Efficient Rh(I)-Catalyzed direct arylation and alkenylation of arene C-H bonds via decarbonylation of benzoic and cinnamic anhydrides

Article abstract of DOI:10.1021/ol9000729

Efficient rhodium(I)-catalyzed regioselective direct arylation and alkenylation of aromatic C-H bonds has been realized with aromatic carboxylic and cinnamic anhydrides as the coupling partners via decarbonylation and C-H activation under phosphine-free c

Full text of DOI:10.1021/ol9000729

ORGANIC
LETTERS
2009
Vol. 11, No. 6
1317-1320
Efficient Rh(I)-Catalyzed Direct Arylation
and Alkenylation of Arene C-H Bonds
via Decarbonylation of Benzoic and
Cinnamic Anhydrides
Weiwei Jin,†,‡ Zhengkun Yu,*,† Wei He,† Wenjing Ye,† and Wen-Jing Xiao‡
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan
Road, Dalian, Liaoning 116023, P. R. China, and Key Laboratory of Pesticide &
Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal
UniVersity, Wuhan, Hubei 430079, P. R.China
zkyu@dicp.ac.cn
Received January 17, 2009
ABSTRACT
Efficient rhodium(I)-catalyzed regioselective direct arylation and alkenylation of aromatic C-H bonds has been realized with aromatic carboxylic
and cinnamic anhydrides as the coupling partners via decarbonylation and C-H activation under phosphine-free conditions.
Transition-metal-catalyzed functionalization of arene C-H
bonds has recently been paid much attention.1 ortho-
Arylation, alkenylation, and alkylation of sp2C-H bonds
involving subsequent regioselective formation of new C-C
or C-X bonds assisted by various directing groups under
palladium,2 rhodium,3 ruthenium,4 copper,5 nickel,6 and iron7
catalysis have attracted rapidly growing interest. Arenes and
heterocycles usually undergo chelation-assisted C-H func-
tionalization with organic or organometallic coupling partners
such as aromatic halides,2c,3-5,8 sulfonate esters,4c,9 boronic
acids,7a,10 alkynes,3c,5c,6 olefins,11 alkyl acrylates,12 arenes,13
cycloalkanes,14 arylsilanes,15 organotrifluoroborates,16 or-
ganotin,17 and arylzinc7b reagents, producing the cross-
coupling products. Peroxides,18a diethyl azodicarboxylate,18b,c
arenediazonium salts,18d PhIdNNs,18e aldehydes,18f di-tert-
butyldiaziridinone,18g epoxides,18h and unactivated aromatic
† Dalian Institute of Chemical Physics.
‡ Central China Normal University.
(1) For recent reviews, see: Alberico, D.; Scott, M. E.; Lautens, M.
Chem. ReV. 2007, 107, 174.
(2) For selected recent reports on palladium catalysis, see: (a) Giri, R.;
Yu, J.-Q. J. Am. Chem. Soc. 2008, 130, 14082. (b) Wasa, M.; Yu, J.-Q.
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Khan, R. M. K.; Daugulis, O. J. Am. Chem. Soc. 2008, 130, 15185. (b) Do,
H.-Q.; Daugulis, O. J. Am. Chem. Soc. 2008, 130, 1128. (c) Sun, Z. K.;
Yu, S. Y.; Ding, Z. D.; Ma, D. W. J. Am. Chem. Soc. 2007, 129, 9300.
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Nakao, Y.; Hiyama, T. Angew. Chem., Int. Ed. 2007, 46, 8872. (b) Nakao,
Y.; Kanyiva, K. S.; Hiyama, T. J. Am. Chem. Soc. 2008, 130, 2448.
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Soc. 2008, 130, 5858.
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A. M.; Lewis, J. C.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc.
2008, 130, 14926. (b) Lewis, J. C.; Berman, A. M.; Bergman, R. G.; Ellman,
J. A. J. Am. Chem. Soc. 2008, 130, 2493. (c) Li, L.; Brennessel, W. W.;
Jones, W. D. J. Am. Chem. Soc. 2008, 130, 12414.
