Hypervalent iodine in synthesis. Part XXIX: Palladium-catalyzed carbonylation of diaryliodonium salts by chloroform and alkali

Article abstract of DOI:10.1039/a900126c

Diaryliodonium salts are catalytically carbonylated by CO generated in situ from chloroform and aqueous alkali in the presence of (Ph₃P)₂PdCl₂ in good yields under N₂ at 50°C.

Full text of DOI:10.1039/a900126c

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328 J. CHEM. RESEARCH (S), 1999
J. Chem. Research (S),
1999, 328^329y
Hypervalent Iodine in Synthesis. Part XXIX:
Palladium-catalyzed Carbonylation of
Diaryliodonium Salts by Chloroform and Alkaliy
Min Xia and Zhen-Chu Chen*
Department of Chemistry, Hangzhou University, Hangzhou, 310028, P.R. China
Diaryliodonium salts are catalytically carbonylated by CO generated in situ from chloroform and aqueous alkali in the
presence of ꢀPh3P†2PdCl2 in good yields under N2 at 50 8C.
The transition metal-catalyzed carbonylation of various
organic substrates is of signi¢cant importance in organic
synthesis. A great variety of inexpensive, simple, and highly
e¤cient carbonylations have been observed,1 and particular
interest would be the carbonylation of organic halides.
Recently, Grushin and Alper reported a novel method for
the preparation of aromatic carboxylic acids from iodoarenes
by palladium-catalyzed carbonylation with chloroform and
alkali.2 Although the reaction is very simple, clear and con-
venient, without requiring toxic and dangerous carbon
monoxide as participant, its overall timescale limits its appli-
cation.
Recent developments in hypervalent iodine chemistry have
shown that organoiodine(III) compounds are good substitutes
for organic halides in most cases due to their high reactivity
which leads to improvements in many reactions.3 In connec-
tion with our programs to utilize hypervalent iodine com-
pounds in organic synthesis,4 we have investigated the
carbonylation of diaryliodonium salts with chloroform and
alkali. Here we report the results which are summarized
in Scheme 1 and Table 1.
salts containing various substituents such as methyl,
methoxyl, chloro, bromo and nitro groups, were successfully
carbonylated with chloroform and alkali. Additionally, the
reaction can be carried out readily not only for symmetric
iodonium salts but also for unsymmetric iodonium salts
which produce single products with elimination of
iodobenzene as expected. Under similar conditions,
phenylethynylphenyliadonium salt also reacts with chloroform
and alkali in the presence of catalytic amounts of
ꢀPh3P†2PdCl2 to give 3-phenylpropynoic acid (Table 1, entry
9).
A
plausible mechanism for the palladium-catalyzed
carbonylation of diaryliodonium salts by chloroform and
alkali is analogous to that of iodoarenes and is shown in
Scheme 2.
ArCO2– + H2O + X – + ArI
2OH – + Ar2I +X –
OH –
–
CCl3
L2Pd(X)(Ar)
CCl3H
Cl –
L2(X)ArPd=CCl2
2OH –
L2Pd(X)(COAr)
i, 5%(Ph3P)2PdCl2, aq. KOH, 50 ˚C
ArI +ArX – + CHCl3
ArCO2H
ii, H3+O
L2Pd(X)Ar(CO)
2Cl – + H2O
Scheme 1
Scheme 2 L ˆ PPh3.
We have found that palladium-catalyzed carbonylation of
diaryliodonium salts with chloroform and alkali takes place
smoothly, reaching completion within 1h at 50 8C.
Chloroform can be used in a large excess acting as both
the reagent and the organic phase. Several diaryliodonium
In conclusion, we describe a simple, e¤cient method for
the palladium-catalyzed carbonylation of diaryliodonium
salts by chloroform and alkali, which may be a valuable
alternative to that of iodoarenes.
Ta b l e 1 Palladium-catalyzed carbonylation of diaryliodonium salts by chloroform and alkali
Entry
Substrate
Producta
Yield(%)b
Mp/ 8C
Mp Lit./8C
‡
1
2
3
4
5
6
7
8
9
Ph2I Cl
PhCO2H
70
64
78
74
72
41
67
77
61
54
110^112
179^181
182^184
235^237
250^252
137^139
178^180
182^184
132^134
126^128
1125
‡
ꢀp-MeC6H4†2I I
p-MeC6H4CO2H
p-MeOC6H4CO2H
p-ClC6H4CO2H
p-BrC6H4CO2H
m-O2NC6H4CO2H
p-MeC6H4CO2H
p-MeOC6H4CO2H
PhCꢁCCO2H
1816
‡
ꢀp-MeOC6H4†2I I
1847
‡
‡
ꢀp-ClC6H4†2I Cl
237^2398
251^2539
139^14210
1816
ꢀp-BrC6H4†2I CI
‡
ꢀm-O2NC6H4†2I Cl
‡
ꢀp-MeC6H4I PhBr
‡
ꢀp-MeOC6H4I PhBr
1847
‡
PhCꢁCl PhOTs
135^13711
129^13012
10
S
I+PhOTs
S
CO2H
a All of the products were identified by comparison of their melting point with authentic samples. b After purification by recrystallization.
* To receive any correspondence.
Experimental
y This is a Short Paper as de¢ned in the Instructions for Authors,
General Procedureforthe Carbonylation of Iodonium Salts withCHCl3
and Alkali.öTo a degassed mixture of 60% aqueous KOH (5 g), CHCl3
(1ml) and iodonium salt (1ml) in a 5 ml Schlenk £ask was added
Section 5.0 [see J. Chem. Research (S), 1999, Issue 1]; there is
therefore no corresponding material in J. Chem. Research (M).
Part XXVIII: ref. 4.

