Copper(I)-catalyzed carboxylation of aryl- and alkenylboronic esters

Article abstract of DOI:10.1021/ol800829q

(Chemical Equation Presented) The copper(I)-catalyzed carboxylation reaction of aryl- and alkenylboronic esters proceeded smoothly under CO ₂ to give the corresponding carboxylic acid in good yield. This reaction showed wide generality with higher functional group tolerance compared to the corresponding Rh(I)-catalyzed reaction.

Full text of DOI:10.1021/ol800829q

[
Supporting Information]
Copper(I)-catalyzed Carboxylation of Aryl- and Alkenylboronic Esters
Jun Takaya, Satoshi Tadami, Kazutoshi Ukai, and Nobuharu Iwasawa*
Department of Chemistry, Tokyo Institute of Technology, O-okayama, Meguro-ku,
Tokyo 152-8551, Japan
Contents
1
2
) Experimental section and analytical data for new compounds
SI1-SI8
1
13
) Copies of H NMR, C NMR and IR spectra for new compounds
and carboxylation products
SI9-SI98
1
13
General. H and C-NMR spectra were recorded on a JEOL Lambda-400 (400 MHz
1
13
1
13
for H and 100 MHz for C), a JEOL AL-400 (400 MHz for H and 100 MHz for C), a
1
13
JEOL Lambda-300 (300 MHz for H and 75 MHz for C) or a JEOL AL-300 (300 MHz
1
13
1
13
for H and 75 MHz for C) spectrometer using CHCl ( H, δ = 7.26), CDCl ( C, δ =
3
3
1
13
7
7.0), DMSO ( H, δ = 2.49), DMSO ( C, δ = 40.45) as an internal standard. IR spectra
were recorded on an FT/IR-460 plus (JASCO Co., Ltd.) or a Spectrum 100 with
universal ATR sampling accessory (Perkim Elmer instruments). Flash column
chromatography was conducted on silica gel 60N (Kanto Chemical Co., Inc.). THF was
purified by solvent purification system of Glass Contour. Dehydrated
N,N-dimethylformamide, diethyl ether and dichloromethane were purchased from
Kanto Chemicals. Recycling preparative GPC-HPLC was carried out on LC-918
(
Japan Analytical Industry Co., Ltd.) using JAIGEL-2H. Cesium fluoride (Wako Pure
Chemical Industries, Ltd.) was dried by heating at 150 ˚C for 2 days in vacuo.
preparation of bisoxazoline ligand 1:
5
,5-Bis(4,5-dihydrooxazol-2-yl)nonan 1
Bu Bu
O
O
N
N
1
Under
an
argon
atmosphere,
1
N,N’-bis(2-chloroethyl)-2,2-di-n-butylpropan-1,3-diamide (2.92 g, 8.61 mmol) was
SI1

added to 5% NaOH / MeOH (NaOH 1.31 g, MeOH 24 ml) and the mixture was
refluxed for 2 hours. The reaction mixture was cooled to room temperature and the
solvent was removed under reduced pressure. The resulting solids were dissolved in
water (20 ml), followed by extraction 6 times with methylene chloride. After the
4
combined organic layer was dried over MgSO , the solvent was removed under reduced
pressure to give crude product (2.05 g). The crude product was purified by
recrystllization from hexane to give 1 (1.59 g, 5.97 mmol, 62% from 6) as colorless
crystal.
-
1
IR (KBr): 2957, 2925, 2902, 2871, 1652 cm .
1
3
H-NMR (400 MHz, CDCl ): δ = 0.88 (6H, t, J = 7.2 Hz), 1.08-1.22 (4H, m), 1.22-1.39
(
1
4H, m), 1.85-1.98 (4H, m), 3.87 (4H, t, J = 9.2 Hz), 4.23 (4H, t, J = 9.2 Hz).
3
C-NMR (100 MHz, CDCl
3
): δ = 14.0, 22.9, 26.1, 32.7, 45.9, 54.2, 67.5, 168.5.
Anal. Calcd. For C15
0.29.
26 2 2
H N O : C 67.63; H 9.84; N 10.52; Found: C 67.34; H 9.67; N
1
preparation of aryl- or alkenylboronic esters:
2
2
2
3
3
3
4
2
a , 2b , 2c , 2d , 2e , 2l and 4a were prepared according to the literature
procedures. 2f, 2g, 2h, 2j and 4e were prepared from the corresponding bromobenzene
or bromostyrene derivatives according to the literature procedure using
5
2
,2-dimethylpropan-1,3-diol instead of ethylene glycol.
5
,5-Dimethyl-2-[4-(phenylethynyl)phenyl]-1,3,2-dioxaborinane (2f)
O
Ph
B
O
2f
-
1
IR (KBr) 3076, 3033, 2956, 2937, 2900, 2211, 1604, 1478, 1421 cm ;
1
H NMR (CDCl ) (400 MHz): δ = 1.04 (6H, s), 3.78 (4H, s), 7.30-7.39 (3H, m),
3
7
.50-7.58 (4H, m), 7.80 (2H, d, J = 8.4 Hz);
1
3
C NMR (CDCl ) (100 MHz): δ = 22.0, 31.9, 72.3, 89.7, 90.3, 123.2, 125.2, 128.18,
3
1
28.25, 130.6, 131.5, 133.6 (1CC-B missing);
Anal. Calcd for C H BO : C 78.65, H 6.60. Found: C 78.54, H 6.70.
1
9
19
2
5
,5-Dimethyl-2-(4-(oct-1-yn-1-yl)phenyl)-1,3,2-dioxaborinane (2g)
O
B
O
2g
SI2

