Silver(i)-catalyzed carboxylation of arylboronic esters with CO2

Article abstract of DOI:10.1039/c2cc32045b

A variety of arylboronic esters were efficiently carboxylated with CO ₂ using a simple AgOAc/PPh₃ catalyst, affording the corresponding carboxylic acids in good yield. This simple and efficient silver(i) catalytic system showed wide functional group compatibility. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2cc32045b

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Silver(I)-catalyzed carboxylation of arylboronic esters with CO2†
Xiao Zhang, Wen-Zhen Zhang,* Ling-Long Shi, Chun-Xiao Guo, Ling-Ling Zhang and Xiao-Bing Lu*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Given that CO2 could insert into the sp2ꢀhybridized carbon–
5
A variety of arylboronic esters were efficiently carboxylated
50 silver bond to afford silver carboxylate, silver would be
another metal candidate which shows expectant activity
toward the carboxylation of arylboronic reagents with CO2.13
Indeed, in our recently developed silver(I)ꢀcatalyzed
carboxylation of terminal alkynes with CO2,7g the insertion of
55 CO2 into spꢀhybridized carbon–silver bond can be easily
achieved. This result leads us to ask the following question:
does the smooth performance also occur in the insertion of
CO2 into sp2ꢀhybridized carbon–silver bond? On the basis of
above mechanistic and experimental insights, we envisioned
60 that with wise choice of ligand and base, silver complexes
could be promising catalysts for the carboxylation of
arylboronic esters with CO2 (Scheme 1). Herein, we report the
with CO2 using a simple AgOAc/PPh3 catalyst, affording the
corresponding carboxylic acids in good yield. This simple and
efficient silver(I) catalytic system showed wide functional
group compatibility.
10 The incorporation of CO2 into organic substrates to provide
high valueꢀadded chemicals has gained much attention, since
CO2 is an abundant, inexpensive, and renewable carbon
resource.1 In the presence of a suitable transitionꢀmetal
catalyst, various carbon nucleophiles including organotin,2
15 organoboron3 and organozinc reagents,4,5 unsaturated
compounds,6 terminal alkynes,7 and activated C–H bonds8 can
be successfully carboxylated into carboxylic acids and
derivatives9 using CO2 as carboxylative reagent. Among these
nucleophiles, organoboronic acids and their derivatives are
20 particularly attractive substrates due to their ease of handling,
broad availability and functional group compatibility.10,11 In
2006, Iwasawa and coworker reported that the carboxylation
of arylꢀ and alkenylboronic esters could be smoothly carried
out using [Rh(OH)(cod)]2/dppp as catalyst and 3 equivalents
25 of CsF as base.3a However, the rhodium catalytic system was
proven to be inert toward bromo, nitro, alkynyl and vinyl
substitutated organoboronic esters. This limitation was
subsequently overcome by using CuI/bisoxazoline ligands
catalytic system discovered by same group3b and Nꢀ
30 heterocyclic carbene copper(I) catalysts developed by Hou et
al.3c These copper(I) catalytic systems showed much higher
chemoselectivity and wider substrate scope, epoxide, aldehyde
groups were also tolerated.
realization of this hypothesis, in which
a variety of
arylboronic esters were efficiently carboxylated with CO2
65 using a simple and efficient silver(I)ꢀbased catalyst. This
catalytic system showed wide substrate scopes and various
functionalized carboxylic acids could be obtained in good
yield.
R
B(OR')2
Base
R
M'
COO
R
[M]
COO
R
[M]
M = Rh, Cu
I
II
CO2
Transmetalation from boron to silver
was previously reported by Ritter, Jarvo
Ar
B(OR')2
Base
Ar
COOM'
With regard to the mechanism of rhodiumꢀ or copperꢀ
35 catalyzed carboxylation of organoboronic esters with CO2
(Scheme 1), active species I bearing a new metal–carbon bond
was initially formed by transmetalation reaction of metal
catalyst with organoboronic ester, subsequent insertion of CO2
into metal–carbon bond afforded metal carboxylate II, which
40 further underwent one or two transmetalation reaction
Ar
[Ag]
COO
Ar [Ag]
CO2
???
