Ruthenium-Catalyzed β-Alkylation of Secondary Alcohols and α-Alkylation of Ketones via Borrowing Hydrogen: Dramatic Influence of the Pendant N-Heterocycle

Article abstract of DOI:10.1021/acs.organomet.8b00847

Three bidentate ruthenium(II) complexes with a pyridonate fragment were prepared and fully characterized. These complexes are structurally similar, but differ in their pendant substituents. Complex 1 contains a phenyl unit, whereas complexes 2 and 3 have uncoordinated thienyl and thiazolyl groups, respectively. These complexes were tested as catalysts for β-alkylation of secondary alcohols with primary alcohols, and 3 shows the highest activity, suggesting the thiazolyl ring participates in the catalytic process. Furthermore, 3 is an excellent catalyst for α-alkylation of ketones with primary alcohols. Various α-alkylated ketones were synthesized in high yields, by using 0.05 mol % 3 and 0.25 equiv of t-BuOK within 30 min.

Full text of DOI:10.1021/acs.organomet.8b00847

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Ruthenium-Catalyzed β‑Alkylation of Secondary Alcohols and
α‑Alkylation of Ketones via Borrowing Hydrogen: Dramatic
Influence of the Pendant N‑Heterocycle
Chong Zhang,† Jiong-Peng Zhao,‡ Bowen Hu,† Jing Shi,† and Dafa Chen*,†
†MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemical Engineering
& Technology, Harbin Institute of Technology, Harbin 150001, PR China
‡School of Chemistry and Chemical Engineering, TKL of Organic Solar Cells and Photochemical Conversion, Tianjin University of
Technology, Tianjin 300384, PR China
S
* Supporting Information
ABSTRACT: Three bidentate ruthenium(II) complexes with a
pyridonate fragment were prepared and fully characterized. These
complexes are structurally similar, but differ in their pendant
substituents. Complex 1 contains a phenyl unit, whereas complexes
2 and 3 have uncoordinated thienyl and thiazolyl groups,
respectively. These complexes were tested as catalysts for β-
alkylation of secondary alcohols with primary alcohols, and 3 shows
the highest activity, suggesting the thiazolyl ring participates in the
catalytic process. Furthermore, 3 is an excellent catalyst for α-
alkylation of ketones with primary alcohols. Various α-alkylated
ketones were synthesized in high yields, by using 0.05 mol % 3 and
0.25 equiv of t-BuOK within 30 min.
Recently, our group reported ruthenium hydride complex C
(Figure 1, C), based on the NNN ligand with a 2-
hydroxypyridyl fragment, for β-alkylation of secondary alcohols
with primary alcohols.22 There is a pendant pyridyl group
existing in complex C. To investigate the influence of this
uncoordinated pyridyl group, and as a part of our interest in
developing bifunctional catalysts with a 2-hydroxypyridyl
moiety,23 herein we report the synthesis and catalytic activity
of three ruthenium pyridonate complexes (1−3). When used
as the catalyst for α-alkylation of ketones, complex 3 shows
TOF values up to 3680 h−1 (Figure 1, 3).
INTRODUCTION
■
Transition metal complexes with 2-hydroxypyridyl (2-HOPy)
derivatives are a group of metal−ligand bifunctional catalysts.1
2-Hydroxypyridyl is easily deprotonated to its pyridonate form
in the presence of a base, which can directly affect the first
coordination sphere of the metal and thus the catalytic activity.
Such complexes have been widely used for dehydrogenation,2
(transfer) hydrogenation,3 hydrofunctionalization,4 and bor-
rowing hydrogen reactions.5
The borrowing hydrogen methodology, also called hydrogen
autotransfer, has been developed rapidly in recent years,
because it is regarded as an environmentally friendly and an
atom-ecomonic tactic.5,6 For example, many β-alkylated
secondary alcohols and α-alkylated ketones were synthesized
by following this strategy, and H2O was the only by-
product.7−21 Direct β-alkylation of secondary alcohols with
primary alcohols has been applied under ruthenium,5d,7
iridium,8 palladium,9 copper,10 manganese,11 and cobalt12
catalysis or under transition metal-free conditions.13 Similarly,
various catalysts were also applicable for α-alkylation of
ketones with primary alcohols.5b,f,14−21 Currently, ruthenium
complex A containing 6,6′-dihydroxy-2,2′-bipyridine is the
most effective catalyst for β-alkylation of secondary alcohols,
which was reported by Kundu et al, showing TOFs up to 797.6
h−1 (Figure 1, A).5d While for α-alkylation of ketones, the most
active catalyst is an iridium N-heterocyclic carbene complex
RESULTS AND DISCUSSION
■
Synthesis and Characterization of Ru Complexes. To
explore if the pendant pyridyl group in complex C participates
in the catalytic cycle (Figure 1, C),22 we first replaced the
uncoordinated pyridyl of its ligand by a phenyl group, and
synthesized a ligand precursor [HO−C5H3N−C5H3N−CH2−
C6H5] (L1) (Scheme S1 in Supporting Information). Reaction
of L1 with RuHCl(PPh3)3(CO) in refluxing methanol
generated a yellow product, [(O−C5H3N−C5H3N−CH2−
C6H5)RuH(PPh3)2(CO)] (1) in 82% yield (Scheme 1).
The 1H NMR spectrum of 1 in CDCl3 at room temperature
exhibits six groups of signals between 7.52 and 6.02 ppm for
the pyridyl, phenyl, and PPh3 groups (41H), one singlet at 3.79
developed by Gu
̈
lcemal’s group, revealing TOF values up to
Received: November 18, 2018
970 h−1 (Figure 1, B).19a
© XXXX American Chemical Society
A
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Figure 1. Examples for β-alkylation of secondary alcohols and α-alkylation of ketones.
Scheme 1. Synthesis of Complexes 1−3
ppm for the −CH2− group (2H), and one triplet at −11.00
ppm for the Ru−H (1H). The 31P NMR shows one singlet for
the two PPh3 groups at 48.00 ppm. The IR displays one strong
absorption peak at 1945 cm−1 (in KBr) for the terminal CO.
The results indicate there are two trans-PPh3, one CO, one
hydride, and two pyridyl rings of ligand L1 coordinating with
Ru.
Two similar ligand precusors [HO−C5H3N−C5H3N−
CH2−C4H3S] (L2) and [HO-C5H3N−C5H3N−CH2−
C3H2NS] (L3) were also synthesized (Schemes S2 and S3),
Figure 2. Molecular structure of complex 2. The thermal ellipsoids
are displayed at 30% probability. Hydrogen atoms (except Ru−H),
and phenyl rings on PPh3 ligands have been omitted for clarity.
Selected bond distances (Å): Ru(1)−N(1), 2.186(3); Ru(1)−N(2),
2.195(3); Ru(1)−P(1), 2.3614(7); Ru(1)−H(1), 1.509(4); C(1)−
N(1), 1.382(4); C(5)−N(1), 1.361(5); C(1)−O(1), 1.251(5).