-
1
IR (KBr) 3072, 3030, 2958, 2932, 2871, 2857, 2223, 1603, 1477, 1421 cm ;
1
H NMR (CDCl ) (400 MHz): δ = 0.91 (3H, t, J = 7.2 Hz), 1.02 (6H, s), 1.26-1.40 (4H,
3
m), 1.41-1.52 (2H, m), 1.61 (2H, tt, J = 7.6, 7.2 Hz), 2.41 (2H, t, J = 7.2 Hz ), 3.76 (4H,
s), 7.38 (2H, d, J = 8.0 Hz), 7.72 (2H, d, J = 8.0 Hz);
1
3
C NMR (CDCl ) (100 MHz): δ = 14.1, 19.6, 21.9, 22.6, 28.7, 28.8, 31.4, 31.9, 72.3,
3
8
0.9, 91.5, 126.2, 130.5, 133.5 (1CC-B missing);
Anal. Calcd for C H BO : C 76.52, H 9.13. Found: C 76.32, H 9.20.
1
9
27
2
5
,5-Dimethyl-2-(4-ethenylphenyl)-1,3,2-dioxaborinane (2h)
O
B
O
2h
-1
IR (KBr) 2960, 2928, 2873, 1605, 1479, 1423 cm ;
1
H NMR (CDCl ) (400 MHz): δ = 1.03 (6H, s), 3.78 (4H, s), 5.28 (1H, d, J = 11.0 Hz),
3
5
7
.81 (1H, d, J = 17.8 Hz), 6.74 (1H, dd, J = 17.8, 11.0 Hz), 7.41 (2H, d, J = 8.0 Hz),
.77 (2H, d, J = 8.0 Hz);
1
3
C NMR (CDCl ) (100 MHz): δ = 21.9, 31.9, 72.3, 114.4, 125.4, 134.1, 137.0, 139.6
3
(
1CC-B missing);
Anal. Calcd for C H BO : C 72.26, H 7.93. Found: C 72.50, H 8.13.
1
3
17
2
5
,5-Dimethyl-2-(4-bromophenyl)-1,3,2-dioxaborinane (2j)
O
Br
B
O
2j
-
1
IR (KBr) 3050, 2958, 2939, 2903, 1584, 1480, 1422 cm ;
1
H NMR (CDCl ) (400 MHz): δ = 1.02 (6H, s), 3.76 (4H, s), 7.48 (2H, d, J = 8.3 Hz),
3
7
.65 (2H, d, J = 8.3 Hz) ;
1
3
C NMR (CDCl ) (100 MHz): δ = 21.9, 31.9, 72.3, 125.6, 130.7, 135.5 (1C missing);
C-B
3
Anal. Calcd for C H BBrO : C 49.12, H 5.25. Found: C 49.35, H 5.53.
11
14
2
5
,5-Dimethyl-2-(1-phenylethen-1-yl)-1,3,2-dioxaborinane (4e)
O
B
Ph
O
4
e
IR (neat) 3056, 3025, 2962, 2933, 2890, 1597, 1476, 1415, 1340, 1251, 1230, 1197,
-
1
1
104, 1001, 943, 912, 781, 731, 699, 644 cm ;
1
H NMR (CDCl ) (400 MHz): δ = 1.05 (6H, s), 3.75 (4H, s), 5.97 (1H, d, J = 3.4 Hz),
3
SI3