(4) For selected recent reports on ruthenium catalysis, see: (a) Ozdemir,
I.; Demir, S.; Cetinkaya, B.; Gourlaouen, C.; Maseras, F.; Bruneau, C.;
Dixneuf, P. H. J. Am. Chem. Soc. 2008, 130, 1156. (b) Ackermann, L.;
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Born, R.; Alvarez-Bercedo, P. Angew. Chem., Int. Ed. 2007, 46, 6364. (c)
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Fagnou, K. J. Am. Chem. Soc. 2008, 130, 3266. (b) Larive´e, A.; Mousseau,
J. J.; Charette, A. B. J. Am. Chem. Soc. 2008, 130, 52. (c) Lu, J. M.; Tan,
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10.1021/ol9000729 CCC: $40.75
Published on Web 02/17/2009
2009 American Chemical Society

Table 1. Screening of Reaction Conditionsa
entry
cat./mol %
additive
base
T (°C)
time (h)
conversionb (%)
1
2
3
4
5
6
7
8
[Rh(COD)Cl]2/5
[Rh(COD)Cl]2/5
[Rh(COD)Cl]2/2.5
[Rh(COD)Cl]2/1
[Rh(COD)Cl]2/2.5
[Rh(COD)Cl]2/2.5
[Rh(COD)Cl]2/5
[Rh(COD)Cl]2/2.5
[Rh(COD)Cl]2/2.5
[Rh(COD)Cl]2/2.5
[Rh(CO)2Cl]2/2.5
[Rh(CO)2Cl]2/5
Rh(COD)2BF4/2.5
Rh(COD)2BF4/5
RhCl(PPh3)3/5
[Rh(COD)Cl]2/2.5
Pd(OAc)2/2.5
MS
MS
MS
MS
MS
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
K3PO4
145
145
145
145
130
145
145
145
145
145
145
145
145
145
145
145
145
16
6
9
9
9
9
13
9
9
9
9
16
9
16
16
9
100 (92)c
>99 (93)c
>99 (92)c
85
90
70
97
>99
97
64
88
100
87
MS
MS
MS
MS
MS
MS
MS
MS
MS
MS
9
KF
K2CO3
10
11
12
13
14
15
16d
17e
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
98
8
10
0
9
a Conditions: 1, 0.5 mmol; 2a, 1.5 equiv; base, 2 equiv; MS ) 4A molecular sieves, 0.600 g; o-xylene, 3 mL. b Conversion of 1 determined by GC
analysis. c Isolated yield of 3a in parentheses. d 20 mol % of PPh3 was added. e 1,4-Benzoquinone (1.0 equiv) was added.
rings2c,19 were also reported for this purpose. Although a
variety of coupling partners were successfully explored, they
have been applied in C-H functionalization with limited
generality.1,20 Very recently, we reported Rh(I)-catalyzed
decarbonylative C-H functionalization by using acid chlo-
rides as the coupling partners.21 More recently, we found
that benzoic anhydrides, as the coupling partners for Rh(I)-
catalyzed aromatic C-H activation, are much more efficient
than their benzoyl chloride analogues. Anhydrides are usually
cheap and can be readily derived from their mother acids.
Carboxylic acids can be decarbonylatively transformed by
transition metals,22 but only scattered examples have been
documented.23 Herein, we report [Rh(COD)Cl]2-catalyzed
direct arylation and alkenylation of arene C-H bonds via
decarbonylation of benzoic and cinnamic anhydrides.
First, we carried out the reactions of benzo[h]quinoline
(1) with benzoic anhydride (2a) under the typical Rh(I)
catalysis conditions for decarbonylative arylation of 1 with
benzoyl chlorides.21 The [Rh(COD)Cl]2-catalyzed reaction
of 1 with 2a efficiently afforded the desired arylation product
3a in 92% isolated yield via decarbonylation of 2a (Table
1, entry 1). Within 6 h, the reaction was also complete to
give 3a in a decent yield (93%, entry 2), suggesting that the
present catalytic system is more efficient than that using
benzoyl chloride for the same purpose. Lowering the catalyst
amount to 2.5 mol %, the reaction also proceeded efficiently
(entry 3). Further lowering the catalyst to 1 mol % or
decreasing the reaction temperature to 130 °C (entries 4 and
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J. Am. Chem. Soc. 2008, 130, 9613. (b) Shi, Z. J.; He, C. J. Am. Chem.