Insertion of Csp Ag bond with CO2
was previously reported by us
regenerating
I
and simultaneously forming the new
70
Scheme 1 Transitionꢀmetalꢀcatalyzed carboxylation of organoboronic
esters with CO2
carboxylate product. It is wellꢀknown that besides rhodium
and copper catalyst, silver complexes can also serve as
effective catalysts for the reaction using allenylꢀ and
45 arylboronic acids or esters as nucleophiles. In this reaction,
transmetalation from boron to silver can easily proceed in the
presence of suitable base, thus highly reactive species bearing
sp2ꢀhybridized carbon–silver bond is thought to be formed.12
Initially,
the
carboxylation
reaction
of
4ꢀ
methoxyphenylboronic acid 2,2ꢀdimethylꢀ1,3ꢀpropanediol
ester (1a) with CO2 was chosen as a model reaction to screen
75 the optimized silver catalytic system (Table 1). A poor (25%)
but encouraging yield of 4ꢀmethoxybenzoic acid (2a) was
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obtained using 10 mol % AgOAc alone as catalyst and 2 equiv
of KOtBu as base (Table 1, entry 1). To our surprise, the
addition of a simple PPh3 ligand resulted in a remarkable
obtained (Entry 14). Potassium carbonate was found to be
unsuitable base for this reaction system (Entry 15). The
decreased catalyst loading (5 mol % Ag) resulted in a slightly
increase in yield (91%) of 2a (Entry 2). It is noteworthy that 35 lower yield of product (Entry 17). Notably, 1 mol % loading
5
no carboxylative product was observed in the absence of any
transitionꢀmetal catalyst (Entry 3). In the further ligand
screening, more bulky PCy3 ligand gave 85% yield (Entry 4),
while strikingly decreased yield was observed for the
of silver catalyst at 100 oC gave good yield of 2a in the
shorter time (Entries 18 and 19). The silver catalytic system
proved to be sensitive to the CO2 pressure, and relatively high
CO2 pressure (20 atm) is beneficial to enhancing the reaction
bidentate ligand dppe (Entry 5). Compared with cheap and 40 rate (Table 1, entries 2 and 22, entries 19 and 21).
10 readily available PPh3 ligand, Nꢀheterocyclic carbene ligands,
which were obtained by multistep synthesis, also gave lower
yield (Entries 6–9).
Table 2 AgOAc/PPh3ꢀcatalyzed carboxylation of various organoboronic
esters with CO2
Table 1 Silver(I)ꢀcatalyzed carboxylation of organoboronic ester 1a with
a
CO2
Yield (%)a
Method Ab
Entry
Ar
Method Bc
89 (2a)
83 (2b)
75 (2c)
86 (2d)
82 (2e)
86 (2f)
82 (2g)
88 (2h)
84 (2i)
83 (2j)
71 (2k)
76 (2l)
84 (2m)
79 (2n)
74 (2o)
75 (2p)
77 (2q)
79 (2r)
80 (2s)
76 (2t)
75 (2u)
78 (2v)
81 (2w)
83 (2x)
72 (2y)
65 (2z)
61 (3a)
82 (3b)
80 (3c)
1
4ꢀMeOC6H4
3ꢀMeOC6H4
4ꢀPhOC6H4
C6H5
91
15
2
85
Entry
1
Ag(I) salt
AgOAc
AgOAc
ꢀ
Ligand
ꢀ
Base
Yield (%)b
3
75
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
CsF
25
91
ꢀ
4
90
5
4ꢀMeC6H4
4ꢀtBuC6H4
4ꢀFC6H4
83
2
PPh3
PPh3
PCy3
dppe
IMes
SIMes
IPr
6
85
3
7
80
4
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgF
85
35
55
67
87
84
83
86
87
85
30
ꢀ
8
2ꢀClC6H4
89
5
9
3ꢀClC6H4
87
6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
4ꢀClC6H4
84
7
4ꢀBrC6H4
70
8
4ꢀIC6H4
79
9
SIPr
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
2ꢀCF3C6H4
3ꢀCF3C6H4
4ꢀCF3C6H4
3ꢀNO2C6H4
4ꢀCNC6H4
4ꢀ(CH2=CH)C6H4
4ꢀPhC6H4
88
10
11
12
13
14
15
16c
17d
18e
19c.e
20c.f
21c.e.g
22g
73
AgBF4
AgPF6
70
77
AgNO3
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
74
82
K2CO3
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
70
80
85
90
89
57
37
60
1ꢀnaphthyl
2ꢀnaphthyl
2ꢀfuranyl
72
77
83
2ꢀthienyl
84
3ꢀthienyl
80
4ꢀHCOC6H4
4ꢀMeCOC6H4
4ꢀMeOOCC6H4
4ꢀ(PhC≡C)C6H4
76
65
a Reaction conditions: 1a (0.6 mmol), silver(I) salt (0.06 mmol), ligand
(0.09 mmol), base (1.2 mmol), 4 mL THF, 20 atm, 70 oC, 16 h. b Isolated
60
yield. c 1,4ꢀDioxane as solvent. d 5 mol % AgOAc, 7.5 mol % PPh3. e
1
84
mol % AgOAc, 1.5 mol % PPh3, 100 oC, 8 h. f 0.1 mol % AgOAc, 0.15
20 mol % PPh3, 100 oC, 8 h. g 2 atm of CO2. dppe: 1,2ꢀ
bis(diphenylphosphino)ethane. IMes: 1,3ꢀdimesitylꢀimidazolꢀ2ꢀylidene.