6
.07 (1H, d, J = 3.4 Hz), 7.27 (1H, t, J = 7.3 Hz), 7.35 (2H, t, J = 7.3 Hz), 7.45 (2H, d, J
=
7.3 Hz);
1
3
C NMR (CDCl ) (100 MHz): δ = 21.8, 31.6, 72.3, 126.6, 127.5, 127.9, 129.5, 142.4
3
(
1CC-B missing);
Anal. Calcd for C H BO : C 72.26, H 7.93. Found: C 72.05, H 7.63.
1
3
17
2
Arylboronic esters 2k and 4b were prepared by esterification of the corresponding
commercially available arylboronic acids: To a mixture of arylboronic acid (3.0 mmol)
and 2,2-dimethylpropan-1,3-diol (3.3 mmol) in CH Cl (6.0 ml) was added MgSO (4.0
2
2
4
g) and the mixture was stirred at room temperature overnight. After filtration, the
solvent was evaporated and the crude product was purified by silica gel chromatography
(
5~10% ethyl acetate in hexanes) or by recrystallization from hexane and ethyl acetate.
5
,5-Dimethyl-2-(4-iodophenyl)-1,3,2-dioxaborinane (2k)
O
B
I
O
2
k
-1
IR (KBr) 2955, 1579, 1479, 1421 cm ;
1
H NMR (CDCl ) (300 MHz): δ = 1.02(6H, s), 3.75 (4H, s), 7.51 (2H, d, J = 6.6 Hz),
3
7
.70 (2H, d, J = 6.6 Hz);
1
3
C NMR (CDCl ) (75 MHz): δ = 21.9, 31.9, 72.3, 98.1, 135.5, 136.7 (1C missing);
C-B
3
Anal. Calcd for C H BIO : C 41.82, H 4.47. Found: C 41.92, H 4.54.
11
14
2
5
,5-Dimethyl-2-(2-cyclohexylethen-1-yl)-1,3,2-dioxaborinane (4b)
O
B
O
4
b
-1
IR (KBr) 2925, 2851, 1634, 1476, 1413 cm ;
1
H NMR (CDCl ) (300 MHz): δ = 0.97 (6H, s), 1.03-1.35 (5H, m), 1.52-1.78 (5H, m),
3
1
6
.92-2.08 (1H, m), 3.63 (4H, s) 5.29 (1H, dd, J = 18.0, 1.2 Hz), 6.49 (1H, dd, J = 18.0,
.6 Hz);
1
3
C NMR (CDCl ) (75 MHz): δ = 21.9, 26.0, 26.2, 31.8, 32.2, 43.0, 72.1, 157.2 (1C
C-B
3
missing);
Anal. Calcd for C H BO : C 70.29, H 10.44. Found: C 70.30, H 10.15.
1
3
23
2
6
Preparation of 2i :
SI4