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N.; Zhang, Y.-H.; Yu, J.-Q. Angew. Chem., Int. Ed. 2008, 47, 4882. (c)
Yang, S.-D.; Sun, C.-L.; Fang, Z.; Li, B.-J.; Li, Y.-Z.; Shi, Z. J. Angew.
Chem., Int. Ed. 2008, 47, 1473. (d) Vogler, T.; Studer, A. Org. Lett. 2008,
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Kakiuchi, F. J. Am. Chem. Soc. 2007, 129, 9858. (d) Lewis, J. C.; Bergman,
R. G.; Ellman, J. A. J. Am. Chem. Soc. 2007, 129, 5332
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Ed. 2008, 47, 3004. (c) Cai, G. X.; Fu, Y.; Li, Y. Z.; Wan, X. B.; Shi, Z. J.
J. Am. Chem. Soc. 2007, 129, 7666. (d) Zaitsev, V. G.; Daugulis, O. J. Am.
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130, 2900. (b) Yu, W.-Y.; Sit, W. N.; Lai, K.-M.; Zhou, Z. Y.; Chan,
A. S. C. J. Am. Chem. Soc. 2008, 130, 3304. (c) Xu, X. L.; Li, X. N.; Ma,
L.; Ye, N.; Weng, B. J. J. Am. Chem. Soc. 2008, 130, 14048. (d) Wetzel,
A.; Ehrhardt, V.; Heinrich, M. R. Angew. Chem., Int. Ed. 2008, 47, 9130.
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2007, 129, 12058. (f) Kuninobu, Y.; Nishina, Y.; Takeuchi, T.; Takai, K.
Angew. Chem., Int. Ed. 2007, 46, 6518. (g) Zhao, B. G.; Du, H. F.; Shi,
Y. A. J. Am. Chem. Soc. 2008, 130, 7220. (h) Shi, Z. J.; He, C. J. Am.
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Angew. Chem., Int. Ed. 2008, 47, 1115. (c) Hull, K. L.; Sanford, M. S.
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1318
Org. Lett., Vol. 11, No. 6, 2009

5) led to incomplete conversion of 1. Surprisingly, in contrast
to the Rh(I)/benzoyl chloride system,21 the present catalytic
system worked well without molecular sieves, achieving 97%
conversion for 1 with 5 mol % catalyst over a period of 13 h
(entries 6 and 7), but it is obvious that 4A molecular sieves
improved the transformation (entries 1-7). K3PO4 and KF
also worked efficiently as the bases, while K2CO3 was less
effective (entries 8-10). Both [Rh(CO)2Cl]2 and Rh(COD)2-
BF4 can be used as the catalysts with a 5 mol % loading
(entries 11-14). However, Wilkinson’s catalyst RhCl(PPh3)3
only showed poor catalytic activity, which is similar to the
result obtained in the presence of PPh3 (entries 15 and 16).
Pd(OAc)2 did not effect the arylation reaction (entry 17),
although palladium can catalyze the decarbonylative reactions
of aroyl chlorides.24 The reaction conditions were thus
optimized as shown for entry 3: 2.5 mol % of [Rh(COD)Cl]2
as the catalyst, Na2CO3 as the base, and 4A MS as the
promoter in refluxing o-xylene for 9 h.
produced products 3f-i in 40-66% yields, but increasing
the catalyst loading to 5 mol % and/or extending the reaction
time to 12-24 h gave the same products in 74-97% yields,
respectively (entries 6-9). The reaction of 1 with 4-nitroben-
zoic anhydride (2j) was complicated, affording product 3j
in 23% yield (entry 10), and no desired product was isolated
from the reaction of 1 and 3-nitrobenzoic anhydride.
