Carboxylation of Alkenyl Boronic Acids and Alkenyl Boronic Acid Pinacol Esters with CO2 Catalyzed by Cuprous Halide

Article abstract of DOI:10.1002/ejoc.202000288

A cuprous halide catalysed carboxylation of alkenyl boronic acids and alkenyl boronic acid pinacol esters under CO₂, affording the corresponding α, β-unsaturated carboxylic acids in good yield, has been developed. The potassium (E)-trifluoro(styryl)borate is also compatible with this reaction. This simple and efficient copper(I) catalytic system showed good functional group tolerance.

Full text of DOI:10.1002/ejoc.202000288

European Journal of Organic Chemistry
Accepted Article
Accepted Article
Title: Cuprous halide catalysed carboxylation of alkenyl boronic acids
and alkenyl boronic acid pinacol esters with CO2
Authors: Junting Hong, Onkar S. Nayal, and Fanyang Mo
This manuscript has been accepted after peer review and appears as an
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of the final Version of Record (VoR). This work is currently citable by
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.202000288
Link to VoR: https://doi.org/10.1002/ejoc.202000288
01/2020

10.1002/ejoc.202000288
European Journal of Organic Chemistry
FULL PAPER
Cuprous halide catalysed carboxylation of alkenyl boronic acids
and alkenyl boronic acid pinacol esters with CO2
Junting Hong,[a] Onkar S. Nayal, [a] and Fanyang Mo *[a, b]
[a]
Junting Hong, Onkar S. Nayal, Prof. Dr. Fanyang Mo. Department of Energy and Resources Engineering, College of Engineering, Peking University,
Beijing, 100871, China. Homepage: http://www2.coe.pku.edu.cn/faculty/mofanyang/index.html E-mail: fmo@pku.edu.cn
Prof. Dr. Fanyang Mo. Jiangsu Donghai Silicon Industry S&T Innovation Center, Donghai County, Jiangsu 222300, China.
[b]
Abstract: A cuprous halide catalysed carboxylation of alkenyl boronic
acids and alkenyl boronic acid pinacol esters under CO2, affording the
corresponding α, β-unsaturated carboxylic acids in good yield, has
been developed. The potassium (E)-trifluoro(styryl)borate is also
compatible with this reaction. This simple and efficient copper(I)
catalytic system showed good functional group tolerance.
cuprous halide catalysed system for the carboxylation of three
kinds of alkenyl boron compounds (Scheme 1c), with the
advantage of mild conditions, simple operation, good functional
group compatibility, high yields and external ligand free.
Introduction
Carbon dioxide (CO2) is an ideal carboxylative reagent, and it can
be fixed into organic substrates to provide carboxylic acids and
derivatives.[1] However, CO2 is a less-reactive electrophile, so this
transformation usually required a suitable transition-metal catalyst
and a carbon nucleophile.[1f] Recently, organoboronic acids and
their derivatives have attracted much attention as the carbon
nucleophiles in carboxylation with CO2. The earliest work was the
rhodium-catalysed carboxylation of aryl- and alkenyl boronic
esters with CO2 reported by Iwasawa in 2006.[2] Since then, many
similar
transition
metal
catalysed
carboxylation
of
organoboronates with CO2 have been reported using Cu,[3] Ag,[4]
Ni[5] catalysts. In almost all of these cases, the C(sp2)-B bond was
carboxylated with CO2, except in one case where the alkyl C(sp3)-
B bond was carboxylated with CO2.[3e] In 2010, Lin and Marder[6]
disclosed the DFT studies of the carboxylation reactions of
arylboronate esters with CO2 catalysed by (NHC)Cu(I) complexes,
affirming the basic mechanistic proposal in Hou’s work[3h]
.
In the carboxylation of C(sp2)-B bond with CO2, alkenyl boronic
acid esters are used as substrates, especially alkenyl 5,5-
dimethyl-1,3,2-dioxaborinane (-Bneop),[2, 3g, 3h, 4b, 5] and only two
[3c, 3f]
cases used alkenyl boronic acid pinacol esters (-Bpin)
with
only one example each (Scheme 1a). These two reactions aim to
afford [11C]-labeled carboxylic acids with direct application of
[11C]CO2. And they both proceeded under a micromolar scale,
with copper catalysts, and finished within several minutes.