A mixture of 4-bromonitrobenzene (202 mg, 1.00 mmol), bis(neopentyl
glycolato)diboron (247 mg, 1.09 mmol), PdCl (dppf) (21.8 mg, 0.03 mmol) and
2
potassium acetate (290 mg, 3.04 mmol) in DMSO (6 ml) was heated at 80 ˚C for 5
hours. The reaction was quenched by adding water and the mixture was filtered through
a short pad of Celite. The filtrate was extracted four times with ether and combined
organic layer was washed with brine, and dried over MgSO . Solvent was removed
4
under reduced pressure to give crude product. This crude product was purified by
silica gel chromatography (10% ethyl acetate in hexanes) to afford 2i (125 mg, 0.53
mmol, 53%).
5
,5-Dimethyl-2-(4-nitrophenyl)-1,3,2-dioxaborinane (2i)
O
O N
B
2
O
2
i
IR (KBr) 2963, 1514, 1478, 1425, 1348, 1333, 1309, 1255, 1125, 851, 729, 700, 633
-
1
cm ;
1
H NMR (CDCl ) (300 MHz): δ = 1.04 (6H, s), 3.80 (4H, s), 7.98 (2H, d, J = 8.8 Hz),
3
8
.17 (2H, d, J = 8.8 Hz);
1
3
C NMR (CDCl ) (100 MHz): δ = 21.8, 31.9, 72.4, 122.2, 134.7, 149.6 (1C missing);
C-B
3
Anal. Calcd for C H BNO : C 56.21, H 6.00, N 5.96. Found: C 56.19, H 6.16, N
11
14
4
5
.86.
Preparation of 2m:
To a stirred solution of benzothiophene (1.75 ml, 15.0 mmol) in THF (75 ml) was
added n-butyllithium (9.6 ml, 1.56 M) at –40 ˚C. After 2 h, triethylborate (2.80 ml, 16.5
mmol) was added dropwise over 5 min at –40 ˚C and the mixture was stirred overnight
at the same temperature. The mixture was treated with 1 M HCl and then extracted with
AcOEt three times. To the combined organic layer was added Na SO and
2
4
2
,2-dimethyl-1,3-propanediol (1.58 g, 15.2 mmol), and the mixture was stirred
overnight. Removal of the solvent under reduced pressure afforded white solids,
which were recrystallized to give 2m (2.42 g, 9.8 mmol) in 66% yield.
5
,5-Dimethyl-2-(benzothiophen-2-yl)-1,3,2-dioxaborinane (2m)
O
B
S
O
2
m
SI5

-
1
IR (KBr) 3055, 3022, 2954, 2906, 2867, 1518, 1493, 1480, 1455 cm ;
1
H NMR (CDCl ) (300 MHz): δ = 1.05 (6H, s), 3.80 (4H, s), 7.32-7.37 (2H, m),
3
7
.81-7.97 (3H, m);
1
3
C NMR (CDCl ) (75 MHz): δ = 21.8, 32.0, 72.5, 122.5, 123.9, 124.2, 124.9, 132.8,
3
1
40.6, 143.4 (1CC-B missing);
Anal. Calcd for C H BO S: C 63.44, H 6.14, S 13.03. Found: C 63.74, H 6.34, S
13
15
2
1
3.01.
7
Preparation of 4d :
A mixture of p-trifluoromethylphenylacetylene (2.57 g, 15.1 mmol) and
catecholborane (2.5 ml, 23.5 mmol) was heated at 70 ˚C for 4 hours. The reaction was
quenched by adding water and the mixture was stirred for 9 hours at room temperature.
The mixture was extracted with AcOEt three times, and the combined organic layer was
washed with water (2 times) and brine, and dried over MgSO . After removal of
4
solvent under reduced pressure, 2,2-dimethylpropan-1,3-diol (1.76g, 16.9 mmol) and
toluene (40 ml) were added and the mixture was heated to reflux with the azeotropic
removal of water. Organic layer was extracted with ether and the combined ether extract
was washed with water three times, dried over MgSO . After removal of solvent under
4
reduced pressure, the residue was purified by silica gel chromatography (10% ethyl
acetate in hexanes) and recrystallization from hexane to give the alkenylboronic ester 4d
(
860 mg, 20 %, 2 steps).
5
,5-Dimethyl-2-[2-(4-trifluoromethylphenyl)ethen-1-yl)]-1,3,2-dioxaborinane (4d)
O
B
F3C
O
4d
IR (KBr) 3055, 3016, 2962, 2905, 1631, 1615, 1577, 1477, 1415, 1378, 1314, 1282,
-
1
1
259, 1172, 1111, 1066, 1014, 990, 819, 679, 588, 498 cm ;
1
H NMR (CDCl ) (400 MHz): δ = 1.01 (6H, s), 3.71 (4H, s), 6.20 (1H, d, J = 18.4 Hz),
3
7
.33 (1H, d, J = 18.4 Hz), 7.53-7.61 (4H, m);
1
3
C NMR (CDCl ) (100 MHz): δ = 21.9, 31.9, 72.2, 124.1(1C, q, J = 270.6 Hz), 125.4
CF
3
(
1C, q, J = 3.3 Hz), 127.0, 130.0 (1C, q, J = 32 Hz), 141.0, 145.3 (1C missing);
CF
CF
C-B
Anal. Calcd for C H BF O : C 59.19, H 5.68. Found: C 59.44, H 5.85.
1
4
16
3
2
Preparation of 4c:
SI6