However, the reaction of 1 with 3-nitro-4-methylbenzoic
anhydride (2k) produced product 3k in 72% yield (entry 11),
revealing that an electron-donating substituent in anhydride
2 facilitates the arylation reaction.
Unexpectedly, thiophene-2-carboxylic anhydride (2l) and
furoic anhydride (2m) also underwent the direct decarbo-
nylative arylation with 1, forming 3l and 3m in 64% and
57% yields, respectively (entries 12 and 13). Surprisingly,
cinnamic anhydride (2n) underwent the same type of reaction
to form the direct alkenylation product 3n in 82% yield (entry
14). It should be noted that the reactions of 1 with 2-chloro-,
2-bromo-, and 2-methylbenzoic anhydrides did not take place
due to the ortho-steric hindrance from the substituents.
The reactions of 1 with other carboxylic anhydrides were
then carried out to define the protocol scope (Table 2). When
N-Heteroaromatic substrates were also applied to explore
the generality of the direct arylation and alkenylation method.
The reaction of 2-phenylpyridine (4a) with 2a was chosen
as the model reaction to optimize the reaction conditions.
Using 5.0-7.5 mol % of [Rh(COD)Cl]2 as the catalyst, >1.0
equiv of 2a as the coupling partner, Na2CO3 as the base,
and 4A MS as the promoter in refluxing o-xylene, >99%
conversion was obtained for 4a, forming a mixture of mono-
and double arylation products. Both increasing the molar ratio
of 2a to 4a and extending the reaction time favored forma-
tion of the double arylation product 5a. Eventually, the
reaction of 4a (0.5 mmol) with 2a (3 equiv) was carried out
using 5 mol % catalyst, 4 equiv of Na2CO3, and 4A MS in
refluxing o-xylene at 145 °C for 12 h, affording a mixture
of the mono- and double-arylation products (1:99) with
>99% conversion for 4a. The desired double-arylation
product 5a was then isolated in 79% yield (Table 3, entry
1). For 2-pyridine-substituted arenes 4b-f, their direct
arylation with 2a gave the desired products 5b-f in 57-78%
yields (entries 2-6). For 2-benzoylpyridine 4g and N-
heterocycle 4h (entries 7 and 8), they were also efficiently
arylated by 2a to form 5g (86%) and 5h (64%), respectively,
as compared to the reported results (33-34% yields) by using
Rh(I)/benzoyl chloride.21 A reactivity order of oxidative
addition to Pd(0) has been established: PhI . (PhCO)2O >
PhOTf > PhBr,25 which suggests that (PhCO)2O is a more
reactive coupling reagent than PhOTf and PhBr. Thus,
anhydrides (ArCO)2O may be used as the more capable
coupling partners than ArBr in C-H functionalization. With
cinnamic anhydride (2n) as the coupling partner, the reactions
of 4a-h efficiently produced the alkenylation products 6a-h
in 64-97% yields (entries 9-16), suggesting a promising
alternative to compounds of type 6 instead from Heck
reactions of aryl halides and styrene.26 Alkenylation of arenes
and N-heterocycles via C-H bond activation usually utilize
alkynes,6 olefins,11 and alkyl acrylates12 as the coupling
reagents.
Table 2. Direct Arylation of 1 via Decarbonylation of 2 and
C-H Bond Activationa
entry
R
2
product
yieldb (%)
1
2
3
4
5
6
7
8
Ph
4-MeC6H4
3-MeC6H4
3,4-Me2C6H3
3,5-Me2C6H3
4-ClC6H4
3-ClC6H4
4-BrC6H4
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
92
97
75
95
81
62 (97)c
62 (76)c
66 (76)d
40 (74)e
23e
9
3-BrC6H4
10
11
12
13
14
4-NO2C6H4
3-NO2-4-MeC6H3
2-thiophenyl
2-furanyl
72
64e
57e
C6H5CHdCH
60 (82)d
a Conditions: 1, 0.5 mmol; 2, 1.5 equiv; [Rh(COD)Cl]2, 2.5 mol %;
Na2CO3, 2 eq; MS, 0.600 g; o-xylene, 3 mL; 145 °C, 9 h. b Isolated yields.
