Diaryl sulfones synthesis with aryltrifluoroborates and aryl sulfinic salts under mild conditions

Article abstract of DOI:10.3184/174751914X13946468223913

CuI-catalysed cross-coupling reactions of various aryltrifluoroborates with aryl sulfinic salts have been achieved in good yields. A new efficient method is described for the conversion of potassium aryltrifluoroborates into diaryl sulfones. The reported reactions are tolerant to common functional groups regardless of whether they are electron-rich or electron-deficient, making this transformation an attractive alternative to traditional approaches.

Full text of DOI:10.3184/174751914X13946468223913

JOURNAL OF CHEMICAL RESEARCH 2014
VOL. 38 MAY, 269–271
RESEARCH PAPER 269
Diaryl sulfones synthesis with aryltrifluoroborates and aryl sulfinic salts
under mild conditions
a
c
b
Wei Zhang , Ke Li and Baoli Zhao *
aDepartment of Chemistry and Chemical Engineering; Xinxiang University; Xinxiang 453003, P.R. China
bInstitute of Applied Chemistry and Department of Chemistry, Shaoxing University, Shaoxing, Zhejiang Province 312000, P.R. China
cJiaozuo City Environmental Protection Bureau, Jiaozuo, Henan Province, 453003, P.R. China
CuI-catalysed cross-coupling reactions of various aryltrifluoroborates with aryl sulfinic salts have been achieved in good yields.
A new efficient method is described for the conversion of potassium aryltrifluoroborates into diaryl sulfones. The reported
reactions are tolerant to common functional groups regardless of whether they are electron-rich or electron-deficient, making
this transformation an attractive alternative to traditional approaches.
Keywords: aryltrifluoroborates, aryl sulfinic salts, cross-coupling, diaryl sulfone synthesis
The transition-metal-catalysed cross-coupling between aryl
sulfinic salts and arylboronic acids is a versatile and widely
utilised transformation in modern synthetic chemistry.
copper acetate catalysed coupling reactions of arylboronic
acids with sulfinic salts in ionic liquids (ILs) to afford aryl
sulfones in good yields under ambient conditions. In 2011, Fu
1–5
5
It is often the method of choice for the preparation of both
symmetrical and unsymmetrical diaryl sulfones, which
constitute the core skeleton of a number of pharmaceutical and
et al. developed a simple and general Cu O-catalysed method
for transformations of arylboronic acids and sulfinate salts in
water at room temperature.
2
6
–9
pesticidal intermediates in organic synthesis.
Another research area in Suzuki–Miyaura-type reactions
which remains underdeveloped is in the search for alternatives
to organoboron cross-coupling partners. Among the most
promising alternatives to arylboronic reagents are potassium
aryltrifluoroborates, which are easily prepared by treatment
of commercially available arylboronic acids or esters with
Over the last 10 years, copper catalysed cross-coupling
strategy for diaryl sulfone synthesis has emerged, using the
coupling of organoboronic acids with various aryl sulfinic
1
salts. (Scheme 1) In 2004, Beaulieu et al. reported a new
efficient and mild preparation of sulfones from boronic acids
and sulfinic salts mediated by 1.1 equiv. copper acetate with
10–14
aqueous KHF2.
Compared to most common organoboron
2
potassium carbonate. In 2007, Tse and co-workers and Huang
compounds, aryltrifluoroborates are completely air- and
moisture-stable, and can be prepared simply and in large
quantities. That they are monomeric species makes their
stoichiometric determination highly reliable. However, the
cross-coupling of potassium aryltrifluoroborates with aryl
sulfinic salts is still underdeveloped. In the report of Huang
3
and Batey respectively described a copper-catalysed method for
the sulfonylation of arylboronic acids with sulfinate salts. The
levels used for Cu(OAc) have been reduced successfully with
2
the assistance of nitrogen-containing ligands in the presence of
4
molecular sieves (4 Å). The next year, Kantam et al. reported
Cu(OAc) 1.1 equiv
2
B(OH)2
SO Na
O
2
K CO 2.0 equiv
2
3
S
Beaulieu's group
Tse's group
4A MS
O
DMSO, rt
Cu(OAc) 0.2eq
SO Na 1-benzylimidazole
2
O
S
B(OH)2
B(OH)2
2
4
A MS
O
o
DMSO, 60 C
Cu(OAc) 0.1eq
2
O
SO Na 1,10-phen 0.2eq
2
S
Batey's group
CH Cl /DMSO (15:1),
2
2
O
O ,4Å MS,40°C
2
B(OH)2
B(OH)2
SO Na
O
2
Cu(OAc) H O 0.1eq
2 2
.