However, such catalytic systems have the limits of complex
operating conditions, using ligands and additives, trapping
[11C]CO2 below -10 °C, etc. Furthermore, several works[7] on the
synthesis of carboxylic acids from alkenes and terminal alkynes,
involves Cu-catalysed carboxylation of in situ formed related
boron compounds with CO2 (Scheme 1b). However, the
carboxylation of alkenyl boric acid and alkenyl potassium
trifluoroborate with CO2 have not been developed yet.
Scheme 1. a) Previous works: carboxylation of alkenyl boronic acid pinacol
esters with 11CO2; b) Previous Work: synthesis of carboxylic acids from alkenes
and terminal alkynes, involving Cu-catalysed carboxylation of in situ formed
related boron compounds with CO2; c) This Work: carboxylation of alkenyl
boronic acids, boronic acid pinacol esters and potassium (E)-
trifluoro(styryl)borate with CO2.
Results and Discussion
On the basis of our previous work,[3b] we further examined the
carboxylation of alkenyl boric acids and alkenyl boronic acid
pinacol esters to expand the organoboron substrates on the
incorporation of CO2. Herein, we report a simple and efficient
In the optimization study (table 1), we chose (E)-styrylboronic acid
1a as model substrate to react with CO2 at ambient pressure. After
an extensive survey of reaction parameters, we obtained 95%
1
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10.1002/ejoc.202000288
European Journal of Organic Chemistry
FULL PAPER
yield of the desired product by using 3.0 mol% CuCl and 2.0 equiv.
KOMe in DMA at 70 °C for 24 h (entry 1). Other cuprous halides
such as CuI, CuBr were relatively less effective (entries 2-3).
Further study showed that a smaller amount of CuCl was not
conducive to the reaction, and 3 mol% was sufficient (entries 1,
4-5). In addition, the use of other alkoxide bases such as KOtBu,
LiOMe showed less effective (entries 6-7). And 2.0 equiv. is the
optimal stoichiometry of KOMe (entries 1, 8-9). Other solvents
such as DMF, DMSO, MeCN and THF provided low yields of the
desired product (entries 10-13). Furthermore, the reaction
temperature proved to be crucial. Low temperature would
seriously reduce the yield, but it should not either be too high
(entries 1, 14-16). Finally, control experiments show that both the
catalyst and the base are crucial to the reaction (entries 17-18).
Table 1. Optimization of the reaction conditionsa.
Scheme 2. The reaction of (E)-styrylboronic acid 1a, (E)-4,4,5,5-tetramethyl-2-
styryl-1,3,2-dioxaborolane 3a, (E)-trifluoro(styryl)borate 4 with CO2 in the
optimal conditions. a Isolated yield.
Entry
1
Variation from standard conditions
None
Yield (%) b
95
2
CuI instead of CuCl
CuBr instead of CuCl
With 2.0 mol% CuCl
With 4.0 mol% CuCl
KOtBu instead of KOMe
LiOMe instead of KOMe
With 1.5 equiv. KOMe
With 2.5 equiv. KOMe
DMF instead of DMA
DMSO instead of DMA
MeCN instead of DMA
THF instead of DMA
Reaction at room temperature
Reaction at 50 °C
80
3
86
4
79
5
95
6
60
7
80
8
83
9
92
10
11
12
13
14
15
16
17
18
41
34
21
20
trace
48
Reaction at 100 °C
75
Without copper catalyst
Without base
NR
NR
[a] Reaction performed on 1.0 mmol scales. [b] Yields were determined by 1H
NMR with 1,1,2,2-Tetrachloroethane as an internal standard.
While investigating the boron-containing structure in alkenyl
boron compounds, we found that in addition to (E)-styrylboronic
acid 1a, (E)-4,4,5,5-tetramethyl-2-styryl-1,3,2-dioxaborolane 3a
and potassium (E)-trifluoro(styryl)borate 4 also reacted well under
identical conditions (Scheme 2). These three boron compounds
gave the carboxylated product 2a in 92%, 88%, 83% isolated
yields, respectively. We are encouraged that the current method
could be adopted to a broad scope of alkenyl boron compounds,
especially alkenyl boronic acids and alkenyl boronic acid pinacol
esters, since both are commercially available.
