Hypervalent iodine in synthesis. 83. Palladium-catalyzed carbonylative coupling of diaryliodonium salts mediated by indium

Article abstract of DOI:10.1081/SCC-120014772

In the presence of palladium catalyst and indium diaryl-iodonium salt; react with carbon monoxide under mild reaction conditions to give diaryl ketone; in moderate yields.

Full text of DOI:10.1081/SCC-120014772

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HYPERVALENT IODINE IN SYNTHESIS. 83. PALLADIUM-
CATALYZED CARBONYLATIVE COUPLING OF
DIARYLIODONIUM SALTS MEDIATED BY INDIUM
a
b
Tao Zhou & Zhen-Chu Chen
a
Faculty of Life Science and Biotechnology , Ningbo University , Zhejiang, 315211, P.R.
China
b
Department of Chemistry , Zhejiang University (Xixi Campus) , Hangzhou, 310028, P.R.
China
Published online: 22 May 2009.
To cite this article: Tao Zhou & Zhen-Chu Chen (2002) HYPERVALENT IODINE IN SYNTHESIS. 83. PALLADIUM-CATALYZED
CARBONYLATIVE COUPLING OF DIARYLIODONIUM SALTS MEDIATED BY INDIUM, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 32:22, 3431-3435, DOI: 10.1081/SCC-120014772
To link to this article: http://dx.doi.org/10.1081/SCC-120014772
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 22, pp. 3431–3435, 2002
HYPERVALENT IODINE IN SYNTHESIS.
8
3. PALLADIUM-CATALYZED
CARBONYLATIVE COUPLING OF
DIARYLIODONIUM SALTS
MEDIATED BY INDIUM
1,2
Tao Zhou and Zhen-Chu Chen1,*
1
Department of Chemistry, Zhejiang University
Xixi Campus), Hangzhou, 310028, P.R. China
(
2
Faculty of Life Science and Biotechnology,
Ningbo University, Zhejiang, 315211, P.R. China
ABSTRACT
In the presence of palladium catalyst and indium diaryl-
iodonium salt; react with carbon monoxide under mild
reaction conditions to give diaryl ketone; in moderate yields.
In the previous paper we have reported catalytic reductive coupling of
diaryliodonium salts promoted by palladium–indium system to form biaryls
[1]
in good yields. We have found that addition of carbon monoxide to the
reaction mixture results in the formation of symmetrical ketones. Here we
wish to report preliminary results of an investigation on palladium–indium
promoted carbonylative coupling of diaryliodonium salts to diaryl ketones.
*
Corresponding author.
3
431
DOI: 10.1081/SCC-120014772
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3
432ZHOU AND CHEN
Scheme 1.
In fact, in the presence of palladium catalyst and indium, simple
stirring a solution of diaryliodonium salts in DMF under one atmosphere
pressure of carbon monoxide at room temperature gave, after work up and
isolation, the diaryl ketone (Sch. 1).
In order to determine the optimum conditions for this reaction, we
examined the effects of several factors on the carbonylative coupling of
diphenyliodonium tetrafluoroborate. We found that solvent and palladium
catalyst have obvious effects on the reaction. Among the selected solvents
including DMF, acetone, DME, THF and dioxane, DMF is the best choice.
Among the three tested palladium catalysts, Pd(OAc) is the most effective.
2
Examination of the reaction of diphenyliodonium tetrafluoroborate showed
that except the major product benzophenone, biphenyl was obtained in 13%
yield, but benzil was not obtained (Entry 1). This reaction also exhibits a
dependence of the anion associated with the iodonium salts (Table 1,
ꢀ
ꢀ
Entries 9, 10, 14). In particular, BF results in higher yields than Cl ,
4
ꢀ
ꢀ
Br , I . When we use diaryliodonium halide instead of diaryliodonium
tetrafluoroborate, we found that except diaryl ketone, dicarbonylation
product was also obtained in 5, 10and 32% yield respectively (Entries 9,
1
0, 14). We also found that the reaction could not occur in the absence of
indium (Entry 8).
A variety of diaryliodonium salts with various substituents including
methyl, chloro, methoxy, nitro and bromo were tested. It was found that all
of them can undergo the carbonylative coupling rapidly in the presence of
carbon monoxide, Pd(OAc) and indium at room temperature. The results
2
are summarized in Table 1. All the products gave satisfactory m.p., IR and
1
H NMR data consistent with literature data.
The mechanism of this reaction is not clear at the present stage.
However, we consider that Ar-Pd-X and ArCOPdX formed as intermediates
act an important role in this reaction. One possible pathway is a reaction of an
arylpalladium compound with an acylpalladium compound to via a direct
electron transfer from indium to form acylarylpalladium compound which
occurs a reductive elimination to afford diaryl ketone. It is shown in Sch. 2.
As shown in Sch. 1, iodoarene was the another product in the reaction.
However, it was easily converted to diaryliodonium salts in sufficient yield
[
1]
as described in our previous paper.

