) Sakanishi, K.; Ohira, M.; Mochida, I.; Okazaki, H.; Soeda, M.
Bull. Chem. Soc. Jpn. 1989, 62, 3994−4001. (b) Park, K. H.; Jang, K.;
Kim, H. J.; Son, S. U. Angew. Chem., Int. Ed. 2007, 46, 1152−1155.
(c) Pan, H.-B.; Wai, C. M. J. Phys. Chem. C 2009, 113, 19782−19782.
(29) (a) Borowski, A. F.; Vendier, L.; Sabo-Etienne, S.; Rozycka-
Sokolowska, E.; Gaudyn, A. V. Dalton Trans. 2012, 41, 14117−14125.
(b) Kuwano, R.; Morioka, R.; Kashiwabara, M.; Kameyama, N. Angew.
Chem., Int. Ed. 2012, 51, 4136−4139.
(10) (a) Raynal, M.; Cazin, C. S. J.; Vallee
Braunstein, P. Chem. Commun. 2008, 3983−3985. (b) Raynal, M.;
Pattacini, R.; Cazin, C. S. J.; Vallee, C.; Olivier-Bourbigou, H.;
́
, C.; Olivier-Bourbigou, H.;
́
(30) (a) Wang, D.; Astruc, D. Chem. Rev. 2015, 115, 6621−6686.
(b) Ito, J.; Nishiyama, H. Tetrahedron Lett. 2014, 55, 3133−3146.
(31) Appella, D. H.; Moritani, Y.; Shintani, R.; Ferreira, E. M.;
Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 9473−9474.
Braunstein, P. Organometallics 2009, 28, 4028−4047. (c) Chianese, A.
R.; Mo, A.; Lampland, N. L.; Swartz, R. L.; Bremer, P. T.
Organometallics 2010, 29, 3019−3026. (d) Schultz, K. M.; Goldberg,
K. I.; Gusev, D. G.; Heinekey, D. M. Organometallics 2011, 30, 1429−
1437. (e) Zuo, W.; Braunstein, P. Organometallics 2012, 31, 2606−
2615. (f) Chianese, A. R.; Shaner, S. E.; Tendler, J. A.; Pudalov, D. M.;
Shopov, D. Y.; Kim, D.; Rogers, S. L.; Mo, A. Organometallics 2012, 31,
7359−7367. (g) Jagenbrein, M.; Danopoulos, A. A.; Braunstein, P. J.
Organomet. Chem. 2015, 775, 169−172.
(11) (a) Zhang, Y.-M.; Shao, J.-Y.; Yao, C.-J.; Zhong, Y.-W. Dalton
Trans. 2012, 41, 9280−9282. (b) Naziruddin, A. R.; Huang, Z.-J.; Lai,
W.-C.; Lin, W.-J.; Hwang, W.-S. Dalton Trans. 2013, 42, 13161−
13171.
(12) Matson, E. M.; Martinez, G. E.; Ibrahim, A. D.; Jackson, B. J.;
Bertke, J. A.; Fout, A. R. Organometallics 2015, 34, 399−407.
(13) (a) Lv, K.; Cui, D. Organometallics 2008, 27, 5438−5440.
(b) Lv, K.; Cui, D. Organometallics 2010, 29, 2987−2993.
(14) Hahn, F. E.; Jahnke, M. C.; Pape, T. Organometallics 2007, 26,
150−154.
(15) (a) Fogler, E.; Balaraman, E.; Ben-David, Y.; Leitus, G.; Shimon,
L. J. W.; Milstein, D. Organometallics 2011, 30, 3826−3833.
(b) Balaraman, E.; Fogler, E.; Milstein, D. Chem. Commun. 2012,
́
48, 1111−1113. (c) del Pozo, C.; Corma, A.; Iglesias, M.; Sanchez, F.
Green Chem. 2011, 13, 2471−2481.
(16) Gade, L. H.; Bellemin-Laponnaz, S. Coord. Chem. Rev. 2007,
251, 718−725.
(17) (a) Rybtchinski, B.; Milstein, D. J. Am. Chem. Soc. 1999, 121,
4528−4528. (b) Gerisch, M.; Krumper, J. R.; Bergman, R. G.; Tilley,
T. D. J. Am. Chem. Soc. 2001, 123, 5818−5819. (c) Gerisch, M.;
Krumper, J. R.; Bergman, R. G.; Tilley, T. D. Organometallics 2003, 22,
47−58.
(18) van der Made, A. W.; van der Made, R. H. J. Org. Chem. 1993,
58, 1262−1263.
(19) Motoyama, Y.; Okano, M.; Narusawa, H.; Makihara, N.; Aoki,
K.; Nishiyama, H. Organometallics 2001, 20, 1580−1591.
(20) Wang, H. M. J.; Lin, I. J. B. Organometallics 1998, 17, 972−975.
(21) (a) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giardiello, M.;
Hilton, S. T.; Russell, D. R. Dalton Trans. 2003, 4132−4138.
(b) Ackermann, L. Chem. Rev. 2011, 111, 1315−1345.
(22) (a) Clear, J. M.; Kelly, J. M.; O’Connell, C. M.; Vos, J. G.;
Cardin, C. J.; Costa, S. R.; Edwards, A. J. J. Chem. Soc., Chem. Commun.
1980, 750−751. (b) Cole-Hamilton, D. J. J. Chem. Soc., Chem.
Commun. 1980, 1213−1215. (c) Forster, R. J.; Boyle, A.; Vos, J. G.;
Hage, R.; Dijkhuis, A. H. J.; de Graaff, R. A. G.; Haasnoot, J. G.; Prins,
R.; Reedijk, J. J. Chem. Soc., Dalton Trans. 1990, 121−126. (d) Serp, P.;
Hernandez, M.; Richard, B.; Kalck, P. Eur. J. Inorg. Chem. 2001, 2001,
2327−2336.
(23) Jafarpour, L.; Nolan, S. P. J. Organomet. Chem. 2001, 617−618,
17−27.
(24) (a) Andersson, P. G., Munslow, I. J., Eds. Modern Reduction
Methods; Wiley-VCH: Weinheim, Germany, 2008. (b) Cordova, A.,
́
Ed. Catalytic Asymmetric Conjugate Reactions; Wiley-VCH: Weinheim,
Germany, 2010.
(25) (a) Ikariya, T.; Blacker, A. J. Acc. Chem. Res. 2007, 40, 1300−
1308. (b) Yoshimura, M.; Tanaka, S.; Kitamura, M. Tetrahedron Lett.
2014, 55, 3635−3640.
(26) Ohkuma, T.; Doucet, H.; Pham, T.; Mikami, K.; Korenaga, T.;
Terada, M.; Noyori, R. J. Am. Chem. Soc. 1998, 120, 1086−1087.
J
DOI: 10.1021/acs.organomet.6b00239
Organometallics XXXX, XXX, XXX−XXX