Scheme 3. The substrates scope of alkenyl boron acids. Reactions were carried
out by using alkenyl boronic acid 1 (1.0 mmol), cat. CuCl (3.0 mol%), base
KOMe (2.0 equiv.) in DMA at 70 °C for 24 h under 1 atm CO2. Isolated yields
were reported.
We first evaluated the scope of alkenyl boronic acids under the
optimal conditions (Scheme 3). When the substituent R1 was aryl
and R2 was hydrogen, substrates (E)-Styrylboronic acids were
successfully converted to the corresponding cinnamic acids (2a-
2
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10.1002/ejoc.202000288
European Journal of Organic Chemistry
FULL PAPER
h). The p-methyl-substituted styrylboronic acid gave a high yield
(91%, 2b), while p-phenyl-substituted styrylboronic acid and p-
methoxy -substituted styrylboronic acid provided obviously lower
yields (56%, 2c and 64%, 2d), probably because electronic effect
promoted the generation of protodeboronation by-products.
Halogen-substituted styrylboronic acids were compatible and
gave the corresponding products (2e-h) in moderate to good
yields. With the substituent R1 as hydrogen and R2 as aryl, the
substrate (1-phenylvinyl)boronic acid can also gave the desired
product 2m in 82% yield. In addition, cyclic alkenyl substrates
provided the corresponding products (2i and 2l) in good yields.
Also, Boc-protected amines was compatible under the reaction
conditions (2l). Moreover, when R1 was linear alkyl or benzyl, both
the substrates underwent the reaction smoothly (2j and 2k).
containing heterocycle were compatible under the reaction
conditions. Notably, this method is suitable for the synthesis of
many unknown acrylic acids (2p-r, 2t-u).
Based on the previous literatures[3g, 3h, 6, 8] and our own study[3b], a
plausible mechanism was proposed (Scheme 5). On one hand,
previous reports[8] showed very solid evidence that DMA can work
actively as an acido ligand coordinating with copper. On the other
hand, due to stability issue and the empty d orbital of copper,
organocopper species has to be saturated by being coordinated
with substrates, ligands or solvents. As such, the proposed
mechanism circle starts with the complex Cu(DMA)nCl (n = 2 or
3) formed from the coordination between CuCl and DMA. Initially,
the complex Cu(DMA)nCl exchanges the ligand with KOMe to
generate the copper alkoxide Cu(DMA)n(OMe) A, which
undergoes transmetalation with alkenyl boron acid 1 to form the
intermediate B and C. Nucleophilic addition of copper complex C
to CO2 provides copper carboxylate D. -Metathesis with KOMe
generates carboxylic acid potassium salt E and regenerate
Cu(DMA)n(OMe) A, thereby completing the catalytic cycle.
Scheme 4. The substrates scope of alkenyl boronic acid pinacol esters.
Reactions were carried out by using alkenyl boronic acid pinacol ester 3 (1.0
mmol), cat. CuCl (3.0 mol%), base KOMe (2.0 equiv.) in DMA at 70 °C for 24 h
under 1 atm CO2. Isolated yields were reported.
We then focused on the scope of alkenyl boronic acid pinacol
esters (Scheme 4). When the substituent R3 was aryl and R4 was
hydrogen, substrates (E)-Styrylboronic acid pinacol esters
provided the desired products (2a and 2v) in good yields. In
addition, when the substituent R3 was ethoxy carbonyl and R4 was
hydrogen, the substrate gave product 2n in 76% yield. And
product 2n is an important chemical intermediate, monoethyl
fumarate, which can be used to produce preservatives. Again,
cyclic alkenyl substrates gave the corresponding products (2o-u)
in moderate to good yields. Cyclohexenyl boronic acid pinacol
esters afforded products (2o-q, 2s) in high yields, except products
2u, possibly because of the effect of secondary amine and steric
hindrance. Besides, heterocyclehexenyl boronic acid pinacol
esters also provided the desired products (2r, 2l, 2t) in good yields,
implying that both oxygen-containing heterocycle and nitrogen-
Scheme 5. Proposed mechanism.