C(1)−C(2), 1.434(5); C(2)−C(3), 1.355(6); C(3)−C(4),
1.400(5); C(4)−C(5), 1.382(5).
and treated with RuHCl(PPh3)3(CO) in refluxing methanol.
Two bidentate ruthenium products [(O−C5H3N−C5H3N−
CH2−C4H3S)RuH(PPh3)2(CO)] (2) and [(O−C5H3N−
C5H3N−CH2−C3H2NS)RuH(PPh3)2(CO)] (3) were formed,
respectively (Scheme 1).
1
Each of the H NMR spectra of 2 and 3 in CDCl3 at room
temperature exhibits one singlet for the −CH2− group (3.90
ppm for 2; 4.37 ppm for 3), and one triplet for the Ru−H
group (−11.11 ppm for 2; −11.12 ppm for 3), similar to those
of complex 1. Their 31P chemical shifts in NMR spectra (47.20
ppm for 2; 47.93 ppm for 3) and CO absorption band in IR
spectra (1946 cm−1 for 2 and 1941 cm−1 for 3) are also
comparable to those of 1. These results suggest they have
similar structures.
Complexes 2 and 3 were further identified by X-ray
crystallography (Figure 2 and 3). The Ru ion in complex 2
is coordinated in an octahedral geometry. Ligand L2
coordinates with the Ru atom via its bipyridyl N atoms. The
CO ligand is trans to the pyridyl ring, and the hydride is trans
to the pyridonate group. The two PPh3 groups are in trans
positions. The C(1)−C(2) distance is 1.434(5) Å, obviously
longer than other C−C bonds in the same pyridonate ring,
suggesting it has some character as a single bond. The C(1)−
O(1) distance (1.251(5) Å) is in the range of a CO bond.3d
Similar to that of complex 2, the C(1)−C(2) bond in
complex 3 is 1.436(3) Å, also much longer than other C−C
bonds in the same heterocyclic ring, and the C(1)−O(1)
distance (1.259(3) Å) is also in the range of a CO bond,
suggesting the 2-hydroxypyridyl ring was converted to a
pyridonate. It is worth noting that the procedures for
synthesizing complexes 1−3 are similar to that for complex
C shown in Figure 1; however, their structures are different.
1−3 are neutral complexes with a pyridonate ring, while C is a
cationic complex with a 2-hydroxypyridyl group. The differ-
ence might be caused by the different basicity of the pendant
aromatic groups. The uncoordinated pyridyl group in C is
more basic than phenyl, thienyl, and thiazolyl rings; thus, it
might be easier to attract the HCl molecule, so that the ionic
form is more stable.
β-Alkylation of Secondary Alcohols with Primary
Alcohols. Initially, the coupling of 1-phenylethanol and benzyl
alcohol was selected as a model reaction to test the catalytic
activity of complexes 1−3. The reactions were conducted in
toluene at 110 °C for 60 min. Ruthenium complexes (0.5 mol
%) were used as the precatalysts and t-BuOK (0.5 equiv) as the
base under a N2 atmosphere, and the results are shown in
Table 1. It can be seen that the activity of complex 1 was much
B
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Subsequently, different bases were tested to optimize the
reaction conditions. The results are shown in Table 2. Weak
bases gave low conversion during the tested period (entries 1−
3). Strong bases such as KOH, NaOH, and t-BuOK
significantly increased the conversion, and t-BuOK was the
best (entries 4−6). To optimize the quantity of t-BuOK,
different amounts were also tested, and 0.5 equiv was optimal
(entries 6−10). The reaction could not occur in the absence of
a base or catalyst (entries 11 and 12). Thus, the optimized
reaction conditions were selected as entry 6 in Table 2, and β-
alkylation of 1-phenylethanol and its derivatives with a variety
of primary alcohols was then performed.
As shown in Table 3, a series of substrates are applicable.
When ortho-chlorobenzyl alcohol was used as the alkylation
reagent with 1-phenylethanol, the conversion and selectivity
were lower, compared with those of meta-chlorobenzyl alcohol.
It might be caused by a steric hindrance effect (entries 1 and
2). Other substituents in meta or/and para position(s) of
benzyl alcohol, either electron-withdrawing or -donating, do
not influence the reaction obviously, giving conversions
exceeding 90% with satisfied selectivity (entries 3−6). 2-
Hydroxymethylnaphthalene is also suitable for this reaction,
reaching a conversion of 95%, with a ratio of D/E as 98:2
(entry 7). An electron-withdrawing group, at the para position
of 1-phenylethanol, does not obviously influence the reaction,
while an electron-donating group, such as methoxyl group,
decreases the activity, especially the selectivity, dramatically
(entries 8 and 9). Cyclohexylmethanol and 1-butanol can also
react with 1-phenylethanol, generating corresponding products
in 80 and 81% yields, respectively, with satisfied selectivity
(entries 10 and 11).
α-Alkylation of Ketones with Primary Alcohols. α-
Alkylation of ketones has a similar mechanism as β-alkylation
of secondary alcohols with primary alcohols. We then tested
the catalytic activity of 3 for the reaction of acetophenone and
benzyl alcohol. The optimized condition was established as
following: 3 (0.05 mol %), t-BuOK (0.25 equiv), and 30 min in
refluxing toluene (Table 4). Nineteen alkylated ketones were
synthesized in the optimized condition, with isolated yields in
the range of 60−92%. Whether there is electron-withdrawing
or -donating group in benzyl alcohol, the corresponding
products could be isolated in high yields (entries 1−10).
Especially for para-methoxybenzyl alcohol, the product was
separated in 92% yield, with a TOF value as 3680 h−1 (entry
7). 2-Hydroxymethylnaphthalene also gave an isolated yield as
high as 91% (entry 11). Substituted acetophenones were also
explored, and except for 1-(4-fluorophenyl)-3-phenylpropan-1-
Figure 3. Molecular structure of complex 3. The thermal ellipsoids
are displayed at 30% probability. Hydrogen atoms (except Ru−H),
and phenyl rings on PPh3 ligands have been omitted for clarity.
