Rhodium-catalyzed cross-coupling reactions of carboxylate and organoboron compounds via chelation-assisted C-C bond activation

Article abstract of DOI:10.1021/om300994j

A new rhodium-catalyzed decarbonylated coupling reaction of ethyl benzo[h]quinoline-10-carboxylate and organoboron compounds that occurs through chelation-assisted sp² C-COOEt bond activation was described. In this system CuCl played a very important role, and a five-membered rhodacycle was also involved as a key intermediate. Various functionalities were compatible in the reaction, and the desired products were obtained in good to excellent yields. DFT calculations on the mechanisms of this reaction using a Rh(I) model catalyst have also been carried out.

Full text of DOI:10.1021/om300994j

Article
pubs.acs.org/Organometallics
Rhodium-Catalyzed Cross-Coupling Reactions of Carboxylate and
Organoboron Compounds via Chelation-Assisted C−C Bond
Activation
Jingjing Wang, Bowen Liu, Haitao Zhao,* and Jianhui Wang*
Department of Chemistry, College of Science, Tianjin University, Tianjin 300072, China
S
* Supporting Information
ABSTRACT: A new rhodium-catalyzed decarbonylated coupling
reaction of ethyl benzo[h]quinoline-10-carboxylate and organo-
boron compounds that occurs through chelation-assisted sp2 C−
COOEt bond activation was described. In this system CuCl played
a very important role, and a five-membered rhodacycle was also
involved as a key intermediate. Various functionalities were
compatible in the reaction, and the desired products were obtained in good to excellent yields. DFT calculations on the
mechanisms of this reaction using a Rh(I) model catalyst have also been carried out.
through chelation-assisted sp3 C−COOEt activation.12 How-
INTRODUCTION
■
ever, activation of an sp2 C−COOEt of this type remains a
Carbon−carbon bond cleavage reactions catalyzed by transition
contemporary challenge since the sp2 C−COOEt bond is
known to be stronger than the sp3 C−COOEt bond.
Considering the ubiquity of esters in organic molecules and
the inherently neutral conditions of the decarboxylative
reaction, developing cross-coupling reactions that use esters
as the counterpart is very attractive.
Since benzo[h]quinoline is a good reagent for metal-directed
reactions, many research groups have developed its coupling
reactions with haloarenes,13 arylenes,14 substituted benzoyl
peroxides,15c substituted benzoyl chlorides,15a substituted
benzoic anhydrides,15d and phenylmagnesium bromides15b,e
to obtain 10-substituted benzo[h]quinoline derivatives through
catalyzed C−H bond activations (Scheme 1). Herein, we
describe a new rhodium-catalyzed decarbonylated coupling
reaction of benzo[h]quinoline-10-carboxylic acid ethyl ester
and arylboronic acid that occurs through chelation-assisted sp2
C−COOEt bond activation (Scheme 1).
metals have attracted much attention in recent years1 since they
allow chemists to build complex molecules through nontradi-
tional retrosynthetic disconnections.2 Traditionally, C−C bond
cleavage has been achieved by the oxidative cyclometalation of
ring-strained three- or four-membered-ring compounds to form
more stable metallacyclic complexes.3 In these reactions, the
released energy helps to overcome the high kinetic barriers in
the activation step. Directing a metal to a particular C−C bond
using functional groups is another strategy that is commonly
used for unstrained C−C bond activation.4 Many important
reaction models based on chelation-assisted C−C activation
have also been developed recently.5 The discovery of these C−
C activation reactions has greatly expanded the methods
available for the construction of complex molecules. A wide
variety of efficient methods based on C−C bond activations is
highly desirable in order to facilitate the use of unstrained C−C
σ bonds as versatile synthons. This is currently an area of
intense focus.
The intermediates that form after the C−C bond cleavage of
carbon−nitrile (C−CN) bonds,6 the C−C bond cleavage of
tertiary alcohols (C−CR2OH),7 the decarbonylation of
aldehydes (C−CHO),8 and the decarboxylation of acids (C−
COOH)9 and anhydrides (C−COOCOR)10 are important
synthons for the construction of new compounds. These in situ
generated intermediates have been used for transition-metal-
catalyzed C−C bond formation reactions using arylboronic
acids,6e,9b,e,10 haloarenes,7a−d and arylsilanes.6a However,
reports on cross-coupling reactions using metal intermediates
generated via the decarboxylation of the carbon carbonyl group
(C−COOR) of an ester are few.11 Some active esters, for
example, 4-nitrophenyl esters11b and isopropenyl esters, have
been used in decarbonylative Heck reactions.11c When there is
a directing group located at an appropriate position, an sp3 C−
COOEt undergoes a coupling reaction with arylboronic acid
RESULTS AND DISCUSSION
■
In order to probe the possibility of a transition-metal-catalyzed
decarbonylated coupling reaction via sp2 C−COOEt bond
activation, ethyl benzo[h]quinoline-10-carboxylate (1a) and
phenylboronic acid (2a) were chosen as a model system, and
the catalyst activity in the presence of different transition metal
catalysts under various reaction conditions was examined. The
results are summarized in Table 1. Since rhodium complexes
are known to activate C−C bonds through the directing group,
rhodium complexes were tried first. However, when
RhCl3·3H2O, Rh2(COD)2Cl2, or (PPh3)3RhCl was used as
the catalyst, the cross-coupling reactions of 1a and 2a
Received: October 22, 2012
Published: December 12, 2012
© 2012 American Chemical Society
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Scheme 1. Cross-Coupling Reactions through C−H and C−C Activations
improved the yield of the reaction to 68% in 30 h (Table 1,
entry 5). When 0.5 or 1.0 equiv of CuBr was used instead of
CuI, the reaction of 1a and 2a gave the product 3aa in 60% and
87% yields in 30 h, respectively. CuCl was also found to
accelerate the reaction (Table 1, entries 8 and 9). The highest
yield (97%) occurred for the reaction using (PPh3)3RhCl as the
catalyst with 1.0 equiv of CuCl as the additive (Table 1, entry
9). Other compounds that are often used as additives in the
cross-coupling reactions of arylboronic acids, such as Cu-
(OAc)2·H2O, (NH4)2S2O8, K2S2O8, and Ag2O, were found to
prevent the desired reaction (Table 1, entries 11−14). Some
other transition metal complexes such as Ni and Pd complexes
were also tested for the activation of the sp2 C−COOEt bond,
but failed to give any of the desired product (Table 1, entries
15−18) under similar reaction conditions. It should be noted
that the cross-coupling reaction of 1a and 2a did not proceed
when only CuCl was used as the catalyst. Thus, (PPh3)3RhCl as
the catalyst in combination with CuCl (1.0 equiv) was selected
as the optimal catalytic system for the current transformation.
With the optimized catalytic system in hand, the effects of
various arylboronic acids on this cross-coupling reaction were
investigated, and the results are shown in Table 2. The reaction
of 1a with phenylboronic acid or sodium tetraphenylborate
proceeded smoothly to give the corresponding products 3aa in
95% or 91% yield, respectively (3aa, Table 2). Other esters,
such as phenyl benzo[h]quinoline-10-carboxylate 1h also
reacted with phenylboronic acid to give the desired product
3aa in 81% yield. Phenylboronic acids with a methyl group at
the para- or meta-positions also showed good reactivity with 1a,
giving the desired coupling product in 75% or 72% yields,
respectively (3ac, 3ad, Table 2). However, when there was a
methyl group at the ortho-position, the yield of the reaction of
the substituted phenylboronic acid with 1a decreased
dramatically to 38% (3ab, Table 2). These results suggest
that the steric effect of the arylboronic acid is a key factor for
controlling reactivity.
Table 1. Optimization of the Reaction Conditions for Cross-
Coupling of Phenylboronic Acid and 1a
a
a,b
entry
catalyst
additive (equiv)
time (h) yield (%)
1
RhCl3·3H2O
Rh2(COD)2C12
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
(PPh3)3RhCl
NiCl2(dppe)
Pd(OAc)2
48
48
48
30
30
30
30
30
30
48
48
48
48
48
48
48
48
48
48
15
31
40
50
68
60
87
76
97
95
<10
<10
<10
<10
0
2
3
4
Cul (0.5)
5
Cul (1.0)
6
CuBr (0.5)
CuBr (1.0)
CuCl (0.5)
CuCl (1.0)
Cul (1.0)
7
8
9
10
11
12
13
14
15
16
17
18
19
Cu(OAc)2 (1.0)
(NH4)2S2O8 (1.0)
K2S2O8 (1.0)
Ag2O (1.0)
CuCl (1.0)
CuCl (1.0)
CuCl (1.0)
CuCl (1.0)
CuCl (1.0)
0
Pd(OAc)2
0
Pd(PPh3)4
0
0
a
Reaction conditions: 1a (0.10 mmol), 2a (0.20 mmol), catalyst (10.0
b
mol %), toulene (1.0 mL), 130 °C. Isolated yields.
proceeded slowly to give the desired product in 15%, 31%, or
40% yield, respectively (Table 1, entries 1−3). This indicates
that the cleavage of the sp2 C−COOEt did not easily occur.