A mixture of 3,3-dimethyl-1-butyne (1.0 ml, 8.2 mmol) and dibromoborane
dimethylsulfide complex (1 M CH Cl sol., 8.2 ml, 8.2 mmol) in methylene chloride (8
2
2
ml) was stirred overnight at room temperature. After removal of solvent, 1 M aq. NaOH
8.0 ml) was slowly added to give precipitates, which were collected by suction
(
filtration. The filtrate was extracted with methylene chloride and the solvent was
removed under reduced pressure. To the residue was added a small amount of 1M aq.
NaOH to give precipitates, which were collected again by suction filtration. The
combined precipitates (609 mg) were used for the next esterification.
To a solution of the above precipitates and 2,2-dimethylpropan-1,3-diol (850 mg 8.16
mmol) in ether was added Na CO , and the mixture was stirred overnight at room
2
3
temperature. Filtration and evaporation gave crude product (white solid, 1.12 g). A part
of this crude product (ca. 700 mg) was purified by GPC to give 4c (423 mg, 2.2 mmol)
in 27 % yield (2 steps).
5
,5-Dimethyl-2-(2-t-butylethen-1-yl)-1,3,2-dioxaborinane (4c)
O
B
O
4
c
-1
IR (KBr) 2960, 2869, 1634, 1477, 1414 cm ;
1
H NMR (CDCl ) (300 MHz): δ = 0.97 (6H, s), 1.01 (9H, s), 3.64 (4H, s) 5.26 (1H, d, J
3
=
18.3 Hz), 6.55 (1H, d, J = 18.3 Hz);
1
3
C NMR (CDCl ) (75 MHz): δ =21.9, 29.0, 31.8, 34.6, 72.1, 161.8 (1C missing);
C-B
3
Anal. Calcd for C H BO : C 67.37, H 10.79. Found: C 67.08, H 10.59.
11
21
2
General procedure for copper-catalyzed carboxylation of arylboronic esters with
carbon dioxide (in the presence of bis(oxazoline)):
A DMF suspension (2.5 ml) of CuI (1.9 mg, 0.01 mmol), bisoxazoline ligand 1 (2.9
mg, 0.01 mmol), arylboronic ester (0.2 mmol) and CsF (0.60 mmol, 91 mg) was stirred
in a glass tube (φ = 1.7 cm, 18 cm) under an atmospheric pressure of CO and then the
2
system was closed. The mixture was heated at 90 ˚C for 10 hours, and then the reaction
was quenched with 1 M HCl aq. Organic layer was extracted with Et O four times and
2
the combined extract was dried over MgSO . After removal of the solvent under
4
reduced pressure, the residue was purified by silica gel chromatography (hexane :
CH Cl = 7:1 – 0:1, followed by CH Cl : ethyl acetate = 9:1) or by reverse extraction
2
2
2
2
(
Et O/aq. NaHCO then Et O/ aq. HCl) followed by filtration through silica gel to
2 3 2
afford corresponding carboxylic acids.
SI7

General procedure for copper-catalyzed carboxylation of alkenylboronic esters
with carbon dioxide (in the absence of bis(oxazoline)):
A DMF suspension (2.5 ml) of CuI (1.9 mg, 0.01 mmol), alkenylboronic ester (0.2
mmol) and CsF (0.60 mmol, 91 mg) was stirred in a glass tube (φ = 1.7 cm, 18 cm)
under an atmospheric pressure of CO and then the system was closed. The mixture was
2
heated at 90 ˚C for 10 hours, and then the reaction was quenched with 1 M HCl aq.
Organic layer was extracted with Et O four times and the combined extract was dried
2
over MgSO . After removal of the solvent under reduced pressure, the residue was
4
purified by silica gel chromatography (hexane : CH Cl = 7:1 – 0:1, followed by
2
2
CH Cl : ethyl acetate= 9:1) or by reverse extraction ( Et O/aq. NaHCO then Et O/ aq.
2
2
2
3
2
HCl) followed by filtration through silica gel to afford corresponding carboxylic acids.
8
9
10
11
12
Spectroscopic data of carboxylic acids 3f , 3g , 5b , 5c and 5e were reported in the
literature. Other carboxylic acids were commercially available.
References
(
1) N,N’-Bis(2-chloroethyl)-2,2-di-n-butylpropan-1,3-diamide was prepared according
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(
8
(
(
(
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(
(
(
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(
(
(
(
9) Gavrin, A. J.; Douglas, E. P. Macromolecules 2001, 34, 5876.
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