Selected bond distances (Å): Ru(1)−N(1), 2.176(2); Ru(1)−N(2),
2.195(2); Ru(1)−P(1), 2.3643(5); Ru(1)−H, 1.60(4); C(1)−N(1),
1.381(3); C(5)−N(1), 1.360(3); C(1)−O(1), 1.259(3). C(1)−C(2),
1.436(3); C(2)−C(3), 1.362(4); C(3)−C(4), 1.401(4); C(4)−C(5),
1.380(3).
lower than that of complex C (entries 1 and 2), suggesting the
pyridyl ring of C plays a very important role. When complex 2
was used, the conversion was 62% within 60 min, comparable
to that of 1 (entry 3). Interestingly, complex 3 also exhibited as
high efficiency as C, reaching 95% conversion in 60 min (entry
4). These results indicate the pendant N-heterocycle rings
increase the catalytic activity dramatically, probably due to
their participation in the catalytic cycle with the substrates. In
fact, this phenomenon is not unusual, because several reactions
that the rates could be accelerated by pendant bases have been
reported.24 For example, Beller et al. found the hemilabile
pyridyl groups could accelerate the methoxycarbonylation of
olefins.24b Albrecht’s group developed an iridium complex with
a pendant pyridyl group, which could act as Lewis base for the
stabilization of substrates through hydrogen bonding during
oxidative coupling of benzylic amines.24c Bera and co-workers
synthesized a ruthenium complex for alcohol oxidation, and
the uncoordinated pyridyl of the naphthyridine played an
important role.24d
a
Table 1. β-Alkylation of 1-Phenylethanol with Benzyl Alcohol Using Ru Complexes C and 1−3
b
c
entry
catalyst
conversion
D/E ratio
d
1
C
1
2
3
94
61
62
95
95:5
2
3
4
83:17
89:11
95:5
a
Reaction conditions: catalyst (0.5 mol %), 1-phenylethanol (2.0 mmol), benzyl alcohol (2.0 mmol) and t-BuOK (1 mmol) in reflux condition in
b
c
d
toluene for 60 min under N2 atmosphere. Determined by GC analysis based on secondary alcohol. Determined by GC analysis. Data from ref
22.
C
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a
Table 2. β-Alkylation of 1-Phenylethanol with Benzyl Alcohol in the Presence of Different Bases
b
entry
base [equiv]
conversion [%]
1
2
3
4
5
6
7
8
Na2CO3 (0.5 equiv)
K2CO3 (0.5 equiv)
Cs2CO3 (0.5equiv)
KOH (0.5 equiv)
NaOH (0.5 equiv)
t-BuOK (0.5 equiv)
t-BuOK (0.4 equiv)
t-BuOK (0.3 equiv)
t-BuOK (0.2 equiv)
t-BuOK (0.1 equiv)
no base
4
4
8
74
60
95
81
74
62
46
0
9
10
11
c
12
t-BuOK (0.5 equiv)
0
a
Reaction conditions: catalyst 3 (0.5 mol %), 1-phenylethanol (2.0 mmol), benzyl alcohol (2.0 mmol), and base in reflux condition in toluene for
b
c
60 min under N2 atmosphere. Determined by GC analysis based on secondary alcohol. No catalyst.
one, other products were isolated in yields higher than 80%
(entries 12−15). Other aliphatic alcohols, such as 4-phenyl-1-
butanol, cyclohexylmethanol, and 1-butanol, gave correspond-
ing ketones in yields at 66−75% (entries 16−18). The
secondary alcohol, 1-phenylethanol, exhibits lower activity,
reaching a yield of 60% after 2 h (entry 19). To the best of our
knowledge, complex 3 is currently the best catalyst for α-
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were carried out
under an inert nitrogen atmosphere using a Schlenk line. Solvents
were distilled from appropriate drying agents under N2 before use. All
reagents were purchased from commercial sources. Liquid com-
pounds were degassed by standard freeze−pump−thaw procedures
prior to use. RuHCl(PPh3)3(CO),25 ethyl 6′-methoxy-[2,2′-bipyr-
idine]-6-carboxylate,23c 6-bromo-6′-methoxy-2,2′-bipyridine,26 and
benzylzinc bromide27 were prepared as previously described,
respectively. The 1H and 31P NMR spectra were recorded on a
alkylation of ketones, about 4 times as efficient as Gu
̈
lcemal’s
iridium complex.19a
Reaction Mechanisms. The proposed mechanism for β-
alkylation of secondary alcohols with primary alcohols
catalyzed by 3, is shown in Scheme 2. 3 first loses one
molecule of PPh3, to form active intermediate F with an open
site. Then, the primary and secondary alcohols are both
dehydrogenated to corresponding aldehyde and ketone,
respectively, releasing two molecules of H2, and one molecule
is absorbed by F, transformed to dihydride Ru(II) species G.
Cross-aldol condensation reaction then occurs between
aldehyde and ketone, generating an α,β-unsaturated ketone,
which then cooperates with G and H2 to form the final
product. The mechanism of α-alkylation of ketones is similar,
and the primary alcohol is needed to be oxidized to
corresponding aldehyde, with the released H2 accepted by F
to afford G. The difference is that in this step no extra H2 is
released.
1
Bruker Avance 400 spectrometer. The H NMR chemical shifts were
referenced to residual solvent as determined relative to Me4Si (δ = 0
ppm). The 31P{1H} chemical shifts were reported in ppm relative to
external 85% H3PO4. The 13C{1H} chemical shifts were reported in
ppm relative to the carbon resonance of CDCl3 (77.0 ppm).
Elemental analyses were performed on a PerkinElmer 240C analyzer.
The high-resolution mass spectrum (HR-MS) was recorded on a
Varian 7.0 T FTICR-MS by the ESI technique. IR spectra were
recorded on a Nicolet iS5 FT-IR spectrometer. X-ray diffraction
studies were carried out in a SuperNova X-ray single crystal
diffractometer or a Bruker D8 Quest X-ray diffractometer. Data
collections were performed using four-circle kappa diffractometers
equipped with CCD detectors. Data were reduced and then corrected
for absorption. Solution, refinement, and geometrical calculations for
all crystal structures were performed by SHELXTL. All of the GC
measurements were performed on Agilent GC7890A equipment using
an Agilent 19091B-102 (25 m, 220 μm) column.
Synthesis of 6-Benzyl-6′-methoxy-2,2′-bipyridine. Pd-
(PPh3)4 (0.46 g, 0.40 mmol) and 6-bromo-6′-methoxy-2,2′-bipyridine
(2.12 g, 8.00 mmol) were added into benzylzinc bromide (1.98 g,
8.40 mmol) in THF at refluxing overnight. The crude product was
purified by column chromatography on silica gel to give the product
as a white solid (0.91 g, 41%). Mp: 118 °C. HRMS for C18H16N2O +
CONCLUSIONS
■
In summary, three bidentate bifunctional ruthenium com-
plexes, 1−3, with a pridonate fragment were synthesized.
These complexes were tested as catalysts for β-alkylation of
secondary alcohols, by using primary alcohols as alkylated
reagents. Complex 3 with a pendant thiazolyl group shows
highest activity, suggesting the uncoordinated N-heterocycle
interacts with the substrates in the catalytic cycle, which is
important for designing new catalysts for such kind of reaction.
Complex 3 was further treated as catalyst for α-alkylation of
ketones with primary alcohols, revealing exceptionally high
TOF values (up to 3680 h−1). To the best of our knowledge, it
is the most active catalyst for such transformation reported up
to date.