When 0.5 equiv of CuI was introduced into the reaction system
as an additive, the reaction using the (PPh3)3RhCl complex as
the catalyst proceeded faster to give the product in moderate
yield (50%) after 30 h, and when the reaction time was
prolonged to 48 h, a high yield (95%) was obtained (Table 1,
entries 4 and 10). Increasing the amount of CuI to 1.0 equiv
Unsurprisingly, 3,5-dimethylphenylboronic acid also reacted
with 1a to give the desired product 3ae in 81% yield.
Phenylboronic acids with a MeO group at the meta- or para-
positions reacted smoothly with 1a to give the desired coupling
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a
Table 2. Direct Functionalization of 1a with Various Substituted Phenylboronic Acid Reagents
a
Reaction conditions: ethyl benzo[h]quinoline-10-carboxylate (0.1 mmol), substituted phenylboronic acid (0.2 mmol), Rh(PPh3)3Cl (0.01 mmol),
b
c
CuCl (0.1 mmol), and toluene (0.3 mL), 130 °C, 30 h. Isolated yields based on ethyl benzo[h]quinoline-10-carboxylate are given. Phenyl
benzo[h]quinoline-10-carboxylate as the substrate. Sodium tetraphenylborate as the substrate.
d
products in yields of 90% and 93%, respectively (3af, 3ag,
Table 2), indicating that electron-donating substituents on the
phenyl ring of the arylboronic acids have no effect on its
reactivity with 1a. Gratifyingly, phenylboronic acids bearing
electron-withdrawing groups, such as F, CF3, OCF3, and NO2,
also reacted smoothly with 1a to give the coupling product in
good to excellent yields, indicating that the electron density of
the phenyl group of the arylboronic acids does not have a
significant effect on the efficiency of the transformation (3ah−
3an, Table 2). In addition, 4-(ethoxycarbonyl)phenylboronic
acid also reacted with 1a to give the desired product 3ao in 50%
yield. In this reaction, the ester group at the 10-position of the
benzo[h]quinoline acted as a leaving group, but the ester
substitution group on the arylboronic acid was retained,
illustrating the important role of the coordinated nitrogen
atom in the cleavage of the sp2 C−COOEt bond. The reaction
of phenylboronic acid with a −Cl or −Br at the para-position
afforded the desired product 3ap or 3aq in 47% and 59% yield,
respectively. Like other rhodium catalysis systems, −Cl or −Br
substituents on the substrate survive in the catalysis process,
which may allow for further modification of the product.16
A
reaction of 4-biphenylboronic acid with 1a gave the cross
product in 69% yield (3ar, Table 2). β-Naphthaleneboronic
acid displayed a high reactivity to give the cross product in high
yield (87%), whereas α-naphthaleneboronic acid showed no
reactivity with 1a (3as and 3at, Table 2), which again indicates
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Figure 1. Proposed mechanism for rhodium-catalyzed cross-coupling reactions of ethyl benzo[h]quinoline-10-carboxylate and phenylboronic acid
via C−C bond cleavage.
that steric hindrance prevents the cross-coupling reaction.
Unfortunately, pyridin-2-ylboronic acid did not react with 1a to
give any cross-coupling product (3au, Table 2). Although the
exact reason is not known at present, the competition between
the N heteroatom on the pyridyl ring and the directing group
on the substrate for coordination with the metal center of the
catalyst is highly suspected. The (2-methylallyl)boronic acid is
also not suitable for the cross-coupling reaction with 1a; no
desired product was isolated (3av, Table 2).
The scope of the benzo[h]quinoline moiety was also
investigated (3ba−3ga, Table 2). To our satisfaction, a methyl
substituent at the 6-position, named ethyl 6-methylbenzo[h]-
quinoline-10-carboxylate (3b), did not affect the reaction with
phenylboronic acid, and the desired cross-coupling product was
obtained in 92% yield (3ba, Table 2). When the ethyl
benzo[h]quinoline-10-carboxylate compound with a phenyl
group at the 5-position (1c) was used as the reaction partner,
the reactions with phenylboronic acid, (3,4-difluorophenyl)-
boronic acid, and (3-methylphenyl)boronic acid gave the
corresponding cross-coupling products in 83%, 54%, and 80%
yields, respectively (3ca, 3cd, and 3cl, Table 2). The yields of
these reactions are slightly lower than those with the
unsubstituted ethyl benzo[h]quinoline-10-carboxylate, indicat-
ing that a phenyl ring substituent at the 5-position is
unfavorable for C−C bond cleavage in these reactions.
Replacing the phenyl group with a 4-fluorophenyl group at
the 5-position of the ethyl benzo[h]quinoline-10-carboxylate
(1f) gave the product in 48% yield (3df, Table 2) in the
reaction with (3-methylphenyl)boronic acid. This is lower than
the yield with 1c, indicating that a low electron density on the
benzo[h]quinoline ring is not good for the cross-coupling
reaction. However, 5-(naphthalen-2-yl)benzo[h]quinoline (1e)
with a naphthalen-2-yl group at the 5-position reacted with
(3,4-difluorophenyl)boronic acid to give the cross-coupling
product in 89% yield, which is comparable with the yield for 1a.
This may be because the oblique state of the naphthalen-2-yl
substitution group has little effect on the benzo[h]quinoline
ring. An electron-donating group, such as a methoxyl group,
substituted at the 7-position of the benzo[h]quinoline ring did
not affect the reaction with the phenylboronic acid, and the
desired product was obtained in 95% yield, which is comparable
with yields for 1a (3da, Table 2). Ethyl 7-phenylbenzo[h]-
quinoline-10-carboxylate, with a Ph group at the 7-position of
the benzo[h]quinoline ring, also reacted with phenylboronic
acid to give the desired product 3fd in 48% yield. These
experiments indicate that a high electron density on the
benzo[h]quinoline ring helps cleave the C−COOEt bond to
give the coupling products in higher yields.
On the basis of these experiments, the plausible catalytic
mechanism (two different pathways) is proposed and shown in
Figure 2. The mechanistic pathway for the formation of 3aa
involves the following steps: First precoordination of the
nitrogen atom of substrate 1a to the Rh metal center gives
complex A in the presence of CuCl, which is a known reagent
for scavenging and reclaiming phosphines.17 Subsequently, the
oxidative addition of the C−C bond to the Rh(I) metal center
in A takes place to form Rh(III) complex B (in path a).4
Migration of the ethoxyl group of the ester fragment to the
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Figure 2. Calculated energy profiles for the pathway of the C−C activation reaction catalyzed by Rh(I). The relative free energies and electronic
energies (in parentheses) are given in kcal/mol.
Rh(III) metal center is accompanied by the elimination of PPh3
and generates the Rh(III) intermediate C, in which the Rh(III)
center is coordinated with a N atom, a carbon anion, an ethoxy
group, a chloride, a carbonyl, and a triphenylphosphane to form
an octahedral structure. According to some literature reports,11
the important intermediate C can also be generated via the
following two steps (path b): First, the insertion of a Rh(I)
metal into the C(O)−OEt group in complex A gives
intermediate B′. Second, after the elimination of PPh3, the
migration of the carbonyl group of the ester fragment in B′ to
the Rh(III) metal center takes place to form the Rh(III)
intermediate C (path b). Next, the dissociation of CO in the
intermediate C formed via path a or path b gives complex D;
this process may be assisted by CuCl through the formation of
a thermodynamically stable copper carbonyl complex. Trans-
metalation of phenylboronic acid to complex D gives the
phenyl rhodium complex F by elimination of ethyl dihydrogen
borate E. Finally, the reductive elimination of the phenyl group
and the benzo[h]quinoline ring from intermediate F affords the
desired product 3aa, and the catalytic intermediate further
coordinates with 1a to regenerate A for another cycle.