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J. CHEM. RESEARCH (S), 1999 329
ꢀPh3P† PdCl2 (0.05 mmol) and the biphasic mixture was vigorously
stirred2at 50 8C under N2 until the solid iodonium salt disappeared
(usually within 1h). Water (10 ml) and ether (10 ml) were added, the
aqueous layer was separated, acidi¢ed with 20% HCl and extracted
with ether ꢀ2 Â 10 ml).The combined ether layers were dried with anhy-
drous MgSO4, ¢ltered and evaporated to give the product, which was
puri¢ed by recrystallization.The acids were found to be pure and ident-
ical (melting point) with authentic samples.
3
R. M. Moriarty, W. R. Epa and A. K. Awasthi, J. Am. Chem.
Soc., 1991, 113, 6315; R. M. Moriarty and W. R. Epa,
Tetrahedron Lett., 1992, 33, 4095; R. J. Hinkle, G. T. Poulter
and P. J. Stang, J. Am. Chem. Soc., 1993, 115, 11626; S.
K. Kang, K. Y. Jung, C. H. Park and S. B. Jang, Tetrahedron
Lett., 1995, 36, 8047; S. K. Kang, H. W. Lee, S. B. Jang,
T. H. Kim and S. J. Pyun, J. Org. Chem., 1996, 61, 2604;
S. K. Kang, T. Yamahuchi, T. H. Kim and P. S. Ho, J. Org.
Chem., 1996, 61, 9082; S. K. Kang, H. W. Lee, W. K. Choi,
R. K. Hong and J. S. Kim, Synth. Commun., 1996, 26, 4219.
Hypervalent Iodine in Synthesis XXVIII: The Preparation and
Utilization of Polymer-Supported Phenyliodine(III) Diacetate,
G. P. Wang and Z. C. Chen, Synth. Commun., 1999, in press.
The Merck Index, 10th edn., no. 1093.
We are grateful for ¢nancial support from the National
Science Foundation of China (Project 29472036).
4
Received, 5th January 1999; Accepted, 4th February 1999
Paper E/9/00126C
5
6
7
The Merck Index, 10th edn., no. 9363.
H. Gilman, W. Langham and H. B. Willis, J. Am. Chem. Soc.,
1940, 62, 346.
8
9
F. E¡enberger and P. Gleiter, Chem. Ber., 1964, 97, 480.
The Merck Index, 10th. edn., no. 1378.
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