1
H, 277.1341. Found, 277.1343. H NMR (400 MHz, CDCl3, ppm):
8.23 (d, J = 8.0 Hz, 1H), 8.10 (d, J = 7.6 Hz, 1H), 7.72−7.67 (m,
2H), 7.35−7.30 (m, 4H), 7.25−7.21 (m, 1H), 7.08 (d, J = 7.6 Hz,
1H), 6.77 (d, J = 8.0 Hz, 1H). 4.25 (s, 2H), 4.04 (s, 3H). 13C NMR
(100 MHz, CDCl3): 163.4, 160.2, 155.5, 153.7, 139.7, 139.4, 137.1,
129.2, 128.5, 126.3, 122.9, 118.4, 113.9, 110.9, 99.9, 53.1, 44.8.
Synthesis of L1: 6′-Benzyl-[2,2′-bipyridin]-6-ol. A solution of
6-benzyl-6′-methoxy-2,2′-bipyridine (0.50 g, 1.81 mmol) in 8 mL of
HBr (40% in water) was heated at reflux for 3 h. After cooling to
room temperature, the yellow solution was neutralized by slow
addition of a saturated aqueous solution of NaOH. The aqueous
D
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a
Table 3. β-Alkylation of 1-Phenylethanol and Benzyl Alcohol with Diverse Substitutions
a
Reaction conditions: catalyst 3 (0.5 mol %), 1-phenylethanol (2.0 mmol), benzyl alcohol (2.0 mmol), and t-BuOK (1 mmol) under reflux
b
c
condition in toluene for 60 min under N2 atmosphere. Determined by GC analysis based on secondary alcohol. Determined by GC analysis.
E
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a
Table 4. Scope of α-Alkylation of Ketones with Primary Alcohols Catalyzed by Complex 3
a
Reaction conditions: catalyst 3 (0.05 mol %), ketone (1.0 mmol), primary alcohol (1.0 mmol), and t-BuOK (0.25 mmol) under reflux condition
b
c
in toluene for 30 min under N2 atmosphere. Isolated yields. Using 2 h of reflux.
solution was extracted with CH2Cl2. The combined organic extracts
were dried over Na2SO4, filtered, and concentrated to afford the
product as a pale yellow solid (0.4 g, 85%). Mp: 146 °C. HRMS for
added. The mixture was further stirred at −20 °C for 2.5 h. The
solution was quenched with dilute HCl (1.0 M) and then neutralized
with a solution of NaOH. The mixture was extracted with ethyl
acetate, and the solvent was concentrated. The crude product was
purified by column chromatography on silica gel (petroleum ether/
ethyl acetate, v/v = 10:1) to give the product as a white solid (0.75 g,
66%). Mp: 100 °C. HRMS for C16H12N2O2S + H, 297.0698. Found,
1
C17H14N2O + H, 263.1184. Found, 263.1186. H NMR (400 MHz,
CDCl3, ppm): 10.75 (s, 1H), 7.72−7.63 (m, 2H), 7.50−7.46 (m,
1H), 7.34−7.28 (m, 4H), 7.24−7.22 (m, 1H), 7.16 (d, J = 7.2 Hz,
1H), 6.79 (d, J = 6.8 Hz, 1H), 6.64 (d, J = 8.8 Hz, 1H), 4.19 (s, 2H).
13C NMR (100 MHz, CDCl3): 162.7, 161.0, 147.1, 141.8, 140.6,
1
297.0699. H NMR (400 MHz, CDCl3, ppm): 8.64 (d, J = 8.0 Hz,
1H), 8.42 (d, J = 4.0 Hz, 1H), 8.25 (d, J = 7.6 Hz, 1H), 8.21 (d, J =
7.6 Hz, 1H), 8.00 (t, J = 8.0 Hz, 1H), 7.81−7.77 (m, 2H), 7.23 (t, J =
4.4 Hz, 1H), 6.84 (d, J = 8.0 Hz, 1H), 4.08 (s, 3H). 13C NMR (100
MHz, CDCl3): 183.3, 163.6, 155.4, 153.2, 152.7, 139.6, 138.9, 138.0,
136.6, 136.5, 127.4, 124.2, 123.6, 114.6, 111.7, 53.3.
138.7, 137.9, 129.1, 128.8, 126.7, 124.1, 122.0, 117.3, 102.8, 44.5,
29.7.
Synthesis of (6′-Methoxy-[2,2′-bipyridin]-6-yl)(thiophen-2-
yl)methanone. Thiophene (0.32 g, 3.85 mmol) in 15 mL of THF
was added drop by drop to a solution of n-BuLi (1.60 mL, 2.4 M, 3.85
mmol) at −78 °C. After 60 min of stirring at −78 °C, ethyl 6′-
methoxy-[2,2′-bipyridine]-6-carboxylate (1.0 g, 3.85 mmol) was
Synthesis of 6-Methoxy-6′-(thiophen-2-ylmethyl)-2,2′-bi-
pyridine. To a solution of (6′-methoxy-[2,2′-bipyridin]-6-yl)-
F
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Scheme 2. Proposed Reaction Mechanism
(thiophen-2-yl)methanone (0.5 g, 1.69 mmol) in 10 mL of ethylene
glycol was added NaOH (0.75 g) and NH2NH2 (10.0 mL, 80% in
water). The mixture was heated at 100 °C for 5 h. Water (10 mL) was
added and the solution was neutralized by dilute HCl (1.0 M) and
extracted with ethyl acetate. The organic phase was dried over
Na2SO4 and evaporated under vacuum. The crude product was
purified by column chromatography on silica gel (petroleum ether/
ethyl acetate, v/v = 20:1) to give the product as a white solid (0.3 g,
63%). Mp: 80 °C. HRMS for C16H14N2OS + H, 283.0905. Found,
with a solution of NaOH. The mixture was extracted with ethyl
acetate, and the solvent was concentrated. The crude product was
purified by column chromatography on silica gel (petroleum ether/
ethyl acetate, v/v = 1:1) to give the product as a yellow solid (0.80 g,
70%). Mp: 120 °C. HRMS for C15H11N3O2S + H, 298.0650. Found,
1
298.0655. H NMR (400 MHz, CDCl3, ppm): 8.69 (d, J = 3.6 Hz,
1H), 8.33 (d, J = 7.6 Hz, 1H), 8.24−8.21 (m, 2H), 8.05 (t, J = 7.6 Hz,
1H), 7.83 (d, J = 3.2 Hz, 1H), 7.79 (t, J = 7.6 Hz, 1H), 6.85 (d, J = 8.0
Hz, 1H), 4.07 (s, 3H). 13C NMR (100 MHz, CDCl3): 180.7, 163.7,
159.7, 155.8, 152.3, 151.9, 144.8, 139.6, 138.2, 127.6, 125.1, 124.3,
114.8, 111.9, 53.4.