S
Kantam's group
Fu's group
[bmim][OTf], r.t.
O
O
S
SO Na
Cu O 0.1 eq
2
2
.
NH H O, r.t.
3
2
O
Scheme 1 Copper-catalysed cross-coupling between aryl sulfinic salts and arylboronic acids.
Correspondent. E-mail: babygarfield@126.com
*
JCR1402430_FINAL.indd 269
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270 JOURNAL OF CHEMICAL RESEARCH 2014
3
and Batey, the use of potassium trifluorophenyl borate as the
reaction partner led to a disappointing yield (28%) of diphenyl
sulfone. There is still an urgency to develop a new efficient
method for the conversion of potassium trifluorophenyl borates
into diaryl sulfone. We report here a practical synthetic method
to prepare diaryl sulfones using potassium aryltrifluoroborates
in efficient couplings with aryl sulfinic salts catalysed by Cu
salts.
and potassium acetate were the best with 86% and 83% yields,
respectively (entries 6, 12), so we choose sodium acetate as the
optimal base.
Subsequently, to improve this process further, we investigated
the effect of the catalyst and the solvent on the yield. (Table 2).
The cross-coupling reactions of potassium phenyl trifluoborate
with sodium phenylsulfinate were investigated carefully in
order to determine the optimum reaction conditions. The study
of the reaction with several catalysts in DCE showed that the use
of copper salts is necessary to achieve acceptable yields (entries
1–8). Specifically, Cu(I) salts lead to higher yields compared
to Cu(II) salts (entries 1–4 and 5–7). The cross-coupling
reaction proceeds in a higher yield in the presence of CuI
compared to CuOTf, CuCl and CuBr (entries 1–4). Reactions
conducted in various organic solvents occurred with high yield
within 3 h under mild conditions, despite the low solubility of
sodium benzenesulfinate in organic solvents (entries 9–16).
Specifically, chlorinated solvents lead to a higher yields than
other solvents (entries 14–16).
A brief survey indicated that reaction efficiencies are highest
when NaOAc is used as base, DCE is used as solvent and CuI is
used as catalyst. Table 3 summarises the scope of the reactions
conducted under the optimised conditions. The reactions of
the more electron-deficient of the aromatic trifluoroborates
occurred in higher yield than those of the electron-rich
aryltrifluoroborates (entries 1–6). More strikingly, the reaction
of aryltrifluoroborates with substitutions of halogen occurred
with high selectivity (entries 7–10). No by-product was detected
Results and discussion
We optimised the reaction conditions with the potassium
phenyl fluoborate and sodium phenylsulfinate as template
substrates in the presence of 10 mol% Cu(OAc)2 in DCE
1,2-dichloroethane). However, only a 33% yield of diphenyl
sulfone was formed. BF along with BF OH and HF were
formed during the transformation. So we considered that the
addition of base to neutralise the acid and promote the reaction.
When NaF was added to the solution, diphenyl sulfone was
formed 55% yield. We speculate that base may play the role of
accelerator to this copper catalysed process.
(
3
2
CAUTION: These experiments should be carried out taking
due precautions because of the formation of toxic hydrogen
fluoride (HF).