SIMes: 1,3ꢀdimesitylꢀimidazolinꢀ2ꢀylidene. IPr: 1,3ꢀbis(2,6ꢀ
diisopropylphenyl)imidazolꢀ2ꢀylidene. SIPr: 1,3ꢀbis(2,6ꢀ
diisopropylphenyl)imidazolinꢀ2ꢀylidene.
81
30
31
80
64
85 (3d)
67 (3e)
25
Combination of PPh3 with other silver sources such as AgF,
AgBF4, AgPF6 or AgNO3 could also serve as effective
catalysts for the carboxylation reaction (Entries 10–13). In the
rhodiumꢀ or copperꢀcatalyzed carboxylation of organoboronic
esters reported by Iwasawa,3a,3b CsF was established as the
a Isolated yield. b Reaction conditions: 1 (0.6 mmol), AgOAc (0.06 mmol),
45 PPh3 (0.09 mmol), KOtBu (1.2 mmol), 4 mL THF, 20 atm, 70 oC, 16 h. c
Reaction conditions: 1 (0.6 mmol), AgOAc (0.006 mmol), PPh3 (0.009
mmol), KOtBu (1.2 mmol), 4 mL 1,4ꢀdioxane, 20 atm, 100 oC, 8 h.
Once established that AgOAc/PPh3 can function as efficient
catalyst for carboxylation of 4ꢀmethoxyphenylboronic esters
50 with CO2, the substrate scope of arylboronic esters was then
30 most efficient base. However, when CsF was used as base in
the AgOAc/PPh3 catalytic system, only 30% yield was
2
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3
For the carboxylation of organoboron reagent with CO2, see: (a) K.
investigated under two optimized reaction conditions: Method
A: 10 mol % AgOAc, 15 mol % PPh3, 2 equiv. KOtBu, THF,
Ukai, M. Aoki, J. Takaya and N. Iwasawa, J. Am. Chem. Soc., 2006,
128, 8706; (b) J. Takaya, S. Tadami, K. Ukai and N. Iwasawa, Org.
Lett., 2008, 10, 2697; (c) T. Ohishi, M. Nishiura and Z. Hou, Angew.
Chem., Int. Ed., 2008, 47, 5792; (d) H. Ohmiya, M. Tanabe and M.
Sawamura, Org. Lett., 2011, 13, 1086; (e) T. Ohishi, L. Zhang, M.
Nishiura and Z. Hou, Angew. Chem., Int. Ed., 2011, 50, 8114; (f) P.
J. Riss, S. Lu, S. Telu, F. I. Aigbirhio and V. W. Pike, Angew.
Chem., Int. Ed., 2012, 51, 2698.
For the carboxylation of organozinc reagents with CO2, see: (a) H.
Ochiai, M. Jang, K. Hirano, H. Yorimitsu and K. Oshima, Org. Lett.,
2008, 10, 2681; (b) C. S. Yeung and V. M. Dong, J. Am. Chem. Soc.,
2008, 130, 7826; (c) K. Kobayashi and Y. Kondo, Org. Lett., 2009,
11, 2035.
o
20 atm, 70 C, 16 h. Method B: 1 mol % AgOAc, 1.5 mol %
65
70
o
PPh3, 2 equiv. KOtBu, 1,4ꢀdioxane, 20 atm, 100 C, 8 h (Table
5
2). These silver(I) catalytic systems showed high level of
generality and a wide range of functional groups were
tolerated, from electronꢀrich aryl ethers (Table 2, entries 1–3,
and 30) to electronꢀwithdrawn aryltrifluoromethyl, arylnitro, ,
4
arylcyano,
arylaldehyde, arylketone and arylester
10 functionalities (Table 2, entries 13–17, 25–27). Chloro and
trifluoromethyl groups at ortho, meta, and para positions were
all compatible with the reaction conditions (Table 2, entries
8–10, and 13–15). Boronic esters with heteroaromatic
derivatives were also found to be suitable substrates (Table 2,
15 entries 22–24, and 31). Notably, similar to copper catalytic
systems, the silver(I) catalytic system proved applicable for
bromo, iodo, nitro, vinyl and alkynyl substituted
organoboronic esters which are inactive toward rhodium
catalytic systems (Table 2, entries 11, 12, 16, 18 and 28).
20 Another advantage of the presented silver(I) catalytic system
is that AgOAc and PPh3 are all inexpensive and commercially
available, which make it more attractive for the potentially
practical applications.