To gain a better understanding of the catalytic mechanism,
DFT calculations were carried out using the B3LYP hybrid
functional.18 The computed route of the model reaction
between a simplified methyl benzo[h]quinoline-10-carboxylate
and RhCl(PH3)3 is shown in Figure 2. The calculated results
show that this coupling reaction goes through a kinetically and
thermodynamically favorable pathway. In path a, the barrier for
the oxidative addition to the sp2 C−C(OOMe) bond in I to
give II is 22.3 kcal/mol. Step I to II is exergonic by 7.0 kcal/
mol. A PH3 ligand dissociates from II to form III. Then, the
methoxyl group of the ester fragment in III migrates to the
Rh(III) metal center to give the carbonyl-coordinated IV,
which goes through the TS(3−4) (transition state from III to
IV) with a free energy increase of 22.4 kcal/mol. In path b, the
barrier for the oxidative addition to the C−O bond in I to give
II′ is 24.4 kcal/mol. A PH3 ligand dissociates from II′ to form
III′. Then, the CO group in III′ migrates to the Rh(III) metal
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noted, all reactions were performed under an atmosphere of dry N2
with oven-dried glassware and anhydrous solvents. Toluene was dried
from sodium/benzophenone under a N2 atmosphere and distilled
prior to use. Reactions were monitored by analytical thin-layer
chromatography on 0.20 mm Anhui Liangchen silica gel plates, and
spots were detected by UV absorption. Silica gel (200−300 mesh)
(from Anhui Liangchen Chem. Company, Ltd.) was used for flash
chromatography. The starting materials were synthesized and purified
according to the literature procedures.19−21 Other chemicals and
reagents were obtained from commercial sources.
Ethyl Benzo[h]quinoline-10-carboxylate (1a). The product was
prepared according to the literature19 as a yellow solid (93% yield). 1H
NMR (400 MHz, CDCl3): δ 1.44 (t, J = 7.2 Hz, 3H), 4.62 (q, J = 6.8
Hz, 2H), 7.44−7.49 (m, 1H), 7.64−7.69 (m, 3H), 7.75−7.80 (m, 1H),
7.91−7.93 (m, 1H), 8.11 (t, J = 8.0 Hz, 1H), 8.88 (dd, J = 4.0 Hz, 2.0
Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 172.2, 147.5, 144.9, 135.3,
133.8, 132.4, 129.1, 127.5, 127.2, 126.7, 126.0, 125.9, 121.8, 61.3, 14.1.
IR (KBr): ν 3054, 1719, 1603, 1442, 1345, 1152, 1087, 1023, 845, 699
cm−1. HRMS (ESI) m/z: 252.1099 [M + H+] (calcd 252.0946). Anal.
Found (calcd) for C16H13NO2 C, 76.52 (76.48); H, 5.25 (5.21); N,
5.59 (5.57).
center in IV, which goes through TS′(3−4), with a free energy
of 47.2 kcal/mol. The free energy in path b is significantly
higher than that in path a. On the basis of this data, the reaction
through the oxidative addition to the C−O bond (path b) is not
a kinetically and thermodynamically favorable pathway in the
current reaction system. Path a is a more favorable process and
is the dominant contribution to the formation of the title
product. The free energy (−4.4 kcal/mol) of the subsequent
dissociation of CO from IV to give the carbonyl-free
intermediate V (which is assisted by CuCl) is significantly
lower than that of the reaction without the assistance of CuCl
(11.7 kcal/mol). The addition of CuCl is important for
reducing the energy barrier of the transition step, which also
explain why CuCl accelerates the rhodium-catalyzed decarbonyl
coupling reaction. The calculations give a barrier of 15.6 kcal/
mol for the transmetalation step from V to VI, which is not
surprising. Subsequent reductive elimination through TS(8−9)
affords the desired product X, and catalyst I is regenerated with
a barrier of 19.6 kcal/mol. The total reaction is exergonic by
29.1 kcal/mol, and the overall reaction barrier for the whole
reaction via path a is 24.8 kcal/mol.
Ethyl 6-Methylbenzo[h]quinoline-10-carboxylate (1b). The prod-
uct was prepared according to the literature19,21 as a yellow solid (95%
1
yield). H NMR (400 MHz, CDCl3): δ 1.43 (t, J = 7.2 Hz, 3H), 2.66
More experiments were conducted to gain further evidence
for the proposed reaction mechanism. First, the reaction
mixture was monitored by IR. An absorption peak at 1978 cm−1
appeared at the start of the reaction and slowly increased during
the reaction process, indicating the formation of metal carbonyl
complexes. Furthermore, after the completion of the catalytic
reaction, carbonyl rhodium complex (Ph3P)2Rh(CO)Cl (4),18
a known complex, was isolated and identified by single-crystal
X-ray diffraction (see Supporting Information for details).
When 4 was used by itself as the catalyst for the decarbonyl
coupling reaction of 1a and phenylboronic acid under reaction
conditions similar to those for (PPh3)3RhCl, the desired
product was isolated in 38% yield. However, when 4 was used
as the catalyst in the presence of CuCl, the product yield
increased to 90%, indicating the importance of CuCl in the
regeneration of the active catalyst by the decarbonylation
reaction.
(s, 3H), 4.61 (q, J = 7.2 Hz, 2H), 7.41 (dd, J = 8.0 Hz, 4.4 Hz, 1H),
7.44 (s, 1H), 7.64−7.73 (m, 2H), 7.99 (d, J = 8.0 Hz, 1H), 8.05 (dd, J
= 6.8 Hz, 2.8 Hz, 1H), 8.81 (d, J = 4.0 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 172.3, 146.6, 144.3, 134.5, 133.7, 133.4, 132.8, 127.5, 127.1,
126.6, 125.7, 125.5, 125.3, 121.8, 61.2, 19.8, 14.1. IR (KBr): ν 3052,
1725, 1583, 1418, 1360, 1205, 1118, 1105, 1053, 1027, 735, 705 cm−1.
HRMS (ESI) m/z: 266.1184 [M + H+] (calcd 266.1103); Anal. Found
(calcd) for C17H15NO2 C, 76.99 (76.96); H, 5.78 (5.70); N, 5.30
(5.28).
Ethyl 5-Phenylbenzo[h]quinoline-10-carboxylate (1c). The prod-
uct was prepared according to the literature19,20 as a yellow solid (87%
1
yield). H NMR (400 MHz, CDCl3): δ 1.48 (t, J = 6.4 Hz, 3H), 4.66
(q, J = 6.8 Hz, 2H), 7.45−7.57 (m, 7H), 7.69−7.74 (m, 2H), 7.80 (s,
1H), 8.24 (t, J = 6.4 Hz, 1H), 8.94 (d, J = 3.2 Hz, 1H). 13C NMR (100
MHz, CDCl3): δ 172.3, 147.4, 145.3, 139.0, 138.4, 134.1, 133.4, 132.5,
130.0, 129.9, 129.4, 128.6, 128.5, 127.9, 127.7, 126.3, 126.1, 121.8,
61.4, 14.3. IR (KBr): ν 3053, 1725, 1579, 1441, 1365, 1283, 1200,
1145, 1108, 1057, 1027, 733, 702 cm−1. HRMS (ESI) m/z: 328.1339
[M + H+] (calcd 328.1259). Anal. Found (calcd) for C22H17NO2: C,
80.77 (80.71); H, 5.25 (5.23); N, 4.31 (4.28).
CONCLUSIONS
■
Ethyl 5-(4-Fluorophenyl)benzo[h]quinoline-10-carboxylate (1d).
The product was prepared according to the literature19,20 as a yellow
solid (83% yield). 1H NMR (400 MHz, CDCl3): δ 1.46 (t, J = 7.2 Hz,
3H), 4.63 (q, J = 7.2 Hz, 2H), 7.19−7.27 (m, 2H), 7.47−7.51 (m,
3H), 7.71−7.77 (m, 3H), 7.98 (d, J = 7.6 Hz, 1H), 8.18 (d, J = 8.4 Hz,
1H), 8.93 (dd, J = 4.0 Hz, 1.2 Hz, 1H). 13C NMR (100 MHz, CDCl3):
We have developed an efficient rhodium(I)-catalyzed decarbon-
ylative arylation that occurs through C−C and C−B cleavages
with the assistance of an N-containing directing group. A wide
variety of functional groups can be tolerated in the reaction,
and the desired products can be obtained in good to excellent
yields. The mechanism of the coupling reaction was explained
by using DFT calculations. Currently work is underway in our
laboratory to discover other directing groups that will expand
the utility of this methodology.
1
δ 172.2, 162.6 (d, JC−F = 245.9 Hz), 147.5, 145.3, 137.3, 135.0 (d,
3JC−F = 3.2 Hz), 133.7, 133.3, 132.6, 131.5, 131.4, 129.3, 127.8, 127.7,
2
127.4, 126.2, 121.8, 115.5 (d, JC−F = 21.2 Hz), 61.4, 14.2. 19F NMR
(376 MHz, CDCl3): δ −114.1 (m, 1F). IR (KBr): ν 3132, 1728, 1506,
1398, 1283, 1222, 1145, 1107, 1016, 837, 734, 668 cm−1. HRMS (ESI)
m/z: 346.1247 [M + H+] (calcd 346.1165). Anal. Found (calcd) for
C22H16FNO2: C, 76.61 (76.51); H, 4.69 (4.67); N, 4.06 (4.06).
Ethyl 5-(Naphthalen-2-yl)benzo[h]quinoline-10-carboxylate (1e).