Conclusion
In summary, we have succeeded in developing the cuprous halide
catalysed carboxylation of alkenyl boronic acids and alkenyl
boronic acid pinacol esters with CO2. The potassium (E)-
trifluoro(styryl)borate can also be carboxylated using this method.
3
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10.1002/ejoc.202000288
European Journal of Organic Chemistry
FULL PAPER
(d, J = 16.0 Hz, 1H). 13C NMR (101 MHz, DMSO-d6) δ 167.99, 164.82,
162.36, 143.15, 131.16 (d, J = 38.4 Hz), 119.55, 116.30 (d, J = 22.2 Hz).[9]
A wide range of alkenyl boron compounds were effetively
transformed into the corresponding α, β-unsaturated carboxylic
acids in moderate to high yield. Good functional group tolerance
improve the generality of the reaction. And the use of inexpensive
cuprous halides, mild conditions and simple operation expand the
utility of the reaction.
(E)-3-fluorocinnamic acid (2f): White solid, 126.2 mg obtained, yield 76%.
Rf: 0.5 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.53 (s, 1H), 7.63
– 7.52 (m, 2H), 7.50 (d, J = 7.8 Hz, 1H), 7.42 (td, J = 7.9, 6.0 Hz, 1H), 7.20
(td, J = 8.5, 2.5 Hz, 1H), 6.60 (d, J = 16.0 Hz, 1H). 13C NMR (101 MHz,
DMSO-d6) δ 167.85, 162.87 (d, J = 244.4 Hz), 142.98 (d, J = 3.0 Hz),
137.24 (d, J = 8.1 Hz), 131.18 (d, J = 8.1 Hz), 124.99 (d, J = 3.0 Hz),
121.28, 117.26 (d, J = 22.2 Hz), 114.79 (d, J = 22.2 Hz).[10]
Experimental Section
(E)-4-chlorocinnamic acid (2g): White solid, 145.6 mg obtained, yield
80%. Rf: 0.6 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.52 (s, 1H),
7.74 (d, J = 8.3 Hz, 2H), 7.61 (d, J = 16.1 Hz, 1H), 7.48 (d, J = 8.2 Hz, 2H),
6.58 (d, J = 16.1 Hz, 1H). 13C NMR (101 MHz, DMSO-d6) δ 167.91, 142.97,
135.18, 133.66, 130.37, 129.36, 120.52.[9]
General information: Solvents were purchased from TONGGUANG
CHEMICAL, Beijing or BEIJING CHEMICAL, in GR (or CCER). Purification
of products was conducted by column chromatography on silica gel (200-
300 mesh, for some cases 300-400 mesh were used, from Qingdao,
China). NMR spectra were measured on a Bruker ARX400 (1H at 400 MHz,
13C at 101 MHz, 19F at 471 MHz) magnetic resonance spectrometer.
Chemical shifts (δ) are reported in ppm using tetramethylsilane as internal
standard (s = singlet, d = doublet, t = triplet, q = quartet, dd = doublet of
doublets, m = multiplet), and coupling constants (J) were reported in Hertz
(Hz). The substrates were purchased from commercial sources.
(E)-4-(trifluoromethyl)cinnamic acid (2h): White solid, 134.0 mg
obtained, yield 62%. Rf: 0.3 (PE/EA=3:1). 51H NMR (400 MHz, DMSO-d6)
δ 12.63 (s, 1H), 7.88 (d, J = 8.0 Hz, 2H), 7.71 (d, J = 8.1 Hz, 2H), 7.66 (d,
J = 16.0 Hz, 1H), 6.67 (d, J = 16.0 Hz, 1H). 13C NMR (101 MHz, DMSO-
d6) δ 167.68, 142.50, 138.69, 130.3 (q, J = 32.3 Hz), 129.20, 126.05 (q, J
= 4.0 Hz), 124.4 (d, J = 272.7 Hz), 122.57.[9]
General experimental procedure for the synthesis of (E)-3-
phenylacrylic acid (2a): Phenylvinylboronic acid 1a (148.0 mg, 1.0 mmol),
KOMe (140.3 mg, 2.0 mmol), CuCl (3.0 mg, 0.03 mmol) was charged in a
50 mL Schlenk tube under N2, followed by 5 mL anhydrous DMA. After that
the Schlenk tube was filled with carbon dioxide by applying four-five cycles
of evacuation and filling with CO2. The Schlenk tube was tightly sealed and
stirred at 70 oC for 24 hours after which it was quenched by careful addition
of 1.0 M aq. HCl sol. The reaction mixture was diluted with water and
extracted three times with EtOAc. The combined organic phases were
washed with brine, dried over anhydrous Na2SO4 and filtered. Then the
solvent was removed in vacuo. The crude product was purified by silica
gel column chromatography (0−25 % EtOAc in pet-ether) to obtain the
desired product 2a 136.2 mg, in 92% yield.