We screened many bases to promote the reaction and the
results are summarised in Table 1. The bases with sodium and
potassium cations were selected as candidates, and the influence
on the reaction of different anions has been studied. The activity
of sodium (entries 1–6) and potassium (entries 7–12) salts
with the same anion is relatively similar and with no obvious
pattern. The comparison between different anions has also been
studied. Carbonate and hydroxide ions promote the reaction
slightly (entries 1–2, 7–8), and tert-butoxy ion, phosphate ion
and bicarbonate ion obviously facilitate the transformation
with yields of 71–79% (entries 3–5, 9–11), Sodium acetate
Table 3 The scope of the reactionsa
O
CuI
BF K +
SO Na
S
3
2
R1
R2
NaOAc
DCE, RT
R1
O
R2
Entry
R1
R2
Yield/%b
1
2
3
4
5
6
7
8
9
4-OCH3
4-CH3
4-t-Bu
H
H
H
H
H
H
H
H
H
H
H
H
82
87
83
90
93
91
89
85
86
83
87
91
88
93
83
87
81
84
89
87
91
90
87
93
Table 1 Base effects on the reactiona
Yield/%b
Yield/%b
Entry
Base
None
Entry
Base
4-COCH3
1
2
3
4
5
6
33
56
79
77
71
86
7
8
9
10
11
12
NaHCO3
K CO
43
52
78
73
76
83
4-NO2
Na CO3
2
2
3
4-CF3
NaOH
KOH
4-F
4-Cl
4-Br
3-Cl
2-F
2-Naphthyl
H
H
H
H
H
H
H
H
H
H
H
H
t-BuONa
Na PO
t-BuOK
K3PO4
KOAc
3
4
NaOAc
aReaction conditions: PhBF3K (1.0 mmol), PhSO Na (1.0 mmol), CuI
10
2
1
1
(
0.1 mmol), base (1.2 mmol), DCE (2 mL), 25 °C, 3 h. See the safety caution.
b
12
c
Isolated yield.
1
3
4-OCH3
4-CH3
1
4
Table 2 Catalyst and solvent selection on the reactiona
1
5
4-t-Bu
Entry
Catalyst
Yield/%b
Entry
Solvent
Yield/%c
16
4-COCH3
4-NO2
4-CF3
4-F
4-Cl
4-Br
3-Cl
2-F
2-Naphthyl
1
2
3
4
5
6
7
8
CuOTf
CuCl
CuBr
77
82
81
86
55
59
47
0
9
10
11
12
13
14
15
16
DMSO
DMF
51
46
50
39
45
77
80
71
17
18
19
20
21
22
23
24
CH CN
3
CuI
toluene
THF
CCl4
Cu(OAc)2
CuCl2
Cu(OTf)2
None
CH Cl
2
2
d
CHCl3
a
aReaction conditions: ArBF3K (1.0 mmol), ArSO Na (1.0 mmol), CuI
Reaction conditions: PhBF K (1.0 mmol), PhSO Na (1.0 mmol), catalyst
3
2
2
(
0.1 mmol), NaOAc (1.2 mmol), solvent (2 mL), 25 °C, 3 h. See safety
(0.1 mmol), NaOAc (1.2 mmol), DCE (2 mL), 25 °C, 3 h. See safety caution.
b
caution.
Isolated yield.
2-Naphthyltrifluoroborate was used.
b
c
Isolated yield using DCE as solvent.
c
d
Isolated yield using CuI as catalyst.
Sodium 2-naphthyl sulfinic acid was used.
JCR1402430_FINAL.indd 270
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JOURNAL OF CHEMICAL RESEARCH 2014 271
1
7
in CuI-catalysed dehalogenation with sulfinate salts. More
bulky substrates also reacted efficiently with sulfinate salts and
gave the product in a comparable yield (entry 11). As shown in
entry 12, we were able to extend the methodology to fused ring
trifluoroborates to afford the desired sulfone in 91% yield under
our standard conditions. Then we chose the same substituents
on sodium aryl sulfinate salts to investigate the scope of the
coupling with respect to other sulfinate salts (Table 3, entries
4-Nitrophenyl phenyl sulfone: Yellow solid, m.p. 145–149 °C (lit.
1
143–145 °C); H NMR (400 MHz, CDCl ): δ 8.27–8.38 (m, 2H),
8.07–8.15 (m, 2H), 7.92–8.00 (m, 2H), 7.58–7.66 (m, 1H), 7.51–7.61 (m,
3
2
H). HRMS calcd for C H NO S: 263.0252, found: 263.0250.
12 9 4
4
-Trifluoromethylphenyl phenyl sulfone: Colourless solid, m.p.
9–90 °C (lit. 90–91 °C); H NMR (400 MHz, CDCl ): δ 8.07
d, J=8.0 Hz, 2H), 7.90–8.03 (m, 2H), 7.80 (d, J=8.8 Hz, 2H),
.50–7.65(m, 3H). HRMS calcd for C H F O S: 286.0275, found:
17
1
8
(
7
2
3
13
9
3
2
86.0276.
-Fluorophenyl phenyl sulfone: White solid, m.p. 103–104 °C (lit.
13–24). The transformation worked equally as well with
15
4
aryltrifluoroborates with a diverse range of substituents, to
afford the products in good to excellent yields.