The product was prepared according to the literature19,20 as a yellow
solid (92% yield). 1H NMR (400 MHz, CDCl3): δ 1.46 (t, J = 7.2 Hz,
3H), 4.63 (q, J = 7.2 Hz, 2H), 7.45 (dd, J = 8.0 Hz, 4.0 Hz, 1H), 7.55−
7.59 (m, 2H), 7.62 (dd, J = 8.4 Hz, 1.6 Hz, 1H), 7.71−7.76 (m, 2H),
7.88 (s, 1H), 7.91−8.03 (m, 5H), 8.25 (dd, J = 8.0 Hz, 1.6 Hz, 1H),
8.92 (dd, J = 4.4 Hz, 1.6 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ
172.3, 147.4, 145.4, 138.4, 136.6, 134.1, 133.5, 133.4, 132.8, 132.6,
129.3, 128.8, 128.0, 127.9, 127.8, 127.7, 127.4, 126.6, 126.4, 126.2,
121.8, 61.4, 14.3. IR (KBr): ν 3055, 1725, 1598, 1516, 1427, 1365,
1283, 1201, 1145, 1105, 1058, 1027, 822, 805, 734 cm−1. HRMS (ESI)
m/z: 378.1492 [M + H+] (calcd 378.1416). Anal. Found (calcd) for
C26H19NO2: C, 82.75 (82.74); H, 5.10 (5.07); N, 3.75 (3.71).
EXPERIMENTAL SECTION
■
1
General Information. H NMR, 19F NMR, and 13C NMR were
obtained on a 400 MHz spectrometer with CDCl3 as solvent. The
chemical shifts are reported in ppm relative to CHCl3 (δ = 7.26) for
1H NMR and relative to the central CDCl3 resonance (δ = 77.0) for
13C NMR. For 19F NMR, (trifluoromethyl)benzene was used as an
external standard. NMR data of known compounds are in agreement
with literature values. Coupling constants (J) are quoted in Hz at 400
MHz for 1H. Infrared spectra were recorded on a Perkin-Elmer model
1600 FT-IR spectrophotometer and Nicolet Magna 550 FT-IR
1
spectrophotometer. Conversions were obtained by H NMR analysis
of the sample. Multiplicities are reported as follows: singlet (s),
doublet (d), doublet of doublets (dd), doublet of doublet of doublets
(ddd), triplet (t), quartet (q), and multiplet (m). Unless otherwise
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Organometallics
Article
Ethyl 7-Methoxybenzo[h]quinoline-10-carboxylate (1f). The
product was prepared according to the literature19,21 as a yellow
solid (95% yield). 1H NMR (400 MHz, CDCl3): δ 1.40 (t, J = 7.2 Hz,
3H), 4.03 (s, 3H), 4.56 (q, J = 7.2 Hz, 2H), 7.06 (d, J = 8.4 Hz, 1H),
7.49 (dd, J = 8.0 Hz, 4.4 Hz, 1H), 7.63 (d, J = 8.0 Hz, 1H), 7.70 (d, J =
9.2 Hz, 1H), 8.15 (dd, J = 8.4 Hz, 1.2 Hz, 1H), 8.29 (d, J = 9.2 Hz,
1H), 8.88 (dd, J = 4.0 Hz, 1.2 Hz, 1H). 13C NMR (100 MHz, CDCl3):
δ 172.4, 156.2, 147.5, 144.8, 135.4, 129.1, 127.1, 126.7, 125.1, 125.0,
124.9, 121.9, 121.3, 106.3, 61.2, 55.8, 14.2. IR (KBr): ν 3044, 1710,
1581, 1512, 1436, 1365, 1283, 1249, 1204, 1180, 1121, 1053, 1030,
839, 807, 752 cm−1. HRMS (ESI) m/z: 282.1130 [M + H+] (calcd
282.1052). Anal. Found (calcd) for C17H15NO3: C, 72.59 (72.58); H,
5.37 (5.37); N, 5.01 (4.98).
1H). 13C NMR (CDCl3, 100 MHz): δ 146.9, 146.8, 143.4, 141.7,
135.1, 135.0, 131.6, 129.1, 128.6, 128.3, 128.0, 127.7, 127.2, 127.0,
125.8, 120.9, 21.2. IR (KBr): ν 3046, 2921, 2856, 1601, 1567, 1512,
1443, 1419, 1324, 1261, 1181, 922, 837, 814, 719, 662 cm−1. HRMS
(ESI) m/z: 270.1281 [M + H+] (calcd 270.1204). Anal. Found (calcd)
for C20H15N: C, 89.28 (89.19); H, 5.65 (5.61); N, 5.26 (5.20).
10-(m-Tolyl)benzo[h]quinoline (3ad): white solid (yield: 72%). 1H
NMR (CDCl3, 400 MHz): δ 2.40 (s, 3H), 7.14−7.33 (m, 5H), 7.55
(d, J = 7.2 Hz, 1H), 7.65−7.70 (m, 2H), 7.85 (d, J = 8.8 Hz, 1H), 7.91
(d, J = 8.0 Hz, 1H), 8.08 (d, J = 8.0 Hz, 1H), 8.44 (dd, J = 4.0, 1.2 Hz,
1H). 13C NMR (CDCl3, 100 MHz): δ 146.8, 146.2, 141.8, 139.4,
135.1, 135.0, 131.4, 129.3, 128.7, 128.2, 127.8, 127.1, 126.9, 126.3,
125.9, 125.8, 121.0, 21.5. IR (KBr): ν 3032, 2923, 1569, 1402, 1260,
1094, 1021, 833, 796, 729, 699 cm−1. HRMS (ESI) m/z: 270.1278 [M
+ H+] (calcd 270.1204). Anal. Found (calcd) for C20H15N: C, 89.25
(89.19); H, 5.61 (5.61); N, 5.30 (5.20).
Ethyl 7-Phenylbenzo[h]quinoline-10-carboxylate (1g). The prod-
uct was prepared according to the literature19,21 as a yellow solid (87%
1
yield). H NMR (400 MHz, CDCl3): δ 1.46 (t, J = 7.2 Hz, 3H), 4.64
10-(3,5-Dimethylphenyl)benzo[h]quinoline (3ae): white solid
(yield: 81%). H NMR (CDCl3, 400 MHz): δ 2.36 (s, 6H), 7.00 (s,
(q, J = 7.2 Hz, 2H), 7.47−7.55 (m, 6H), 7.62−7.67 (m, 2H), 7.75 (d, J
= 7.6 Hz, 1H), 7.88 (d, J = 9.2 Hz, 1H), 8.14 (d, J = 8.0 Hz, 1H), 8.92
(d, J = 4.4 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 172.3, 147.5,
145.0, 141.8, 140.0, 135.3, 131.8, 130.0, 128.5, 128.3, 128.1, 127.6,
126.4, 125.8, 125.5, 125.4, 122.0, 61.4, 14.2. IR (KBr): ν 3056, 1724,
1619, 1515, 1423, 1300, 1265, 1199, 1139, 1111, 1016, 835, 748, 703
cm−1. HRMS (ESI) m/z: 328.1293 [M + H+] (calcd 328.1259). Anal.
Found (calcd) for C22H17NO2: C, 80.75 (80.71); H, 5.27 (5.23); N,
4.28 (4.28).
1
3H), 7.34 (dd, J = 8.0 Hz, 4.4 Hz, 1H), 7.56 (d, J = 6.4 Hz, 1H), 7.65−
7.70 (m, 2H), 7.85 (d, J = 8.8 Hz, 1H), 7.90 (d, J = 7.2 Hz, 1H), 8.09
(dd, J = 8.0 Hz, 1.2 Hz, 1H), 8.47 (dd, J = 4.0, 1.6 Hz, 1H). 13C NMR
(CDCl3, 100 MHz): δ 146.9, 146.8, 146.1, 141.9, 136.5, 135.1, 135.0,
131.5, 129.0, 128.3, 127.7, 127.3, 127.1, 126.9, 126.5, 125.7, 120.9,
21.4. IR (KBr): ν 3045, 2920, 1600, 1557, 1413, 1326, 909, 835, 732,
635 cm−1. HRMS (ESI) m/z: 284.1436 [M + H+] (calcd 284.1361).
Anal. Found (calcd) for C21H17N: C, 89.13 (89.01); H, 6.09 (6.05); N,
4.95 (4.94).