In summary, we report a simple and efficient AgOAc/PPh3
25 catalyst for the carboxylation of arylboronic esters with CO2.
The catalytic system shows wide functional group
compatibility and a variety of functionalized carboxylic acids
can be obtained in good yield. Efforts on the detailed
mechanism and expansion of this silver catalytic system are
30 currently ongoing in our laboratory.
75
5
6
For the direct carboxylation of electrophile with CO2, see: A. Correa
and R. Martin, J. Am. Chem. Soc., 2009, 131, 15974.
For the hydrocarboxylation of unsaturated compounds with CO2, see:
(a) J. Takaya and N. Iwasawa, J. Am. Chem. Soc., 2008, 130, 15254;
(b) C. M. Williams, J. B. Johnson and T. Rovis, J. Am. Chem. Soc.,
2008, 130, 14936; (c) S. Li, W. Yuan and S. Ma, Angew. Chem., Int.
Ed., 2011, 50, 2578; (d) T. Fujihara, T. Xu, K. Semba, J. Terao and
Y. Tsuji, Angew. Chem., Int. Ed., 2011, 50, 523; (e) M. North,
Angew. Chem., Int. Ed., 2009, 48, 4104; (f) Y. Zhang and S. N.
Riduan, Angew. Chem., Int. Ed., 2011, 50, 6210.
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Fukue, S. Oi and Y. Inoue, J. Chem. Soc., Chem. Commun., 1994,
2091; (b) N. Eghbali, J. Eddy and P. T. Anastas, J. Org. Chem.,
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Zhang, Proc. Natl. Acad. Sci. USA, 2010, 107, 20184; (e) W.ꢀZ.
Zhang, W.ꢀJ. Li, X. Zhang, H. Zhou and X.ꢀB. Lu. Org. Lett., 2010,
21, 4748; (f) D. Yu and Y. Zhang, Green Chem., 2011, 13, 1275; (g)
X. Zhang, W.ꢀZ. Zhang, X. Ren, L.ꢀL. Zhang and X.ꢀB. Lu, Org.
Lett., 2011, 13, 2402.
For the carboxylation of C–H bond with CO2, see: (a) I. I. F.
Boogaerts and S. P. Nolan, J. Am. Chem. Soc., 2010, 132, 8858; (b)
L. Zhang, J. Cheng, T. Ohishi and Z. Hou, Angew. Chem., Int. Ed.,
2010, 49, 8670; (c) I. I. F. Boogaerts, G. C. Fortman, M. R. L.
Catherine and S. P. Nolan, Angew. Chem., Int. Ed., 2010, 49, 8674;
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133, 1251; (e) D. M. Dalton and T. Rovis, Nat. Chem., 2010, 2, 710;
(f) I. I. F. Boogaerts and S. P. Nolan, Chem. Commun., 2011, 47,
3021; (g) L. Ackermann, Angew. Chem., Int. Ed., 2011, 50, 3842; (h)
B. J. Flowers, R. GautreauꢀService and P. G. Jessop, Adv. Synth.
Catal., 2008, 350, 2947; (i) O. Vechorkin, N. Hirt and X. Hu, Org.
Lett., 2010, 12, 3567.
80
85
7
90
95
8
This work was financially supported by the National
Natural Science Foundation of China (21172026, U1162101),
the National Basic Research Program of China (973Program:
2009CB825300) and the Fundamental Research Funds for the
35 Central Universities (DUT12LK47).
100
105
Notes and references
State Key Laboratory of Fine Chemicals, Dalian University of
Technology, Dalian, 116012, P. R. China.
9
For reviews, see: L. J. Goossen, N. Rodriguez and K. Goossen,
Angew. Chem., Int. Ed., 2008, 47, 3100.
E-mail: zhangwz@dlut.edu.cn, lxb-1999@163.com;
40 Tel:+86 411 8498 6257, Fax: +86 411 8498 6256
† Electronic Supplementary Information (ESI) available: Experimental
procedures, analytical data and copies of NMR spectra. See
DOI: 10.1039/b000000x/
110 10 For reviews on organoboron reagent, see: (a) N. Miyaura, Bull. Chem.
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A. I. Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy and J. F.
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50
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120
125 13 For examples on silverꢀcatalyzed incorporation of CO2 into other
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2
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Silver(I)-catalyzed carboxylation of arylboronic esters with CO2
Xiao Zhang, Wen-Zhen Zhang,* Ling-Long Shi, Chun-Xiao Guo, Ling-Ling Zhang and Xiao-Bing Lu*
Carboxylation of arylboronic esters with CO2 was achieved using a simple and efficient AgOAc/PPh3 catalyst,
affording various functionalized carboxylic acids in good yield.