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HYPERVALENT IODINE IN SYNTHESIS. 83
3433
Table 1. Carbonylative Coupling of Diaryliodonium Salts with Palladium–Indium
a
System
b
Yield
(%)
þ
4ꢀ
Entry
Ar
2
I BF
Solvent
DMF
Acetone Pd(OAc)
Catalyst
Product
þ
ꢀ
1
2
3
4
5
6
7
Ph
1a
1a
1a
1a
1a
1a
1a
Ph
2
I BF
4
1a
Pd(OAc)
2
2
2
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2b
2c
2d
2d
2e
2f
71
50
38
33
16
60
55
0
60
55
67
64
58
25
57
44
THF
DME
Pd(OAc)
Pd(OAc)2
Dioxane Pd(OAc)
2
DMF
DMF
DMF
DMF
DMF
DMF
DMF
PdCl
Pd(PPh3)4
Pd(PPh
Pd(OAc)
Pd(OAc)2
2
(PPh
3
)
2
c
8
3 4
)
þ
þ
ꢀ
ꢀ
0
00
9
2
I Cl 1a
I Br 1a
2
1
1
1
1
1
1
1
0Ph
1
2
3
4
2
þ
ꢀ
( p-Tol)
( p-ClC
2
I BF
4
1b
Pd(OAc)
Pd(OAc)
2
2
þ
ꢀ
1c
H
6 4
)
2
I BF
4
þ
ꢀ
( p-CH OC H ) I BF 1d DMF
4
Pd(OAc)2
Pd(OAc)2
Pd(OAc)
Pd(OAc)
3
6
4 2
þ
ꢀ
0
( p-CH OC H ) I
3
I
1d
DMF
DMF
DMF
6
4 2
þ
ꢀ
5
6
( p-BrC
(m-NO
H
6 4
)
2
I BF
þ
4
1e
ꢀ
2
2
2
C
6
H
4
)
2
I BF
4
1f
a
The reaction was carried out under 1 atm. CO atmosphere at room temperature
in 5 mL solvent for 1 h in the presence of 1 mmol diaryliodonium salt, 5 mol%
b
c
palladium catalyst and 0.5 mg-atom indium; Yield of isolated product; Indium
was absent, the amount of palladium catalyst was stoichometric.
Scheme 2.
In conclusion, the carbonylative coupling reaction of diaryliodonoum
salts can proceed rapidly in the presence of Pd(OAc) and indium at room
2
temperature under one atmosphere pressure of carbon monoxide to give
symmetrical diaryl ketones in moderate yields. With the advantages of