Phenyl Benzo[h]quinoline-10-carboxylate (1h): yellow solid
1
(yield: 81%). H NMR (400 MHz, CDCl3): δ 7.28 (t, J = 4.8 Hz,
10-(3-Methoxyphenyl)benzo[h]quinoline (3af): white solid (yield:
1H), 7.47−7.53 (m, 4H), 7.56 (dd, J = 5.2 Hz, 2.8 Hz, 1H), 7.75−7.79
(m, 2H), 7.85−7.89 (m, 2H), 8.05 (dd, J = 5.2 Hz, 0.4 Hz, 1H), 8.22
(dd, J = 5.2 Hz, 1.2 Hz, 1H), 9.00 (dd, J = 2.8 Hz, 1.2 Hz, 1H). 13C
NMR (100 MHz, CDCl3): δ 170.0, 151.6, 147.8, 144.9, 135.6, 133.9,
131.6, 129.7, 129.3, 127.8, 127.6, 127.4, 127.0, 126.5, 126.2, 125.4,
122.1, 121.6. IR (KBr): ν 3042, 1747, 1592, 1515, 1425, 1267, 1194,
1086, 961, 912, 837, 728 cm−1. HRMS (ESI) m/z: 300.1024 [M + H+]
(calcd 300.1019). Anal. Found (calcd) for C20H13NO2: C, 80.33
(80.25); H, 4.39 (4.38); N, 4.68 (4.68).
Experimental Procedure for the Rh-Catalyzed Benzo[h]-
quinoline-10-carboxylic Acid Ethyl Ester with Substituted
Phenylboronic Acids. To an oven-dried screwed vial were added
substituted ethyl benzo[h]quinoline-10-carboxylate (0.1 mmol),
substituted phenylboronic acid (0.2 mmol), copper(I) chloride (9.9
mg, 0.1 mmol), Rh(PPh3)3Cl (9.3 mg, 0.01 mmol), and toluene (0.3
mL) under a nitrogen atmosphere. The mixture was vigorously stirred
at 130 °C to the end of the reaction. Organic solvents were removed in
vacuo, and then the residue was purified by a silica gel column
chromatography to give the desired product.
1
90%). H NMR (CDCl3, 400 MHz): δ 3.80 (s, 3H), 6.92−6.98 (m,
3H), 7.31−7.34 (m, 2H), 7.57 (d, J = 7.2 Hz, 1H), 7.67−7.71 (m,
2H), 7.86 (d, J = 8.4 Hz, 1H), 7.93 (d, J = 7.2 Hz, 1H), 8.08 (d, J = 7.6
Hz, 1H), 8.48 (d, J = 2.8 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ
159.0, 147.8, 146.9, 146.7, 141.5, 135.1, 134.9, 131.2, 129.0, 128.3,
128.2, 127.9, 127.2, 126.9, 125.9, 121.4, 121.0, 114.4, 111.5, 55.2. IR
(KBr): ν 3046, 2934, 1573, 1225, 1170, 1039, 1043, 831, 781, 728,
708, 619 cm−1. HRMS (ESI) m/z: 286.1231 [M + H+] (calcd
286.1154). Anal. Found (calcd) for C20H15NO: C, 84.19 (84.19); H,
5.35 (5.30); N, 4.90 (4.91).
10-(4-Methoxyphenyl)benzo[h]quinoline (3ag): white solid (yield:
1
93%). H NMR (CDCl3, 400 MHz): δ 3.91 (s, 3H), 6.95 (d, J = 8.4
Hz, 2H), 7.28−7.34 (m, 3H), 7.54 (d, J = 7.2 Hz, 1H), 7.65−7.69 (m,
2H), 7.85 (d, J = 8.8 Hz, 1H), 7.90 (d, J = 8.0 Hz, 1H), 8.08 (d, J = 8.0
Hz, 1H), 8.47 (d, J = 2.8 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ
157.9, 146.8, 141.4, 138.9, 135.1, 135.0, 131.7, 129.8, 129.1, 128.3,
127.7, 127.2, 127.0, 125.8, 121.0, 112.8, 55.3. IR (KBr): ν 3031, 2922,
1514, 1243, 1174, 1030, 824, 733, 668 cm−1. HRMS (ESI) m/z:
286.1238 [M + H+] (calcd 286.1154). Anal. Found (calcd) for
C20H15NO: C, 84.22 (84.19); H, 5.31 (5.30); N, 4.93 (4.91).
10-Phenylbenzo[h]quinoline (3aa): white solid (yield: 97% and
1
91%). H NMR (CDCl3, 400 MHz): δ 7.33 (dd, J = 8.0 Hz, 4.0 Hz,
1H), 7.37−7.45 (m, 5H), 7.58 (d, J = 7.2 Hz, 1H), 7.68−7.72 (m,
2H), 7.87 (d, J = 8.4 Hz, 1H), 7.94 (d, J = 7.6 Hz, 1H), 8.09 (dd, J =
8.0 Hz, 1.6 Hz, 1H), 8.45 (dd, J = 4.4 Hz, 1.6 Hz, 1H). 13C NMR
(CDCl3, 100 MHz): δ 146.8, 146.4, 141.6, 135.1, 134.9, 131.4, 128.9,
128.6, 128.2, 127.9, 127.3, 127.1, 126.9, 125.8, 125.6, 121.0. IR (KBr):
ν 3049, 1583, 1509, 1440, 1417, 836, 756, 730, 698, 616 cm−1. HRMS
(ESI) m/z: 256.1125 [M + H+] (calcd 256.1048). Anal. Found (calcd)
for C19H13N: C, 89.42 (89.38); H, 5.20 (5.13); N, 5.47 (5.49).
10-(p-Tolyl)benzo[h]quinoline (3ab): pale yellow, viscous oil
10-(4-Fluorophenyl)benzo[h]quinoline (3ah): white solid (yield:
85%). 1H NMR (CDCl3, 400 MHz): δ 7.09 (t, J = 8.8 Hz, 2H), 7.29−
7.35 (m, 3H), 7.53 (dd, J = 7.2 Hz, 1.2 Hz, 1H), 7.66−7.71 (m, 2H),
7.86 (d, J = 8.8 Hz, 1H), 7.93 (d, J = 8.0 Hz, 1H), 8.09 (dd, J = 8.0 Hz,
1.6 Hz, 1H), 8.46 (dd, J = 4.0 Hz, 1.6 Hz, 1H). 13C NMR (CDCl3, 100
1
3
MHz): δ 161.5 (d, JC−F = 241.7 Hz), 146.8, 146.7, 142.2 (d, JC−F
=
3
3.3 Hz), 140.7, 135.2, 134.9, 131.4, 130.1 (d, JC−F = 7.7 Hz), 129.0,
128.2, 128.1, 127.2, 126.9, 125.9, 121.1, 114.1 (d, 2JC−F = 21.3 Hz). 19
F
NMR (376 MHz, CDCl3): δ −118.1 (m, 1F). IR (KBr): ν 3046, 1591,
1514, 1420, 1212, 1156, 1091, 832, 759, 731 cm−1. HRMS (ESI) m/z:
274.1035 [M + H+] (calcd 274.0954). Anal. Found (calcd) for
C19H12FN: C, 83.61 (83.50); H, 4.43 (4.43); N, 5.13 (5.12).
10-(3-(Trifluoromethoxy)phenyl)benzo[h]quinoline (3ai): yellow
1
(yield: 38%). H NMR (CDCl3, 400 MHz): δ 1.84 (s, 3H), 7.16−
7.32 (m, 5H), 7.46 (d, J = 7.2 Hz, 1H), 7.68−7.72 (m, 2H), 7.87 (d, J
= 8.8 Hz, 1H), 7.94 (d, J = 7.6 Hz, 1H), 8.07 (dd, J = 8.0, 1.6 Hz, 1H),
8.41 (dd, J = 4.0, 1.6 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 147.4,
146.9, 146.4, 141.0, 135.8, 134.9, 134.6, 130.6, 129.4, 128.6, 128.3,
127.9, 127.8, 127.1, 126.9, 125.8, 125.7, 125.0, 120.9, 20.1. IR (KBr): ν
3046, 2922, 1417, 1257, 1134, 923, 837, 754, 732 cm−1. HRMS (ESI)
m/z: 270.1279 [M + H+] (calcd 270.1204). Anal. Found (calcd) for
C20H15N: C, 89.21 (89.19); H, 5.65 (5.61); N, 5.23 (5.20).