1
283.0908. H NMR (400 MHz, CDCl3, ppm): 8.26 (d, J = 7.6 Hz,
1H), 8.14 (d, J = 7.6 Hz, 1H), 7.72 (q, J = 7.6 Hz, 2H), 7.20−7.18
(m, 2H), 6.97−6.95 (m, 2H), 6.78 (d, J = 8.4 Hz, 1H), 4.43 (s, 2H),
4.04 (s, 3H). 13C NMR (100 MHz, CDCl3): 162.4, 158.1, 154.5,
152.5, 140.8, 138.3, 136.3, 125.7, 124.6, 123.4, 121.4, 117.6, 112.9,
109.9, 52.1, 37.8.
Synthesis of 2-((6′-Methoxy-[2,2′-bipyridin]-6-yl)methyl)-
thiazole. To a solution of (6′-methoxy-[2,2′-bipyridin]-6-yl)-
(thiazol-2-yl)methanone (0.5 g, 1.68 mmol) in 10 mL of ethylene
glycol was added NaOH (0.75 g) and NH2NH2 (10.0 mL, 80% in
water). The mixture was heated at 100 °C for 5 h. Water (10 mL) was
added, and the solution was neutralized by dilute HCl (1.0 M) and
extracted with ethyl acetate. The organic phase was dried over
Na2SO4 and evaporated under vacuum. The crude product was
purified by column chromatography on silica gel (petroleum ether/
ethyl acetate, v/v = 2:1) to give the product as an orange oil liquid
(0.35 g, 74%). HRMS for C15H13N3OS + H, 284.0858. Found,
Synthesis of L2: 6′-(Thiophen-2-ylmethyl)-[2,2′-bipyridin]-6-
ol. A solution of 6-methoxy-6′-(thiophen-2-ylmethyl)-2,2′-bipyridine
(0.30 g, 1.06 mmol) in 5 mL of HBr (40% in water) was heated at
reflux for 3 h. After cooling to room temperature, the brown solution
was neutralized by slow addition of a saturated aqueous solution of
NaOH. The aqueous solution was extracted with CH2Cl2. The
combined organic extracts were dried over Na2SO4, filtered, and
concentrated to afford the product as a yellow solid (0.25 g, 89%).
Mp: 138 °C. HRMS for C15H12N2OS + H, 269.0749. Found,
1
284.0860. H NMR (400 MHz, CDCl3, ppm): 8.32 (d, J = 7.6 Hz,
1H), 8.14 (d, J = 7.6 Hz, 1H), 7.78−7.70 (m, 3H), 7.30 (d, J = 7.6
Hz, 1H), 7.26 (d, J = 3.2 Hz, 1H), 6.79 (d, J = 8.0 Hz, 1H), 4.63 (s,
2H), 4.06 (s, 3H). 13C NMR (100 MHz, CDCl3): 168.0, 163.5, 156.6,
155.9, 153.3, 142.1, 139.3, 137.5, 123.0, 119.5, 119.2, 114.0, 110.9,
53.1, 42.1.
1
269.0753. H NMR (400 MHz, CDCl3, ppm): 11.05 (s, 1H), 7.77−
7.68 (m, 2H), 7.56−7.52 (m, 1H), 7.28 (s, 1H), 7.20 (dd, J = 5.2, 1.2
Hz, 1H), 6.97−6.87 (m, 3H), 6.69 (d, J = 9.2 Hz, 1H), 4.40 (s, 2H).
13C NMR (100 MHz, CDCl3): 161.9, 158.9, 146.2, 140.7, 139.7,
Synthesis of L3: 6′-(Thiazol-2-ylmethyl)-[2,2′-bipyridin]-6-
ol. A solution of 2-((6′-methoxy-[2,2′-bipyridin]-6-yl)methyl)-
thiazole (0.30 g, 1.06 mmol) in 5 mL of HBr (40% in water) was
heated at reflux for 3 h. After cooling to room temperature, the brown
solution was neutralized by slow addition of a saturated aqueous
solution of NaOH. The aqueous solution was extracted with CH2Cl2.
The combined organic extracts were dried over Na2SO4, filtered, and
concentrated to afford the product as a brown solid (0.24 g, 86%).
139.5, 137.1, 126.0, 125.0, 123.8, 122.7, 121.0, 116.6, 102.1, 37.5.
Synthesis of (6′-Methoxy-[2,2′-bipyridin]-6-yl)(thiazol-2-yl)-
methanone. 2-Bromothiazole (0.63 g, 3.85 mmol) in 15 mL THF
was added drop by drop to a solution of n-BuLi (1.60 mL, 2.4 M, 3.85
mmol) at −78 °C. After 60 min of stirring at −78 °C, ethyl 6′-
methoxy-[2,2′-bipyridine]-6-carboxylate (1.0 g, 3.85 mmol) was
added. The mixture was further stirred at −20 °C for 2.5 h. The
solution was quenched with dilute HCl (1.0 M) and then neutralized
G
DOI: 10.1021/acs.organomet.8b00847
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Mp: 135 °C. HRMS for C14H11N3OS + H, 270.0701. Found,
alcohol reaction was carried out in a 10 mL Schlenk tube under
nitrogen conditions. Initially, catalyst 3 (0.5 mol %) and t-BuOK (0.5
equiv) were taken as solid, and then under nitrogen conditions,
secondary alcohol (1 equiv), primary alcohol (1 equiv), and toluene
(3 mL) were added and the resulting mixture heated at 110 °C (oil
bath temperature) for 60 min. After cooling to room temperature, the
toluene was evaporated under reduced pressure, and the resulting
mixture was purified by silica gel column chromatography using ethyl
acetate and hexane as eluent to afford the desire product.
General Procedure for the α-Alkylation of Ketones with
Primary Alcohols to Give α-Alkylated Ketones. To a 10 mL
Schlenk tube were added ketone (1 equiv), primary alcohol (1 equiv),
catalyst 3 (0.05 mol %), and t-BuOK (0.25 equiv) in toluene (3 mL)
under a nitrogen atmosphere. The reaction mixture was stirred at 130
°C (oil bath temperature) for 30 min. After the reaction was
completed, the reaction mixture was evaporated and the residue was
purified by TLC on silica gel plates using EA/PE as eluent to afford
the corresponding ketone product.
1
270.0702. H NMR (400 MHz, CDCl3, ppm): 10.69 (s, 1H), 7.81−
7.71 (m, 3H), 7.49 (t, J = 8.0 Hz, 1H), 7.39 (d, J = 7.6 Hz, 1H), 7.28
(d, J = 3.2 Hz, 1H), 6.81 (d, J = 6.8 Hz, 1H), 6.64 (d, J = 9.2 Hz, 1H),
4.59 (s, 2H). 13C NMR (100 MHz, CDCl3): 166.5, 162.7, 157.3,
147.5, 142.6, 141.5, 140.5, 138.3, 124.3, 122.3, 119.6, 118.0, 103.0,
41.7.