Indene-2-carboxylic acid (2i): White solid, 83.2 mg obtained, yield 52%.
Rf: 0.5 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.51 (s, 1H), 7.69
(s, 1H), 7.62 – 7.52 (m, 2H), 7.38 – 7.32 (m, 2H), 3.63 (s, 2H). 13C NMR
(101 MHz, DMSO-d6) δ 166.16, 145.09, 143.04, 140.61, 138.88, 127.75,
127.22, 124.79, 123.78, 38.56.[9]
(E)-oct-2-enoic acid (2j): Yellow oil, 90.9 mg obtained, yield 64%. Rf: 0.6
(PE/EA=20:1). 1H NMR (400 MHz, DMSO-d6): δ 12.13 (s, 1H), 6.87 – 6.75
(m, 1H), 5.75 (d, J = 15.6 Hz, 1H), 2.16 (q, J = 7.0 Hz, 2H), 1.41 (q, J = 7.2
Hz, 2H), 1.27 (tt, J = 11.9, 5.4 Hz, 4H), 0.86 (t, J = 6.9 Hz, 3H). 13C NMR
(101 MHz, DMSO-d6): δ 167.56, 149.22, 122.37, 31.79, 31.26, 27.68,
22.35, 14.28.[11]
(E)-3-phenylacrylic acid (2a): White solid, 136.2 mg obtained, yield 92%
from 1a; 130.3 mg obtained, yield 88% from 3a; 122.9 mg obtained, yield
83% from 4. Rf: 0.7 (PE/EA=3:1). H NMR (400 MHz, DMSO-d6) δ 12.44
(s, 1H), 7.73 – 7.65 (m, 2H), 7.61 (d, J = 16.0 Hz, 1H), 7.41 (p, J = 3.5 Hz,
3H), 6.55 (d, J = 16.0 Hz, 1H). 13C NMR (101 MHz, DMSO-d6) δ 168.07,
144.41, 134.69, 130.68, 129.36, 128.67, 119.68.[9]
(E)-4-phenylbut-2-enoic acid (2k): White solid, 108.6 mg obtained, yield
67%. Rf: 0.3 (PE/EA=5:1). 1H NMR (400 MHz, DMSO-d6) δ 12.35 (s, 1H),
7.42 (d, J = 7.2 Hz, 2H), 7.33 (t, J = 7.5 Hz, 2H), 7.24 (t, J = 7.3 Hz, 1H),
6.50 (d, J = 16.0 Hz, 1H), 6.31 (dt, J = 16.0, 7.1 Hz, 1H), 3.20 (dd, J = 7.1,
1.4 Hz, 2H). 13C NMR (101 MHz, DMSO-d6) 13C NMR (101 MHz, DMSO-
d6) δ 173.13, 137.18, 132.70, 129.10, 127.87, 126.49, 123.66, 38.30.[12]
1
(E)-p-methylcinnamic acid (2b): White solid, 147.5 mg obtained, yield
91%. Rf: 0.4 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.37 (s, 1H),
7.62 – 7.51 (m, 3H), 7.20 (d, J = 7.9 Hz, 2H), 6.47 (d, J = 16.0 Hz, 1H),
2.30 (s, 3H). 13C NMR (101 MHz, DMSO-d6) δ 168.18, 144.38, 140.56,
131.94, 129.94, 128.61, 118.52, 21.43.[9]
1-[(tert-butoxy)carbonyl]-1,2,3,6-tetrahydropyridine-4-carboxylic
acid (2l): White solid, 143.1 mg obtained, yield 63% from 1l; 131.7 mg
obtained, yield 58% from 3l. Rf: 0.4 (PE/EA=3:1). 1H NMR (400 MHz,
CDCl3) δ 11.68 (s, 1H), 6.98 (s, 1H), 4.08 (s, 2H), 3.50 (t, J = 5.5 Hz, 2H),
2.40 – 2.33 (m, 2H), 1.44 (s, 9H). 13C NMR (101 MHz, CDCl3) δ 170.93,
154.76, 137.50 (d, J = 63.6 Hz), 128.57, 80.28, 43.62 (d, J = 46.5 Hz),
39.90 (d, J = 126.2 Hz), 28.38, 24.09.[13]