1
solid (yield: 83%). H NMR (400 MHz, CDCl3): δ 7.20−7.22 (m,
2H), 7.31−7.35 (m, 2H), 7.43 (t, J = 8.0 Hz, 1H), 7.53 (d, J = 7.2 Hz,
1H), 7.68−7.72 (m, 2H), 7.87 (d, J = 8.4 Hz, 1H), 7.96 (d, J = 7.6 Hz,
1H), 8.10 (dd, J = 8.0 Hz, 1.6 Hz, 1H), 8.42 (dd, J = 4.4 Hz, 1.6 Hz,
1H). 13C NMR (CDCl3, 100 MHz): δ 148.5, 148.3, 146.9, 146.4,
140.0, 135.2, 134.9, 131.1, 128.8, 128.6, 128.4, 128.1, 127.2, 127.0,
1
10-(p-Tolyl)benzo[h]quinoline (3ac): white solid (yield: 75%). H
NMR (CDCl3, 400 MHz): δ 2.49 (s, 3H), 7.23−7.36 (m, 5H), 7.57
(d, J = 7.2 Hz, 1H), 7.70 (t, J = 8.0 Hz, 2H), 7.88 (d, J = 8.8 Hz, 1H),
7.93 (d, J = 7.6 Hz, 1H), 8.11 (d, J = 6.8 Hz, 1H), 8.49 (d, J = 2.4 Hz,
126.8, 126.1, 122.1, 121.9, 121.2, 119.4 (q, JC−F = 254.7 Hz), 118.2. 19
F
NMR (376 MHz, CDCl3): δ −57.5 (s, 3F). IR (KBr): ν 3046, 2924,
1580, 1418, 1253, 1220, 1158, 914, 834, 730, 698, 625 cm−1. HRMS
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(ESI) m/z: 340.0937 [M + H+] (calcd 340.0871). Anal. Found (calcd)
for C20H12F3NO: C, 70.81 (70.79); H, 3.57 (3.56); N, 4.15 (4.13).
10-(4-(Trifluoromethyl)phenyl)benzo[h]quinoline (3aj): white
121.2, 61.0, 14.3. IR (KBr): 3047, 2958, 2927, 2870, 2853, 1711, 1607,
1398, 1270, 1176, 1102, 1020, 837, 760, 731, 708 cm−1. HRMS (ESI)
m/z: 328.1339 [M + H+] (calcd 328.1259). Anal. Found (calcd) for
C22H17NO2: C, 80.92 (80.71); H, 5.30 (5.23); N, 4.30 (4.28).
10-(4-Chlorophenyl)benzo[h]quinoline (3ap): white solid (yield:
1
solid (yield: 90%). H NMR (400 MHz, CDCl3): δ 7.34 (dd, J =
8.0 Hz, 4.0 Hz, 1H), 7.44−7.51 (m, 3H), 7.64−7.73 (m, 4H), 7.88 (d,
J = 8.8 Hz, 1H), 7.97 (d, J = 8.0 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H),
8.40 (dd, J = 4.0 Hz, 1.6 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ
150.2, 146.9, 146.4, 140.2, 135.3, 134.9, 131.0, 128.9, 128.8, 128.5,
128.2, 127.9, 127.7 (q, JC−F = 31.8 Hz), 127.2, 127.0, 126.1, 124.8 (q,
JC−F = 273.6 Hz), 124.2 (q, JC−F = 3.7 Hz), 121.2. 19F NMR (376
MHz,CDCl3): δ −61.9 (s, 3F). IR (KBr): ν 3042, 2927, 1518, 1404,
1335, 1159, 1064, 924, 834, 730, 680, 605 cm−1. HRMS (ESI) m/z:
324.0998 [M + H+] (calcd 324.0922). Anal. Found (calcd) for
C20H12F3N: C, 74.35 (74.30); H, 3.80 (3.74); N, 4.33 (4.33).
1
47%). H NMR (400 MHz, CDCl3): δ 7.29−7.40 (m, 5H), 7.51 (d, J
= 7.2 Hz, 1H), 7.67−7.72 (m, 2H), 7.86 (d, J = 8.8 Hz, 1H), 7.94 (d, J
= 7.6 Hz, 1H), 8.09 (d, J = 8.0 Hz, 1H), 8.48 (d, J = 2.8 Hz, 1H). 13C
NMR (CDCl3, 100 MHz): δ 146.9, 146.8, 146.5, 144.8, 140.3, 135.2,
134.9, 131.4, 131.2, 130.1, 130.0, 128.8, 128.2, 127.4, 127.2, 127.1,
126.9, 125.9, 121.1. IR (KBr): ν 3047, 2925, 2854, 1511, 1491, 1420,
1395, 1089, 1014, 840, 822, 731 cm−1. HRMS (ESI) m/z: 290.0745
[M + H+] (calcd 290.0658). Anal. Found (calcd) for C19H12ClN: C,
78.80 (78.76); H, 4.23 (4.17); N, 4.80 (4.83).
10-(3,5-Bis(trifluoromethyl)phenyl)benzo[h]quinoline (3ak):
white solid (yield: 95%). H NMR (400 MHz, CDCl3): δ 7.37 (dd,
10-(4-Bromophenyl)benzo[h]quinoline (3aq): white solid (yield:
59%). H NMR (400 MHz, CDCl3): δ 7.23 (d, J = 8.4 Hz, 2H), 7.34
1
1
J = 7.6 Hz, 4.0 Hz, 1H), 7.53 (d, J = 6.8 Hz, 1H), 7.73 (t, J = 8.8 Hz,
2H), 7.84−7.90 (m, 4H), 8.01 (d, J = 7.6 Hz, 1H), 8.12 (d, J = 8.0 Hz,
1H), 8.37 (d, J = 2.4 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 148.1,
146.8, 146.0, 138.4, 135.4, 135.0, 131.2, 130.4, 129.2, 128.6, 127.3,
127.1, 126.3, 125.2, 122.5, 121.5, 119.5. 19F NMR (376 MHz, CDCl3):
δ −62.5 (s, 6F). IR (KBr): ν 3042, 1640, 1514, 1378, 1277, 1171,
1126, 891, 835, 734, 625 cm−1. HRMS (ESI) m/z: 392.0885 [M + H+]
(calcd 392.0796). Anal. Found (calcd) for C21H11F6N: C, 64.50
(64.46); H, 2.83 (2.83); N, 3.55 (3.58).
(dd, J = 8.0, 4.0 Hz, 1H), 7.49−7.53 (m, 3H), 7.66−7.72 (m, 2H),
7.86 (d, J = 8.8 Hz, 1H), 7.94 (d, J = 8.0 Hz, 1H), 8.09 (d, J = 8.0 Hz,
1H), 8.47 (d, J = 2.8 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 146.8,
146.6, 145.3, 140.4, 135.2, 135.0, 131.2, 130.5, 130.3, 128.9, 128.3,
128.2, 127.2, 127.0, 126.0, 121.1, 119.6. IR (KBr): ν 3046, 1590, 1510,
1485, 1420, 1395, 1009, 922, 825, 818, 731 cm−1. HRMS (ESI) m/z:
334.0235 [M + H+] (calcd 334.0153). Anal. Found (calcd) for
C19H12BrN: C, 68.35 (68.28); H, 3.64 (3.62); N, 4.15 (4.19).
10-([1,1′-Biphenyl]-4-yl)benzo[h]quinoline (3ar): white solid
1
10-(3,4-Difluorophenyl)benzo[h]quinoline (3al): white solid
(yield: 69%). H NMR (CDCl3, 400 MHz): δ 7.32−7.40 (m, 2H),
1
(yield: 88%). H NMR (400 MHz, CDCl3): δ 7.03−7.06 (m, 1H),
7.46−7.52 (m, 4H), 7.62 (d, J = 7.2 Hz, 1H), 7.67−7.78 (m, 6H), 7.88
(d, J = 8.8 Hz, 1H), 7.95 (d, J = 7.6 Hz, 1H), 8.10 (d, J = 7.6 Hz, 1H),
8.47 (d, J = 2.4 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 146.8,
146.7, 145.5, 141.4, 141.3, 138.3, 135.1, 135.0, 131.5, 129.2, 129.0,
128.7, 128.2, 127.9, 127.2, 127.0, 126.9, 126.0, 125.9, 121.1. IR (KBr):
ν 3047, 2925, 1485, 1419, 833, 763, 733, 697 cm−1. HRMS (ESI) m/z:
332.1437 [M + H+] (calcd 332.1361). Anal. Found (calcd) for
C25H17N: C, 90.62 (90.60); H, 5.21 (5.17); N, 4.24 (4.23).
7.13−7.21 (m, 2H), 7.36 (dd, J = 8.0 Hz, 4.0 Hz, 1H), 7.50 (dd, J = 7.2
Hz, 1.2 Hz, 1H), 7.66−7.72 (m, 2H), 7.86 (d, J = 8.8 Hz, 1H), 7.95 (d,
J = 7.2 Hz, 1H), 8.11 (dd, J = 8.0 Hz, 1.6 Hz, 1H), 8.47 (dd, J = 4.0
1
Hz, 1.6 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 149.7 (dd, JC−F
=
1
244.2 Hz, 12.6 Hz), 149.0 (dd, JC−F = 243.6 Hz, 12.6 Hz), 146.9,
3
146.4, 143.1 (dd, JC−F = 6.5 Hz, 4.2 Hz), 139.4, 135.2, 134.9, 131.1,
128.8, 128.4, 128.1, 127.2, 126.9, 126.1, 124.5 (dd, 3JC−F = 5.7 Hz, 3.4
Hz), 121.2, 117.9 (d, 2JC−F = 17.3 Hz), 116.0 (d, 2JC−F = 16.9 Hz). 19
F
10-(Naphthalen-2-yl)benzo[h]quinoline (3as): yellow solid (yield:
1
NMR (376 MHz, CDCl3): δ −140.3 (m, 1F), −142.9 (m, 1F). IR
(KBr): ν 3050, 2922, 1663, 1518, 1423, 1258, 1192, 1112, 838, 814,
769, 730, 624 cm−1. HRMS (ESI) m/z: 292.0873 [M + H+] (calcd
292.0860). Anal. Found (calcd) for C19H11F2N: C, 78.35 (78.34); H,
3.87 (3.81); N, 4.83 (4.81).