Synthesis of 1. A solution of L1 (0.17 g, 0.63 mmol) and
RuHCl(PPh3)3(CO) (0.58 g, 0.63 mmol) was heated in refluxing
methanol (200 mL) for 24 h. The mixture was allowed to cool to
room temperature, and the organic phase was evaporated under
vacuum. The crude product was recrystallized with dichloromethane/
n-hexane to give 1 as a yellow powder (0.48 g, 82%). Single crystals
suitable for X-ray crystallographic determination were grown with
CH2Cl2/CH3OH/n-hexane at ambient temperature. Mp: 145 °C.
Anal. Calcd for C54H44N2P2O2Ru: C, 70.81; H, 4.84; N, 3.06. Found:
C, 70.92; H, 4.82; N, 3.00. IR (νCO, KBr, cm−1): 1945 (s). IR (νRu−H
,
KBr, cm−1): 1911 (s). 1H NMR (500 MHz, CDCl3, ppm, r.t.): 7.52−
7.49 (m, 13H), 7.33 (br s, 1H), 7.29−7.28 (m, 4H), 7.21−7.13 (m,
17H), 6.90 (br s, 1H), 6.36−6.31 (m, 2H), 6.05−6.02 (m, 3H), 3.79
1,3-Diphenylpropan-1-ol.5d 1H NMR (400 MHz, CDCl3, ppm):
7.35−7.18 (m, 10H), 4.68 (t, J = 7.2 Hz, 1H), 2.78−2.62 (m, 2H),
2.17−1.98 (m, 2H), 1.86 (s, 1H).
1
(s, 2H), −11.00 (t, J = 19.5 Hz, 1H). H NMR (400 MHz, CDCl3,
3-(2-Chlorophenyl)-1-phenylpropan-1-ol.5d 1H NMR (400 MHz,
CDCl3, ppm): 7.38−7.10 (m, 9H), 4.72 (dd, J = 7.6, 5.2 Hz, 1H),
2.93−2.73 (m, 2H), 2.14−1.99 (m, 2H), 1.89 (s, 1H).
3-(3-Chlorophenyl)-1-phenylpropan-1-ol.5d 1H NMR (400 MHz,
CDCl3, ppm): 7.37−7.14 (m, 8H), 7.07−7.05 (m, 1H), 4.66 (dd, J =
7.6, 5.2 Hz, 1H), 2.76−2.60 (m, 2H), 2.14−1.95 (m, 2H), 1.92 (s,
1H).
ppm, −50 °C): 8.11 (s, 1H), 7.52−7.28 (m, 16H), 7.24−7.09 (m,
18H), 6.90 (t, J = 7.6 Hz, 1H), 6.42 (d, J = 8.4 Hz, 1H), 6.28 (d, J =
7.2 Hz, 1H), 5.96 (d, J = 8.0 Hz, 1H), 5.81 (d, J = 7.2 Hz, 2H), 3.60
(s, 2H), −10.87 (t, J = 19.6 Hz, 1H). 31P NMR (162 MHz, CDCl3,
ppm): 48.00. 13C NMR (100 MHz, CDCl3): 206.0 (CO), 163.7,
151.7, 137.6, 136.1, 134.7, 134.5, 134.0, 133.9, 133.9, 133.8, 133.8,
133.7, 133.5, 133.3, 133.1, 130.1, 129.9, 129.3, 129.1, 128.5, 128.4,
128.0, 127.9, 127.8, 126.6, 122.9, 119.5, 105.8, 65.9, 53.5, 50.6, 49.3
(CH2).
3-(4-Bromophenyl)-1-phenylpropan-1-ol.5d 1H NMR (400 MHz,
CDCl3, ppm): 7.39−7.24 (m, 7H), 7.04 (d, J = 8 Hz, 2H), 4.64 (dd, J
= 7.6, 5.2 Hz, 1H), 2.72−2.57 (m, 2H), 2.13−1.92 (m, 3H).
3-(4-Fluorophenyl)-1-phenylpropan-1-ol.5d 1H NMR (400 MHz,
CDCl3, ppm): 7.37−7.24 (m, 5H), 7.15−7.10 (m, 2H), 6.98−6.92
(m, 2H), 4.65 (dd, J = 8.0, 5.6 Hz, 1H), 2.75−2.59 (m, 2H), 2.14−
1.95 (m, 2H), 1.91 (s, 1H).
Synthesis of 2. A solution of L2 (0.17 g, 0.63 mmol) and
RuHCl(PPh3)3(CO) (0.58 g, 0.63 mmol) was heated in refluxing
methanol (200 mL) for 24 h. The mixture was allowed to cool to
room temperature, and the organic phase was evaporated under
vacuum. The crude product was recrystallized with dichloromethane/
n-hexane to give 2 as a yellow powder (0.48 g, 83%). Single crystals
suitable for X-ray crystallographic determination were grown with
CH2Cl2/CH3OH/n-hexane at ambient temperature. Mp: 220 °C.
Anal. Calcd for C52H42N2O2P2RuS: C, 67.74; H, 4.59; N, 3.04.
Found: C, 67.45; H, 4.62; N, 2.97. IR (νCO, KBr, cm−1): 1946 (s). IR
3-(4-Methoxyphenyl)-1-phenylpropan-1-ol.5d 1H NMR (400
MHz, CDCl3, ppm): 7.35−7.26 (m, 5H), 7.11 (d, J = 8.8 Hz, 2H),
6.82 (d, J = 8.4 Hz, 2H), 4.67 (dd, J = 7.6, 5.6 Hz, 1H), 3.78 (s, 3H),
2.73−2.57 (m, 2H), 2.15−1.95 (m, 2H), 1.86 (s, 1H).
3-(3,4-Dimethoxyphenyl)-1-phenylpropan-1-ol.28 1H NMR (400
MHz, CDCl3, ppm): 7.38−7.25 (m, 5H), 6.79−6.70 (m, 3H), 4.68
(dd, J = 7.6, 5.2 Hz, 1H), 3.85 (s, 6H), 2.74−2.58 (m, 2H), 2.16−
1.96 (m, 2H), 1.90 (s, 1H).
1
(νRu−H, KBr, cm−1): 1912 (s). H NMR (500 MHz, CDCl3, ppm):
7.49 (br s, 13H), 7.37−7.36 (m, 2H), 7.28−7.27 (m, 5H), 7.21−7.18
(m, 13H), 7.12 (d, J = 5.0 Hz, 1H), 6.90−6.85 (m, 1H), 6.34 (d, J =
5.5 Hz, 2H), 6.19 (d, J = 7.0 Hz, 1H), 5.92 (s, 1H), 3.90 (s, 2H),
3-(Naphthalen-2-yl)-1-phenylpropan-1-ol.29 1H NMR (400
MHz, CDCl3, ppm): 7.80−7.75 (m, 3H), 7.62 (s, 1H), 7.46−7.39
(m, 2H), 7.36−7.23 (m, 6H), 4.70 (dd, J = 8.0, 5.6 Hz, 1H), 2.94−
2.79 (m, 2H), 2.26−2.06 (m, 2H), 1.89 (s, 1H).