(E)-3-([1,1'-biphenyl]-4-yl)acrylic acid (2c): White solid, 125.5 mg
obtained, yield 56%. Rf: 0.4 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6)
δ 12.43 (s, 1H), 7.82 – 7.61 (m, 7H), 7.49 (t, J = 7.5 Hz, 2H), 7.40 (t, J =
7.3 Hz, 1H), 6.59 (d, J = 16.0 Hz, 1H). 13C NMR (101 MHz, DMSO-d6) δ
168.07, 143.91, 142.17, 139.70, 133.83, 129.49, 129.33, 128.40, 127.53,
127.15, 119.62.[9]
2-phenylacrylic acid (2m): Orange solid, 121.4 mg obtained, yield 82%.
Rf: 0.3 (PE/EA=10:1). 1H NMR (400 MHz, DMSO-d6) δ 12.86 (s, 1H), 7.46
– 7.28 (m, 5H), 6.24 (s, 1H), 5.96 (s, 1H). 13C NMR (101 MHz, DMSO-d6)
δ 168.22, 141.97, 137.18, 128.57, 128.47, 128.42, 126.53.[14]
(E)-3-(4-methoxyphenyl)acrylic acid (2d): White solid, 114.0 mg
obtained, yield 64%. Rf: 0.5 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6)
δ 12.24 (s, 1H), 7.65 (d, J = 8.7 Hz, 2H), 7.55 (d, J = 16.0 Hz, 1H), 6.97 (d,
J = 8.7 Hz, 2H), 6.38 (d, J = 16.0 Hz, 1H), 3.80 (s, 3H). 13C NMR (101 MHz,
DMSO-d6) δ 168.31, 161.38, 144.22, 130.42, 127.27, 116.94, 114.80,
55.77.[9]
(E)-4-ethoxy-4-oxobut-2-enoic acid (2n): White solid, 109.5 mg obtained,
1
yield 76%. Rf: 0.4 (PE/EA=10:1). H NMR (400 MHz, DMSO-d6) δ 13.24
(s, 1H), 6.70 (s, 2H), 4.20 (q, J = 7.1 Hz, 2H), 1.25 (t, J = 7.1 Hz, 3H). 13
C
NMR (101 MHz, DMSO-d6) δ 166.18, 165.01, 135.01, 133.10, 61.44,
14.38.[15]
(E)-4-fluorocinnamic acid (2e): White solid, 136.2 mg obtained, yield
82%. Rf: 0.6 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.42 (s, 1H),
7.80 – 7.70 (m, 2H), 7.60 (d, J = 16.0 Hz, 1H), 7.23 (t, J = 8.8 Hz, 2H), 6.50
4-phenylcyclohex-1-ene-1-carboxylic acid (2o): White solid, 175.8 mg
obtained, yield 87%. Rf: 0.3 (PE/EA=5:1). 1H NMR (400 MHz, CDCl3) δ
12.27 (s, 1H), 7.35-7.39 (m, 2H), 7.26-7.28 (m, 4H), 2.92 – 2.80 (m, 1H),
2.56-2.64 (m, 2H), 2.34-2.44 (m, 2H), 2.08-2.13 (m, 1H), 1.73-1.87 (m, 1H).
4
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10.1002/ejoc.202000288
European Journal of Organic Chemistry
FULL PAPER
13C NMR (101 MHz, CDCl3) δ 173.08, 145.88, 141.97, 129.73, 128.59,
126.85, 126.42, 39.06, 33.97, 29.33, 24.48.[16]
Keywords: • Copper catalyst • Carbon dioxide • Carboxylation •
Alkenyl boron compounds
4,4-difluorocyclohex-1-ene-1-carboxylic
acid
(2p):
Unknown
compound. White solid, 136.1 mg obtained, yield 84%. Rf: 0.5 (PE/EA=5:1).