87%). H NMR (CDCl3, 400 MHz): δ 7.30 (dd, J = 8.0 Hz, 4.4 Hz,
1H), 7.45 (dd, J = 8.4 Hz, 1.2 Hz, 1H), 7.48−7.53 (m, 2H), 7.65 (d, J
= 6.0 Hz, 1H), 7.71−7.79 (m, 3H), 7.89−7.93 (m, 4H), 7.97 (d, J =
7.6 Hz, 1H), 8.10 (dd, J = 8.0, 1.6 Hz, 1H), 8.33 (dd, J = 4.0 Hz, 1.6
Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ 146.9, 146.7, 144.5, 141.5,
135.1, 135.0, 133.7, 132.1, 131.9, 129.4, 129.0, 128.3, 128.1, 128.0,
127.6, 127.2, 127.1, 125.9, 125.6, 125.5, 125.4, 125.1, 121.0. IR (KBr):
ν 3048, 1557, 1418, 1125, 1015, 833, 815, 749, 730, 648 cm−1. HRMS
(ESI) m/z: 306.1275 [M + H+] (calcd 306.1204). Anal. Found (calcd)
for C23H15N: C, 90.50 (90.46); H, 4.97 (4.95); N, 4.58 (4.59).
6-Methyl-10-phenylbenzo[h]quinoline (3ba): white solid (yield:
92%). 1H NMR (400 MHz, CDCl3): δ 2.81 (s, 3H), 7.27 (dd, J = 8.0
Hz, 4.4 Hz, 1H), 7.35−7.38 (m, 3H), 7.40−7.43 (m, 2H), 7.55 (s,
1H), 7.59 (d, J = 7.2 Hz, 1H), 7.74 (t, J = 8.0 Hz, 1H), 7.99 (dd, J =
8.0 Hz, 1.2 Hz, 1H), 8.10 (d, J = 8.0 Hz, 1H), 8.36 (dd, J = 4.0 Hz, 1.2
Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 146.9, 146.3, 146.0, 142.1,
134.8, 134.3, 133.6, 131.2, 129.1, 128.7, 128.6, 127.3, 127.0, 126.9,
125.8, 125.5, 123.8, 121.1, 20.5. IR (KBr): ν 3052, 1588, 1571, 1441,
1422, 1382, 1023, 872, 829, 789, 759, 733, 698 cm−1. HRMS (ESI) m/
z: 270.1281 [M + H+] (calcd 270.1204). Anal. Found (calcd) for
C20H15N: C, 89.27 (89.19); H, 5.65 (5.61); N, 5.22 (5.20).
5,10-Diphenylbenzo[h]quinoline (3ca): ellow solid (yield: 83%).
1H NMR (400 MHz, CDCl3): δ 7.24−7.27 (m, 1H), 7.37−7.58 (m,
11H), 7.70 (t, J = 7.6 Hz, 1H), 7.82−7.94 (m, 2H), 8.15 (dd, J = 8.4,
1.2 Hz, 1H), 8.43 (dd, J = 4.0, 2.8 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 146.5, 141.7, 139.5, 137.9, 134.4, 133.5, 131.4, 130.2, 129.9,
128.7, 128.6, 128.5, 128.4, 128.3, 127.9, 127.6, 127.4, 127.3, 126.4,
125.6, 120.8. IR (KBr): ν 3054, 3025, 1568, 1513, 1490, 1387, 804,
759, 734, 700 cm−1. HRMS (ESI) m/z: 332.1439 [M + H+] (calcd
332.1361). Anal. Found (calcd) for C25H17N: C, 90.62 (90.60); H,
5.23 (5.17); N, 4.25 (4.23).
10-(3,4,5-Trifluorophenyl)benzo[h]quinoline (3am): white solid
(yield: 96%). 1H NMR (CDCl3, 400 MHz): δ 6.93 (dd, J = 8.4 Hz, 6.8
Hz, 2H), 7.38 (dd, J = 8.0 Hz, 4.4 Hz, 1H), 7.48 (d, J = 7.2 Hz, 1H),
7.66−7.73 (m, 2H), 7.86 (d, J = 8.8 Hz, 1H), 7.96 (d, J = 7.6 Hz, 1H),
8.12 (dd, J = 8.0 Hz, 1.6 Hz, 1H), 8.51 (dd, J = 4.0 Hz, 1.6 Hz, 1H).
13C NMR (CDCl3, 100 MHz): δ 151.8, 149.4, 147.1, 146.1, 142.3,
139.5, 138.5, 137.1, 135.3, 134.9, 130.8, 128.8, 128.7, 128.1, 127.3,
126.9, 126.2, 121.3, 112.9, 112.8. 19F NMR (376 MHz, CDCl3): δ
−137.2 (m, 1F), −165.7 (m, 2F). IR (KBr): ν 3052, 1613, 1528, 1423,
1246, 1033, 835, 775, 732, 660, 630 cm−1. HRMS (ESI) m/z:
310.0839 [M + H+] (calcd 310.0765). Anal. Found (calcd) for
C19H10F3N: C, 73.81 (73.78); H, 3.30 (3.26); N, 4.52 (4.53).
10-(3-Nitrophenyl)benzo[h]quinoline (3an): yellow solid (yield:
1
85%). H NMR (400 MHz, CDCl3): δ 7.34 (dd, J = 7.6 Hz, 4.4 Hz,
1H), 7.50−7.56 (m, 2H), 7.67−7.74 (m, 3H), 7.88 (d, J = 8.8 Hz,
1H), 7.99 (d, J = 8.0 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H), 8.24 (m, 2H),
8.35 (dd, J = 3.6 Hz, 1.2 Hz, 1H). 13C NMR (CDCl3, 100 MHz): δ
147.9, 147.7, 146.8, 146.2, 138.9, 135.4, 135.0, 134.9, 131.1, 128.9,
128.6, 128.2, 127.9, 127.3, 127.1, 126.2, 123.9, 121.3, 120.7. IR (KBr):
ν 3047, 1524, 1344, 837, 804, 731, 685, 618 cm−1. HRMS (ESI) m/z:
301.0978 [M + H+] (calcd 301.0899). Anal. Found (calcd) for
C19H12N2O2: C, 76.05 (75.99); H, 4.05 (4.03); N, 9.37 (9.33).
Ethyl 4-(Benzo[h]quinolin-10-yl)benzoate (3ao): yellow solid
1
(yield: 50%). H NMR (400 MHz, CDCl3): δ 1.47 (t, J = 7.2 Hz,
3H), 4.46 (dd, J = 14.4 Hz, 7.2 Hz, 2H), 7.35 (dd, J = 8.0 Hz, 4.4 Hz,
1H), 7.44 (d, J = 8.0 Hz, 2H), 7.53 (d, J = 7.2 Hz, 1H), 7.71 (d, J = 8.0
Hz, 2H), 7.89 (d, J = 8.8 Hz, 1H), 7.98 (d, J = 7.6 Hz, 1H), 8.11 (d, J
= 8.0 Hz, 2H), 8.16 (d, J = 8.0 Hz, 1H), 8.42 (d, J = 3.2 Hz, 1H). 13C
NMR (100 MHz, CDCl3): δ 166.2, 151.5, 146.8, 144.3, 135.2, 134.9,
130.9, 130.1, 130.0, 128.7, 128.7, 128.3, 128.1, 127.1, 127.0, 126.0,
5-Phenyl-10-(m-tolyl)benzo[h]quinoline (3cd): white solid (yield:
1
54%). H NMR (400 MHz, CDCl3): δ 2.43 (s, 3H), 7.19 (d, J = 7.6
Hz, 2H), 7.25−7.32 (m, 3H), 7.46−7.58 (m, 6H), 7.69 (t, J = 7.6 Hz,
1H), 7.82 (s, 1H), 7.92 (d, J = 8.0 Hz, 1H), 8.15 (dd, J = 8.4 Hz, 1.6
8605
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Organometallics
Article
Hz, 1H), 8.45 (dd, J = 4.0 Hz, 1.6 Hz, 1H). 13C NMR (100 MHz,
CDCl3): δ 147.0, 146.5, 146.3, 141.8, 139.5, 137.9, 136.8, 134.4, 133.5,
131.4, 129.9, 129.3, 128.6, 128.5, 128.3, 127.8, 127.6, 127.3, 127.1,
126.4, 126.3, 125.9, 120.8, 21.5. IR (KBr): ν 3053, 1600, 1574, 1514,
1487, 1386, 1261, 1164, 1073, 1015, 909, 804, 780, 732, 720 cm−1.