1
−11.11 (t, J = 20 Hz, 1H). H NMR (400 MHz, CDCl3, ppm, −50
°C): 8.12 (s, 1H), 7.55−7.28 (m, 17H), 7.20−7.11 (m, 15H), 6.92 (t,
J = 7.6 Hz, 1H), 6.83 (t, J = 3.6 Hz, 1H), 6.42 (d, J = 8.4 Hz, 1H),
6.32 (d, J = 7.2 Hz, 1H), 6.13 (d, J = 6.8 Hz, 1H), 5.73 (d, J = 2.4 Hz,
1H), 3.71 (s, 2H), −10.97 (t, J = 20.0 Hz, 1H). 31P NMR (162 MHz,
CDCl3, ppm): 47.20.
1-(4-Chlorophenyl)-3-phenylpropan-1-ol.5d 1H NMR (400 MHz,
CDCl3, ppm): 7.36−7.25 (m, 6H), 7.21−7.17 (m, 3H), 4.66 (dd, J =
7.6, 5.2 Hz, 1H), 2.76−2.62 (m, 2H), 2.14−1.94 (m, 2H), 1.86 (s,
1H).
Synthesis of 3. A solution of L3 (0.17 g, 0.63 mmol) and
RuHCl(PPh3)3(CO) (0.58 g, 0.63 mmol) was heated in refluxing
methanol (200 mL) for 24 h. The mixture was allowed to cool to
room temperature, and the organic phase was evaporated under
vacuum. The crude product was recrystallized with dichloromethane/
n-hexane to give 3 as a yellow powder (0.48 g, 83%). Single crystals
suitable for X-ray crystallographic determination were grown with
CH2Cl2/CH3OH/n-hexane at ambient temperature. Mp: 180 °C.
Anal. Calcd for C51H41N3O2P2RuS: C, 66.37; H, 4.48; N, 4.55.
Found: C, 66.61; H, 4.51; N, 4.56. IR (νCO, KBr, cm−1): 1941 (s). 1H
NMR (500 MHz, CDCl3, ppm): 7.61 (d, J = 3.0 Hz, 1H), 7.56−7.52
(m, 12H), 7.28−7.23 (m, 8H), 7.19−7.16 (m, 12H), 7.11 (d, J = 3.0
Hz, 1H), 6.91 (t, J = 7.0 Hz, 1H), 6.37 (s, 2H), 6.25 (d, J = 6.0 Hz,
1H), 4.37 (s, 2H), −11.19 (t, J = 19.5 Hz, 1H). 1H NMR (400 MHz,
CDCl3, ppm, −50 °C): 7.60−7.30 (m, 15H), 7.26−6.89 (m, 20H),
6.43 (d, J = 8.4 Hz, 1H), 6.32 (d, J = 6.4 Hz, 1H), 6.22 (d, J = 6.8 Hz,
1H), 4.22 (s, 2H), −11.05 (t, J = 19.6 Hz, 1H). 31P NMR (162 MHz,
CDCl3, ppm): 47.93.
1-(4-Methoxyphenyl)-3-phenylpropan-1-ol.5d 1H NMR (400
MHz, CDCl3, ppm): 7.28−7.23 (m, 4H), 7.18−7.15 (m, 3H),
6.89−6.85 (m, 2H), 4.60 (dd, J = 7.6, 6.0 Hz, 1H), 3.78 (s, 3H),
2.74−2.58 (m, 2H), 2.16−1.94 (m, 3H).
3-Cyclohexyl-1-phenylpropan-1-ol.5d 1H NMR (500 MHz,
CDCl3, ppm): 7.36−7.27 (m, 5H), 4.63 (t, J = 6.5 Hz, 1H), 1.84−
1.61 (m, 8H), 1.36−1.29 (m, 1H), 1.26−1.10 (m, 5H), 0.89−0.82
(m, 2H).
1-Phenylhexan-1-ol.5d 1H NMR (500 MHz, CDCl3, ppm): 7.35−
7.25 (m, 5H), 4.64 (t, J = 7.0 Hz, 1H), 1.89 (s, 1H), 1.82−1.75 (m,
1H), 1.72−1.66 (m, 1H), 1.46−1.36 (m, 1H), 1.32−1.23 (m, 5H),
0.88−0.85 (m, 3H).
1,3-Diphenylpropan-1-one.14a 1H NMR (400 MHz, CDCl3,
ppm): 7.97−7.95 (m, 2H), 7.57−7.54 (m, 1H), 7.45 (t, J = 7.6 Hz,
2H), 7.32−7.19 (m, 5H), 3.31 (t, J = 7.2 Hz, 2H), 3.07 (t, J = 8.0 Hz,
2H).
3-(2-Chlorophenyl)-1-phenylpropan-1-one.19a 1H NMR (400
MHz, CDCl3, ppm): 7.99 (d, J = 7.6 Hz, 2H), 7.57 (t, J = 7.2 Hz,
General Procedure for β-Alkylation of Secondary Alcohols
with Primary Alcohols. The catalytic β-alkylation of secondary
H
DOI: 10.1021/acs.organomet.8b00847
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1H), 7.47 (t, J = 7.6 Hz, 2H), 7.39−7.33 (m, 2H), 7.23−7.16 (m,
2H), 3.34 (t, J = 7.2 Hz, 2H), 3.20 (t, J = 7.6 Hz, 2H).
3-(3-Chlorophenyl)-1-phenylpropan-1-one.30 1H NMR (400
MHz, CDCl3, ppm): 7.96 (d, J = 7.6 Hz, 2H), 7.57 (t, J = 7.2 Hz,
1H), 7.46 (t, J = 8.0 Hz, 2H), 7.26−7.13 (m, 4H), 3.30 (t, J = 7.6 Hz,
2H), 3.05 (t, J = 7.6 Hz, 2H).
7.32−7.23 (m, 4H), 7.21−7.15 (m, 1H), 3.56−3.44 (m, 1H), 3.33−
3.15 (m, 2H), 1.34 (d, J = 6.8 Hz, 3H).
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00847.
3-(4-Chlorophenyl)-1-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.96 (d, J = 7.2 Hz, 2H), 7.57 (t, J = 7.2 Hz,
1H), 7.47 (t, J = 8.0 Hz, 2H), 7.28−7.26 (m, 2H), 7.21−7.19 (m,
2H), 3.30 (t, J = 7.2 Hz, 2H), 3.06 (t, J = 7.6 Hz, 2H).