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3
434
ZHOU AND CHEN
simple operation, mild reaction conditions and reasonable yield, it offers a
convenient method for the preparation of diaryl ketones. Furthermore, the
range of useful application of indium-mediated transformations in organic
synthesis has been extended.
EXPERIMENTAL
1
Melting points were uncorrected. H NMR data were recorded on
Advance 400 spectrometer using CDCl as the solvent with TMS as an
3
internal standard. IR spectra were determined on Vector 22 infrared
spectrometer with KBr pallet.
General Procedure for the Preparation of Diaryl Ketones
A mixture of diaryliodonium salt (1) (1 mmol), indium (0.5 mg-atom,
cut into small slices), Pd(OAc) (5 mol%) and DMF (5 mL) was stirred
2
under carbon monoxide at room temperature for 1 h. The reaction mixture
was diluted with saturated NH Cl aqueous (20mL), and extracted with
4
diethyl ether (3 ꢁ 15 mL). The combined organic layer was washed with
brine, dried over anhydrous sodium sulfate. After removal of the solvent
under vacuum, the residue was chromatographed on silica gel plate using
n-hexane/ethyl acetate (9 : 1) for 2a–d and n-hexane/ethyl acetate (6 : 1) for
2e, 2f as a developer to give pure product (2).
Physical and Spectroscopic Data
ꢂ
[2]
ꢂ
1
Benzophenone 2a: M.p. 48–50 C (lit. 49–51 C). H NMR ꢀ 7.49
H
ꢀ1
(
m, 4H), 7.60(m, 2H), 7.80(m, 4H). IR
ꢁmax/cm 3060, 1660, 1599,
1
578, 1448, 1318, 1278, 1176, 942, 920, 764, 701, 639.
0
ꢂ
[3]
ꢂ
4
,4 -Dimethylbenzophenone 2b: M.p. 92–94 C (lit.
95–95.5 C).
ꢀ1
1
H NMR ꢀH 2.44 (s, 6H), 7.27 (m, 4H), 7.70(m, 4H). IR ꢁmax/cm 1644,
1
604, 1509, 1458, 1318, 1257, 1165, 1022, 931, 851, 838, 770.
0
ꢂ
[4]
,4 -Dichlorobenzophenone 2c: M.p. 146–147 C (lit. 147–148 C).
ꢂ
4
1
ꢀ1
H NMR ꢀH 7.47 (m, 4H), 7.72 (m, 4H). IR ꢁmax/cm 1654, 1588, 1484,
1
399, 1308, 1286, 1089, 1014, 929, 852, 832, 754, 669.
0
ꢂ
[5]
ꢂ
176 C).
4
,4 -Dibromobenzophenone 2d: M.p. 174–176 C (lit.
ꢀ1
1
H NMR ꢀH 7.65 (s, ArH). IR ꢁmax/cm 1643, 1607, 1312, 1278, 1177,
27, 751.
9

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HYPERVALENT IODINE IN SYNTHESIS. 83
3435
0
ꢂ
[6]
,4 -Dimethoxybenzophenone 2e: M.p. 142–144 C (lit. 144–145 C).
ꢂ
4
1
ꢀ1
H NMR ꢀH 3.89 (s, 6H), 6.96 (d, 4H), 7.79 (d, 4H). IR ꢁmax/cm 1645,
1
584, 1396, 1303, 1289, 1073, 1012, 928, 955, 826, 751, 663.
0
ꢂ
[7]
ꢂ
152–153 C).
3
,3 -Dinitrobenzophenone 2f: M.p. 150–152 C (lit.
1
H NMR ꢀH 7.73 (m, 2H), 8.45 (m, 1H), 8.47 (m, 1H), 8.49 (m, 1H), 8.51
ꢀ
1
(
1
m, 1H), 8.97 (m, 2H). IR ꢁmax/cm 1708, 1618, 1532, 1482, 1418, 1353,
325, 1303, 1085, 922, 777, 720, 705.
REFERENCES
1
. Zhou, T.; Chen, Z.-C. Hypervalent Iodine in Synthesis 79: Reductive
Homocoupling of Diaryliodonium Salts in the Presence of Palladium
Catalyst and Indium. J. Chem. Res(S) 2001, 153.
2
3
4
5
6
. The Merck Index, tenth Edn., P157, 1101.
. Ryang, M.; Tsutsumi, S. Bull. Chem. Soc. Jpn. 1962, 35, 1121.
. Stephen, H. J. Chem. Soc. 1920, 117, 510.
. Morley, J.O. Synthesis 1977, 54.
. Sandin, R.B.; Melby, R.; Crawford, R.; McGreer, D. J. Am. Chem. Soc.
1956, 78, 3817. CA 1957, 51, 339b.
7. Larock, R.C.; Hershberger, S.S. J. Org. Chem. 1980, 45, 3840.
Received in Japan June 18, 2001

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