1H NMR (400 MHz, DMSO-d6): δ 12.50 (s, 1H), 6.74 – 6.67 (m, 1H), 2.70-
2.80 (m, 2H), 2.39-2.44 (m, 2H), 1.97-2.11 (m, 2H). 13C NMR (101 MHz,
DMSO-d6) δ 167.58, 133.87, 129.90, 123.66 (t, J = 239.37 Hz), 34.75
(t, J = 27.27 Hz), 29.70 (t, J = 24.24 Hz), 22.99 (t, J = 5.05 Hz). 19F NMR
(471 MHz, DMSO-d6) δ -94.98 (pd, J = 14.6, 3.1 Hz). HRMS: calculated
for C7H7F2O2[M-H]ｰ 161.041959, found 161.04159.
References
[1]
a) J. Hong, M. Li, J. Zhang, B. Sun, F. Mo,
ChemSusChem 2019, 12, 6-39; b) A. Tortajada, F. Juliá-
Hernández, M. Börjesson, T. Moragas, R. Martin, Angew.
Chem. Int. Ed. 2018, 57, 15948-15982; c) X. Wang, H.
Wang, Y. Sun, Chem 2017, 3, 211-228; d) Q. Liu, L. Wu,
R. Jackstell, M. Beller, Nat. Commun. 2015, 6, 5933; e) Y.
Tsuji, T. Fujihara, Chem. Commun. 2012, 48, 9956-9964;
f) K. Huang, C.-L. Sun, Z.-J. Shi, Chem. Soc. Rev. 2011,
40, 2435-2452; g) A. Correa, R. Martín, Angew. Chem. Int.
Ed. 2009, 48, 6201-6204.
3,3,5,5-Tetramethyl-cyclohexen-carbonsaeure
(2q):
Unknown
compound. White solid, 142.1 mg obtained, yield 78%. Rf: 0.3
(PE/EA=10:1). 1H NMR (400 MHz, DMSO-d6) δ 12.17 (s, 1H), 6.61 (s, 1H),
1.92 (d, J = 1.7 Hz, 2H), 1.31 (s, 2H), 1.03 (s, 6H), 0.92 (s, 6H). 13C NMR
(101 MHz, DMSO-d6) δ 169.06, 146.90, 127.02, 49.11, 37.67, 33.37, 30.81,
30.50, 29.94. HRMS: calculated for C11H17O2[M-H]ｰ 181.123403, found
181.123380.
[2]
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K. Ukai, M. Aoki, J. Takaya, N. Iwasawa, J. Am. Chem.
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a) S.-S. Yan, D.-S. Wu, J.-H. Ye, L. Gong, X. Zeng, C.-K.
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3,6-dihydro-2H-pyran-4-carboxylic acid (2r): Unknown compound.
White solid, 107.6 mg obtained, yield 84%. Rf: 0.4 (PE/EA=3:1). 1H NMR
(400 MHz, DMSO-d6) δ 12.40 (s, 1H), 6.85 (p, J = 2.3 Hz, 1H), 4.18 (q, J
= 2.9 Hz, 2H), 3.68 (t, J = 5.5 Hz, 2H), 2.21 (tq, J = 5.2, 2.4 Hz, 2H). 13
C
NMR (101 MHz, DMSO-d6) δ 167.51, 137.82, 128.27, 64.92, 63.64, 24.67.
HRMS: calculated for C6H8NaO3[M+Na]+ 151.036565, found 151.03658.
1,4-dioxaspiro[4.5]dec-7-ene-8-carboxylic acid (2s): White solid, 134.4
mg obtained, yield 73%. Rf: 0.3 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-
d6) δ 12.23 (s, 1H), 6.72-6,70 (m, 1H), 3.89 (s, 4H), 2.36-2.30 (m, 4H), 1.68
(t, J = 6.4 Hz, 2H). 13C NMR (101 MHz, DMSO-d6) δ 168.15, 136.72,
130.15, 106.97, 64.26, 36.04, 30.70, 23.83.[17]
[4]
a) Z. Zhi-Hua, G. Chun-Xiang, X. Jia-Ning, L. Kai-Xuan, H.