3-(4-Fluorophenyl)-1-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.95 (d, J = 8.8 Hz, 2H), 7.56 (t, J = 8.4 Hz,
1H), 7.46 (t, J = 7.6 Hz, 2H), 7.23−7.19 (m, 2H), 6.98 (t, J = 8.8 Hz,
2H), 3.29 (t, J = 7.2 Hz, 2H), 3.05 (t, J = 7.6 Hz, 2H).
1-Phenyl-3-(m-tolyl)propan-1-one.14a 1H NMR (400 MHz,
CDCl3, ppm): 7.98 (d, J = 8.0 Hz, 2H), 7.57 (t, J = 7.2 Hz, 1H),
7.47 (t, J = 7.6 Hz, 2H), 7.21 (t, J = 7.6 Hz, 1H), 7.09−7.03 (m, 3H),
3.31 (t, J = 7.6 Hz, 2H), 3.05 (t, J = 8.0 Hz, 2H), 2.35 (s, 3H).
3-(4-Methoxyphenyl)-1-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.96 (d, J = 7.2 Hz, 2H), 7.56 (t, J = 7.6 Hz,
1H), 7.45 (t, J = 8.0 Hz, 2H), 7.17 (d, J = 8.4 Hz, 2H), 6.84 (d, J = 8.4
Hz, 2H), 3.79 (s, 3H), 3.28 (t, J = 7.2 Hz, 2H), 3.02 (t, J = 8.0 Hz,
2H).
Crystallographic details for complexes 2 and 3, screening
reactions, synthetic routes of complexes 1−3, and IR
and NMR spectra of the new compounds (PDF)
Accession Codes
CCDC 1879634−1879635 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*E-mail: dafachen@hit.edu.cn.
■
3-(4-Bromophenyl)-1-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.96−7.94 (m, 2H), 7.57 (t, J = 7.2 Hz, 1H),
7.48−7.40 (m, 4H), 7.13 (d, J = 8.0 Hz, 2H), 3.28 (t, J = 7.2 Hz, 2H),
3.03 (t, J = 7.6 Hz, 2H).
ORCID
3-(3-Methoxyphenyl)-1-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.97−7.95 (m, 2H), 7.55 (t, J = 7.2 Hz, 1H),
7.45 (t, J = 8.0 Hz, 2H), 7.25−7.20 (m, 1H), 6.85−6.74 (m, 3H),
3.79 (s, 3H), 3.30 (t, J = 7.6 Hz, 2H), 3.05 (t, J = 8.0 Hz, 2H).
3-(3,4-Dimethoxyphenyl)-1-phenylpropan-1-one.14a 1H NMR
(400 MHz, CDCl3, ppm): 7.97−7.95 (m, 2H), 7.56 (t, J = 7.6 Hz,
1H), 7.45 (t, J = 7.6 Hz, 2H), 6.82−6.78 (m, 3H), 3.86 (d, J = 4.8 Hz,
6H), 3.29 (t, J = 7.2 Hz, 2H), 3.02 (t, J = 8.0 Hz, 2H).
3-(Naphthalen-2-yl)-1-phenylpropan-1-one.31 1H NMR (400
MHz, CDCl3, ppm): 7.99−7.97 (m, 2H), 7.82−7.78 (m, 3H), 7.70
(s, 1H), 7.56 (t, J = 7.6 Hz, 1H), 7.48−7.39 (m, 5H), 3.40 (t, J = 7.2
Hz, 2H), 3.24 (t, J = 8.0 Hz, 2H).
Jiong-Peng Zhao: 0000-0003-1512-0171
Bowen Hu: 0000-0001-9815-8938
Dafa Chen: 0000-0002-7650-4024
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (Nos. 21672045, 21871068 and
21871209), the National Science and Technology Pillar
Program during the Twelfth Five-Year Plan Period
(2015BAD15B0502), the China Postdoctoral Science Founda-
tion (2016M591519), the Heilongjiang Postdoctoral Founda-
tion (LBH-Z16069), and the National Natural Science
Foundation of Heilongjiang (Nos. B2018005 and
LC2018005).
1-(4-Methoxyphenyl)-3-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.96−7.93 (m, 2H), 7.32−7.19 (m, 5H), 6.94−
6.90 (m, 2H), 3.86 (s, 3H), 3.25 (t, J = 7.2 Hz, 2H), 3.06 (t, J = 8.0
Hz, 2H).
1-(3-Methoxyphenyl)-3-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 7.57−7.51 (m, 2H), 7.39−7.23 (m, 6H), 7.12
(dd, J = 8.4, 2.4 Hz, 1H), 3.86 (s, 3H), 3.31 (t, J = 7.2 Hz, 2H), 3.09
(t, J = 8.0 Hz, 2H).
REFERENCES
■
1-(Naphthalen-2-yl)-3-phenylpropan-1-one.14a 1H NMR (400
MHz, CDCl3, ppm): 8.34 (s, 1H), 7.93 (dd, J = 8.8, 1.6 Hz, 1H),
7.82−7.73 (m, 3H), 7.49−7.40 (m, 2H), 7.23−7.18 (m, 4H), 7.14−
7.10 (m, 1H), 3.32 (t, J = 7.2 Hz, 2H), 3.02 (t, J = 8.0 Hz, 2H).
1-(4-Fluorophenyl)-3-phenylpropan-1-one.14a 1H NMR (400
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(t, J = 8.4 Hz, 2H), 3.28 (t, J = 7.2 Hz, 2H), 3.07 (t, J = 8.0 Hz, 2H).
1,6-Diphenylhexan-1-one.32 1H NMR (500 MHz, CDCl3, ppm):
7.71 (d, J = 8.0 Hz, 2H), 7.53 (t, J = 6.5 Hz, 1H), 7.44 (t, J = 7.5 Hz,
2H), 7.26 (t, J = 8.0 Hz, 2H), 7.17 (d, J = 7.0 Hz, 3H), 2.94 (t, J = 7.5
Hz, 2H), 2.62 (t, J = 7.5 Hz, 2H), 1.80−1.74 (m, 2H), 1.70−1.64 (m,
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7.96−7.94 (m, 2H), 7.56−7.51 (m, 1H), 7.47−7.42 (m, 2H), 2.97−
2.92 (m, 2H), 1.75−1.72 (m, 2H), 1.37−1.35 (m, 4H), 0.91−0.90
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3-Cyclohexyl-1-phenylpropan-1-one.14a 1H NMR (400 MHz,
CDCl3, ppm): 7.96 (d, J = 7.6 Hz, 2H), 7.56 (t, J = 7.6 Hz, 1H), 7.46
(t, J = 7.6 Hz, 2H), 2.98 (t, J = 7.6 Hz, 2H), 1.78−1.61 (m, 7H),
1.26−1.14 (m, 4H), 0.99−0.91 (m, 2H).
1,3-Diphenylbutan-1-one.14a 1H NMR (400 MHz, CDCl3, ppm):
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