HRMS (ESI) m/z: 346.1599 [M + H+] (calcd 346.1517). Anal. Found
(calcd) for C26H19N: C, 90.43 (90.40); H, 5.59 (5.54); N, 4.05 (4.05).
10-(3,4-Difluorophenyl)-5-phenylbenzo[h]quinoline (3cl): white
332.1361). Anal. Found (calcd) for C25H17N: C, 90.71 (90.60); H,
5.20 (5.17); N, 4.23 (4.23).
ASSOCIATED CONTENT
* Supporting Information
■
S
1H NMR, 13C NMR, and 19F NMR spectra of all the new
compounds, computational details, and CIF files including X-
ray crystallographic data for the structure of (Ph3P)2Rh(CO)Cl.
This material is available free of charge via the Internet at
http://pubs.acs.org.
1
solid (yield: 80%). H NMR (400 MHz, CDCl3): δ 7.09−7.12 (m,
1H), 7.18−7.25 (m, 2H), 7.32 (dd, J = 8.4 Hz, 4.4 Hz, 1H), 7.50−7.57
(m, 6H), 7.72 (t, J = 7.6 Hz, 1H), 7.85 (s, 1H), 7.95−7.98 (m, 1H),
8.19 (dd, J = 8.4 Hz, 1.6 Hz, 1H), 8.05 (dd, J = 4.0 Hz, 1.6 Hz, 1H).
1
13C NMR (100 MHz, CDCl3): δ 149.7 (dd, JC−F = 244.2 Hz, 12.8
AUTHOR INFORMATION
Corresponding Author
*E-mail: wjh@tju.edu.cn.
1
3
■
Hz), 149.0 (dd, JC−F = 243.9 Hz, 12.5 Hz), 146.6, 143.3 (dd, JC−F
=
16.0 Hz, 4.3 Hz), 139.4, 139.3, 138.2, 134.4, 133.7, 131.1, 129.9, 128.6,
128.5, 128.4, 128.2, 127.8, 127.3, 126.5, 124.5 (dd, 3JC−F = 15.9 Hz, 3.4
Hz), 121.0, 117.8 (d, 2JC−F = 17.2 Hz), 116.0 (d, 2JC−F = 17.1 Hz). 19
F
Notes
NMR (376 MHz, CDCl3): δ −140.3 (m, 1F), −143.0 (m, 1F). IR
(KBr): ν 3057, 1603, 1519, 1415, 1331, 1264, 1198, 1115, 1015, 976,
916, 868, 805, 703 cm−1. HRMS (ESI) m/z: 368.1287 [M + H+]
(calcd 368.1173). Anal. Found (calcd) for C25H15F2N: C, 81.77
(81.73); H, 4.15 (4.12); N, 3.80 (3.81).
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by grants from the NSFC (21072149,
20872108, 20872109) and the Innovation Foundation of
Tianjin University.
5-(4-Fluorophenyl)-10-(m-tolyl)benzo[h]quinoline (3da): white
1
solid (yield: 48%). H NMR (400 MHz, CDCl3): δ 2.41 (s, 3H),
7.17−7.31 (m, 7H), 7.48−7.52 (m, 2H), 7.57 (dd, J = 7.2 Hz, 1.2 Hz,
1H), 7.69 (t, J = 7.6 Hz, 1H), 7.78 (s, 1H), 7.90 (dd, J = 7.6 Hz, 0.8
Hz, 1H), 8.08 (dd, J = 8.0 Hz, 1.6 Hz, 1H), 8.43 (dd, J = 4.0 Hz, 1.6
REFERENCES
■
1
Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 162.5 (d, JC−F = 245.5
(1) For recent reviews on C−C activation, see: (a) Jennings, P. W.;
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Hz), 147.1, 146.6, 146.2, 141.8, 136.7, 135.4 (d, 3JC−F = 3.0 Hz), 134.3,
2
133.2, 131.6, 131.5, 129.2, 128.5, 127.8, 127.2 (d, JC−F = 18.9 Hz),
2
126.3, 125.9, 120.8, 115.4 (d, JC−F = 21.3 Hz), 21.5. 19F NMR (376
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1224, 1158, 910, 837, 778, 733 cm−1. HRMS (ESI) m/z: 364.1480 [M
+ H+] (calcd 364.1423). Anal. Found (calcd) for C26H18FN: C, 85.99
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(3el): white solid (yield: 89%). 1H NMR (400 MHz, CDCl3): δ 7.10−
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7.56 (d, J = 7.2 Hz, 1H), 7.58−7.62 (m, 2H), 7.67 (dd, J = 8.4 Hz, 1.6
Hz, 1H), 7.73 (t, J = 7.6 Hz, 1H), 7.94−8.04 (m, 6H), 8.22 (dd, J = 8.4
Hz, 1.6 Hz, 1H), 8.51 (dd, J = 4.0 Hz, 1.6 Hz, 1H). 13C NMR (100
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1
MHz, CDCl3): δ 149.7 (dd, JC−F = 243.7 Hz, 12.7 Hz), 149.0 (dd,
1JC−F = 243.5 Hz, 13.0 Hz), 146.7, 143.3 (dd, 3JC−F = 6.0 Hz, 4.5 Hz),
139.5, 138.2, 136.8, 134.4, 133.7, 133.4, 132.8, 131.2, 128.8, 128.6,
3
128.5, 128.1, 128.0, 127.8, 127.3, 126.6, 126.5, 126.3, 124.4 (dd, JC−F
= 5.6 Hz, 3.5 Hz), 121.1, 117.8 (d, 2JC−F = 17.3 Hz), 116.0 (d, 2JC−F
=
16.5 Hz). 19F NMR (376 MHz, CDCl3): δ −140.3 (m, 1F), −143.0
(m, 1F). IR (KBr): ν 3055, 1601, 1519, 1449, 1415, 1388, 1264, 1198,
1114, 860, 804, 736 cm−1. HRMS (ESI) m/z: 418.1331 [M + H+]
(calcd 418.1329). Anal. Found (calcd) for C29H17F2N: C, 83.51
(83.44); H, 4.15 (4.10); N, 3.37 (3.36).
7-Methoxy-10-phenylbenzo[h]quinoline (3fa): white solid (yield:
1
95%). H NMR (400 MHz, CDCl3): δ 4.09 (s, 3H), 7.12 (d, J = 8.0
Hz, 1H), 7.30−7.41 (m, 6H), 7.48 (d, J = 8.0 Hz, 1H), 7.70 (d, J = 8.8
Hz, 1H), 8.09 (dd, J = 8.0 Hz, 1.6 Hz, 1H), 8.39−8.42 (m, 2H). 13C
NMR (100 MHz, CDCl3): δ 154.8, 146.7, 146.6, 146.5, 135.0, 133.8,
131.3, 129.9, 128.9, 127.4, 127.2, 125.7, 125.3, 125.0, 121.5, 121.1,
106.5, 55.8. IR (KBr): ν 3050, 1589, 1509, 1451, 1418, 1317, 1243,
1111, 1070, 1023, 833, 811, 763, 734, 713, 697 cm−1. HRMS (ESI) m/
z: 286.1228 [M + H+] (calcd 286.1154). Anal. Found (calcd) for
C20H15NO: C, 84.23(84.19); H, 5.35 (5.30); N, 4.91 (4.91).
7,10-Diphenylbenzo[h]quinoline (3ga): white solid (yield: 93%).
1H NMR (400 MHz, CDCl3): δ 7.33 (dd, J = 8.0 Hz, 4.4 Hz, 1H),
7.36−7.43 (m, 5H), 7.48−7.50 (m, 1H), 7.52−7.56 (m, 4H), 7.59−
7.65 (m, 3H), 7.94 (d, J = 8.8 Hz, 1H), 8.07 (d, J = 8.0 Hz, 1H), 8.44
(dd, J = 4.0 Hz, 1.6 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 146.9,
146.8, 146.7, 141.1, 141.0, 140.0, 134.9, 132.7, 130.8, 130.3, 129.4,
128.6, 128.4, 128.3, 127.4, 127.3, 126.8, 125.9, 125.6, 125.5, 121.2. IR
(KBr): ν 3053, 3027, 1600, 1502, 1444, 1419, 1406, 1265, 835, 759,
739, 700 cm−1. HRMS (ESI) m/z: 332.1439 [M + H+] (calcd
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