c 24 h. d 5.0 mol % of catalyst, 12 h. e 5.0 mol % catalyst, 24 h.
methyl-substituted benzoic anhydrides (2b-e) were used as
the coupling partners, the products 3b-e were obtained in
decent yields (75-97%, entries 2-5). The reactions of 1
with 4- and 3-chloro- or -bromobenzoic anhydrides 2f-i
(23) (a) Goossen, L. J.; Rodríguez, N. Chem. Commun. 2004, 724. (b)
Chatani, N.; Tatamidani, H.; Ie, Y.; Kakiuchi, F.; Murai, S. J. Am. Chem.
Soc. 2001, 123, 4849. (c) Jobashi, T.; Hino, T.; Maeyama, K.; Ozaki, H.;
Ogino, K.; Yonezawa, N. Chem. Lett. 2005, 34, 860. (d) Goossen, L. J.;
Paetzold, J.; Winkel, L. Synlett 2002, 1721. (e) Goossen, L. J.; Paetzold, J.
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115, 10414.
To investigate the reactivity of the substrates and coupling
partners further, three competition reactions were explored
Org. Lett., Vol. 11, No. 6, 2009
1319

4f, producing 3a as the major product in the reaction of 1/4f
(1:1) with 2a (eq 5).
Table 3. Direct Arylation of 2-Arylpyridines (4) via
Decarbonylation of 2a or 2n and C-H Bond Activationa
A possible mechanism is proposed in Scheme 1. Anhy-
dride 2 is oxidatively added to the Rh(I) species to form an
Scheme 1. Proposed Mechanism
aroylcarboxylate metal complex [RCORh(III)Cl (OCOR)] (7)
which undergoes decarbonylation to form aryl carboxyl-
ate-Rh(III) (8). Intermediate 8 reacts with arene 1 to
generate complex 9 by C-H bond activation via intramo-
lecular ortho-chelating assistance in the presence of Na2CO3
base. The desired product 3 is then produced via the reductive
elimination of 9. This proton abstraction mechanism is
plausible to explain functionalization of the aromatic C-H
bonds by carboxylic anhydrides.4a,27
In summary, efficient regioselective direct arylation and
alkenylation of aromatic C-H bonds has been realized by
Rh(I) catalysis using aromatic carboxylic and cinnamic
anhydrides as the coupling partners via decarbonylative C-H
bond activation with arene or N-heteroaromatic substrates
under phosphine-free conditions. The present catalytic system
is much more efficient than the Rh(I)/aroyl chloride system21
for the same purpose.
a Conditions: 4, 0.5 mmol; [Rh(COD)Cl]2, 5 mol %; MS, 0.600 g;
o-xylene, 3 mL; 145 °C, 12 h. (A) 2a or 2n, 3.0 equiv; Na2CO3, 4 eq. (B)
2a or 2n, 1.5 equiv; Na2CO3, 2 equiv. b Isolated yields. c GC yield (100%
conversion for 4d, a mixture of 33:67 di- and monoarylation products was
obtained). d 16 h.
under the typical conditions as shown in Tables 2 and 3 (eqs
3-5). A 1:1 molar ratio mixture of 2a and 2b was reacted
with 1, affording the arylation products 3a and 3b in a 45:
55 molar ratio (eq 3), which further demonstrates that an
electron-donating substituent in the anhydride favors the
arylation. Under the same conditions, using benzoyl chloride
instead of benzoic anhydride 2a led to less of 3a (eq 4),
revealing that benzoyl chloride is less reactive than benzoic
anhydride in the Rh(I)-catalyzed decarbonylative arylation
of 1. Arene 1 exhibited a higher reactivity than 2-arylpyridine
Acknowledgment. We are grateful to the National Natural
Science Foundation of China (20772124) and the National
Basic Research Program of China (2009CB825300) for
support of this research.
Supporting Information Available: Experimental pro-
cedures, analytical data, and copies of NMR spectra. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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OL9000729
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