1
1
05–107 °C); H NMR (400 MHz, CDCl ): δ 7.96 (m, 4H), 7.57 (t,
J=7.6 Hz, 1H), 7.50 (t, J=7.6 Hz, 2H), 7.18 (m, 2H). HRMS calcd for
3
C H FO S: 236.0307, found: 236.0305.
Conclusions
12
9
2
1
7
4
-Chlorophenyl phenyl sulfone: White solid, m.p. 90–91 °C (lit.
In conclusion, we have shown that aryltrifluoroborate salts,
which are water and air stable equivalents of arylboronic acids,
can be utilised in copper-catalysed cross-coupling reactions
with aryl sulfinate salts. Diaryl sulfones derivatives were
easily synthesised in high yields with the assistance of base.
Investigation of the mechanism of these reactions is ongoing in
our laboratory.
1
9
(
2–93 °C); H NMR (400 MHz, CDCl ): δ 7.80–8.01 (m, 4H), 7.44–7.64
m, 5H). HRMS calcd for C H ClO S: 252.0012, found: 252.0017.
3
35
12
9
2
17
4
-Bromophenyl phenyl sulfone: Yellow solid, m.p. 100–101 °C (lit.
1
9
8–99 °C); H NMR (400 MHz, CDCl ): δ 7.88–7.99 (m, 2H), 7.76–7.86
3
(
m, 2H), 7.61–7.69 (m, 2H), 7.55–7.61 (m, 1H),7.46–7.52 (m, 2H).
79
HRMS calcd for C H BrO S: 295.9507, found: 295.9508.
12
9
2
15
3
-Chlorophenyl phenyl sulfone: Yellow solid, m.p. 99–100 °C (lit.
1
1
00–101°C); H NMR (400 MHz, CDCl ): δ 7.93 (m, 3H), 7.82 (d,
3
Experimental
J=7.6 Hz, 1H), 7.62 (t, J=7.6 Hz, 1H), 7.52 (m, 3H), 7.45 (t, J=8.4 Hz,
All solvents were purified and dried according to standard methods
prior to use. Proton NMR spectra were recorded in CDCl on a Bruker
1
H). HRMS calcd for C H ClO S: 252.0012, found: 252.0017.
12 9 2
17
3
2-Fluorophenyl phenyl sulfone: White solid, m.p. 93–96 °C (lit.
Avance III 400 M Hz spectrometer. Proton chemical shifts are reported
in parts per million (ppm) relative to tetramethylsilane (TMS) with
the residual solvent peak as the internal reference. Multiplicities are
9
2–94 °C);
1
H NMR (400 MHz, CDCl ): δ 7.40–7.51 (m, 5 H), 7.09–7.20 (m, 4 H);
C NMR (100 MHz, CDCl ) δ 152.9; 141.4, 136.7; 133.1; 130.2, 129.3,
3
13
3
13
reported as: singlet (s), doublet (d), triplet (t) and multiplet (m).
C
127.5,127.1, 125.8, 117.8; HRMS calcd for C H FO S: 236.0307, found:
12 9 2
NMR spectra were recorded at 100 MHz with TMS as an internal
reference. HRMS (EI) data were collected on high resolution mass
spectrometer (MAT 900 XL, Thermo Finnigan, USA). All materials
were purchased from common commercial sources and used without
additional purification.
2
36.0309.
-Napthyl phenyl sulfone: Colourless solid, m.p. 119–120 °C (lit.
17
2
1
119–121 °C); H NMR (400 MHz, CDCl ): δ 8.58 (s, 1H), 7.95–8.06
3
(m, 3H), 7.93 (d, J=8.8 Hz, 1H), 7.82–7.89 (m, 2H),7.48–7.66 (m, 5H).
HRMS calcd for C H O S: 268.0558, found: 268.0556.
16
12
2
Synthesis; typical procedure
A mixture of potassium arylfluoborate (1 mmol), sodium aryl sulfinate
Received 28 January 2014; accepted 25 February 2014
Paper 1402930 doi: 10.3184/174751914X13946468223913
Published online: 6 May 2014
(1 mmol), CuI (0.1 mmol), sodium acetate (1.2 mmol) and DCE (2 mL)
was stirred at 25 °C under air for 3 h. After filtration, the organic
phases were evaporated under reduced pressure, and the residue was
subjected to flash column chromatography [silica gel, ethyl acetate/
petroleum ether (60–90 °C)=1/8] to obtain the desired product.