Liang-Nian, Curr. Org. Synth. 2017, 14, 1185-1192; b) X.
Zhang, W.-Z. Zhang, L.-L. Shi, C.-X. Guo, L.-L. Zhang, X.-
B. Lu, Chem. Commun. 2012, 48, 6292-6294.
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Commun. 2014, 50, 8010-8013.
1-benzyloxycarbonyl-1,2,3,6-tetrahydropyridine-4-carboxylic
acid
(2t): Unknown compound. White solid, 216.7 mg obtained, yield 83%. Rf:
0.2 (PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.50 (s, 1H), 7.38-7.31
(m, 5H), 6.86 – 6.79 (m, 1H), 5.11 (s, 2H), 4.12 – 4.03 (m, 2H), 3.50 (d, J
= 8.1 Hz, 2H), 2.29-2.25 (m, 2H). 13C NMR (101 MHz, DMSO-d6) δ 167.57,
154.95, 137.30, 135.50, 135.26, 129.22, 128.89, 128.34, 128.10, 66.76,
43.66, 24.32. HRMS: calculated for C14H16NO4[M+H]+ 262.107384, found
262.107522.
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L. Dang, Z. Lin, T. B. Marder, Organometallics. 2010, 29,
917-927.
a) K. Kuge, Y. Luo, Y. Fujita, Y. Mori, G. Onodera, M.
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Chem. Int. Ed. 2011, 50, 8114-8117.
4-((tert-butoxycarbonyl)amino)cyclohex-1-ene-1-carboxylic acid (2u):
Unknown compound. White solid, 127.8 mg obtained, yield 53%. Rf: 0.3
(PE/EA=3:1). 1H NMR (400 MHz, DMSO-d6) δ 12.18 (s, 1H), 6.87 (d, J =
7.6 Hz, 1H), 6.75-6.73 (m, 1H), 2.41-2.30 (m, 2H), 2.21-1.99 (m, 2H), 1.81-
1.71 (m, 1H), 1.45-1.39 (m, 2H), 1.38 (s, 9H). 13C NMR (101 MHz, DMSO-
d6) δ 168.28, 155.45, 137.43, 130.35, 78.01, 45.48, 31.98, 28.72, 28.55,
23.76. HRMS: calculated for C12H18NO4[M-H]- 240.124132, found
240.123703.
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a) C. Cox, D. Ferraris, N. N. Murthy, T. Lectka, J. Am.
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K. Spektor, M. Y. Skripkin, N. A. Tsyrulnikov, Russ. J.
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3363.
(E)-4-ethyl cinnamic acid (2v): White solid, 149.7 mg obtained, yield 85%.
Rf: 0.3 (PE/EA=10:1). 1H NMR (400 MHz, DMSO-d6) δ 12.38 (s, 1H), 7.61
(s, 1H), 7.57 (d, J = 16.0 Hz, 2H), 7.26 (d, J = 7.9 Hz, 2H), 6.48 (d, J = 15.9
Hz, 1H), 2.62 (q, J = 7.6 Hz, 2H), 1.18 (t, J = 7.6 Hz, 3H). 13C NMR (101
MHz, DMSO-d6) δ 168.19, 146.84, 144.43, 132.22, 128.81, 128.76, 118.61,
28.53, 15.85.[18]
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C.-x. Song, P. Chen, Y. Tang, RSC Advances 2017, 7,
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Acknowledgements
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The project is supported by the Natural Science Foundation of
China (Grant 21772003, 21933001). We also thank Peking
University for a start-up fund. This work was partially funded by
the BHP-PKU CCUS project supported by BHP Billiton.
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10.1002/ejoc.202000288
European Journal of Organic Chemistry
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10.1002/ejoc.202000288
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
Three kinds of alkenyl boron compounds were effetively transformed into the corresponding α, β-unsaturated carboxylic acids in
moderate to high yield through cuprous halide-catalysted carboxylation with CO2. The advantages of this method include low cost,
mild conditions, simple operation, broad scope and external ligand free.
7
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