References
15
Diphenyl sulfone: White solid, m.p. 126–127 °C (lit. 125–126 °C);
1
C. Beaulieu, D. Guay, Z. Wang and D.A. Evans. Tetrahedron Lett., 2004,
45, 3233.
1
H NMR (400 MHz, CDCl ): δ 7.94 (d, J=7.6 Hz, 4H), 7.55 (t,
3
J=7.6 Hz, 2H), 7.50 (t, J=7.6 Hz, 4H). HRMS calcd for C H O S:
2
A. Kar, I.A. Sayyed, W.F. Lo, H.M. Kaiser, M. Beller and M.K. Tse. Org.
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Fazal, J. Med. Chem., 2004, 47, 18.
12
10
2
2
18.0402, found: 218.0405.
16
3
4
4
-Methoxyphenyl phenyl sulfone: Yellow solid, m.p. 90–92 °C (lit.
1
8
6
8–90 °C); H NMR (300 MHz, CDCl ) δ 7.90 (m, 4H), 7.51 (m, 3H),
3
1
3
.96 (m, 2H), 3.84 (s, 3H); C NMR (100 MHz, CDCl ) δ 162.9, 144.6,
3
5
6
7
8
1
38.7, 133.0, 129.7, 129.0, 127.4, 127.1, 56.1; HRMS calcd for C H O S:
13 12 3
2
48.0507, found: 248.0509.
-Methylphenyl phenyl sulfone: White solid, m.p. 125–127 °C (lit.
15
4
1
126–127 °C); H NMR (400 MHz, CDCl ): δ 7.92 (d, J=8.0 Hz, 2H),
3
9
7.81 (d, J=8.0 Hz, 2H), 7.54 (t, J=7.6 Hz, 1H), 7.49 (t, J=7.6 Hz,
2
2
H), 7.30 (d, J=8.0 Hz, 2H), 2.37 (s, 3H). HRMS calcd for C H O S:
13 12 2
10 J. Masllorens, I. González and A. Roglans, Eur. J. Org. Chem., 2007, 158.
11
32.0558, found: 232.0557.
-tert-Butylphenyl phenyl sulfone: White solid, m.p. 129–131 °C
L.S. Varnedoe, B.D. Angel, J.L. McClellan and J.M. Hanna Jr, Lett. Org.
Chem., 2010, 7, 1.
4
17
1
(
lit. 127–128 °C); H NMR (400 MHz, CDCl ): δ7.94–7.98 (m, 2H),
12 N. Taccardi, R. Paolillo, V. Gallo, P. Mastrorilli, C.F. Nobile, M. Räisänen
3
7
.83–7.88 (m, 2H), 7.47–7.57 (m, 5H), 1.35 (s, 9H). HRMS calcd for
and T. Repo, Eur. J. Inorg. Chem., 2007, 4645.
1
14
3
B. Schmidt and F. Hölter, Org. Biomol. Chem., 2011, 9, 4914.
S. Cacchi, E. Caponetti, M.A. Casadei, A.D. Giulio, G. Fabrisi, G. Forte,
A. Goggiamani, S. Moreno, P. Paolicelli, F. Petrucci, A. Prastaro and M.L.
Saladino, Green Chem., 2012, 14, 317.
C H O S: 274.1028, found: 274.1031.
16
18
2
4
-Acetylphenyl phenyl sulfone: Yellow solid, m.p. 132–133 °C
16
1
(
lit. 132–134 °C); H NMR (400 MHz, CDCl ) δ 7.94–8.04 (m, 6H),
3
13
7.50–7.61 (m, 3H), 2.63 (s, 3H); C NMR (100 MHz, CDCl ) δ196.4,
3
15 H. Yang, Y. Li, M. Jiang, J. Wang and H. Fu, Chem. Eur. J., 2011, 17, 5652.
16 W. Zhu and D. Ma, J. Org. Chem., 2005, 70, 2696.
142.9, 140.7, 140.1, 133.7, 130.1, 129.2, 128.8, 127.3, 27.6; mHRMS
calcd for C H O S: 260.0507, found: 260.0510.
17 B.P. Bandgar, S.V. Bettigeri and J. Phopase, Org. Lett., 2004, 6, 2105.
14
12
3
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