Palladium(II)- and rhodium(III)-catalyzed carbonylation reaction of aryltin compounds

Article abstract of DOI:10.1246/bcsj.74.1343

The Pd(II)- and Rh(III)-catalyzed carbonylation reaction of several aryltin compounds, i.e., tetraphenyltin (Ph₄Sn), in acetonitrile (MeCN) and acetic acid was studied. The reaction of Ph₄Sn with 1 atm of CO in the presence of a stoichiometric amount of Pd(II) salt was performed to confirm whether more than one of the four phenyl groups could be transferred to the products. To accelerate the carbonylation, LiCl was added, thus, producing benzophenone, benzoic acid, and a small amount of biphenyl as organic products, but only one of the four phenyl groups was transferred to the products. For the Rh(II)-mediated and -catalyzed carbonylation of aryltin compounds in MeCN, benzophenone was mainly produced together with benzoic acid and biphenyl. Seventy-five percent of the four phenyl groups were transferred to the products. The product yield was > 100% based on the amount of Rh(III) chloride used, showing that the Rh(III) salt itself worked as a catalyst without reoxidant addition. Thus, More than one of two, three, or four aryl groups of aryltin compounds, and almost all of them in some cases, could be transferred to the products in this catalytic carbonylation.

Full text of DOI:10.1246/bcsj.74.1343

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
c. Jpn.
© 2001 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 74, 1343–1348 (2001) 1343
e Chemical
ciety of Ja-
n
e Chemical
ciety of Ja-
n
Palladium(Ⅱ)- and Rhodium(Ⅲ)-Catalyzed Carbonylation Reaction of
Aryltin Compounds
Pd(Ⅱ)- and Rh(Ⅲ)-Catalyzed Carbonylation
T. Ohe et al.
Toshiyuki Ohe, Shin-ichi Motofusa, Kouichi Ohe, and Sakae Uemura*
01
43
48
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University,
Sakyo-ku, Kyoto 606-8501
SJA8
09-2673
050
(Received February 13, 2001)
bruary
A variety of aryltin compounds can be employed for carbonylation reactions in the presence of a catalytic amount
of palladium(Ⅱ) salt with reoxidant in acetonitrile or acetic acid under an atmospheric pressure of carbon monoxide (CO)
to afford arenecarboxylic acids and diaryl ketones. Similar reactions also proceed by using rhodium(Ⅲ) salt as a catalyst,
where the presence of reoxidant is sometimes not necessary. More than one of two, three, or four aryl groups of aryltin
compounds, and almost all of them in some cases, can be transferred to the products in this catalytic carbonylation.
01
01
0
Organic transformations using organotin compounds have
been powerful tools for organic synthesis in the last two de-
cades.1 Many examples of the conversion of C–Sn bond to C–
C bond have been reported, such as Pd(0)-catalyzed cross cou-
pling reaction with organic halides or acyl halides (the so-
called Stille cross coupling),1 Lewis acid-mediated or transi-
tion metal-catalyzed 1,2-addition reaction to carbonyl com-
pounds and imines,2 Heck-type dehydroarylation reaction of
α,β-unsaturated carbonyl compounds,3 Michael-type hydro-
arylation reaction of α,β-unsaturated carbonyl compounds,4
organic transformations including radical intermediates,5 and
so on. The carbonylation reactions of organotin compounds
with carbon monoxide (CO) have been investigated for these
three decades including Stille carbonylative cross coupling,1,6
but there are only very few examples of simple carbonylation
as far as we know.7 In these reactions it was so far thought that
at most only one of four organic groups of tetraorganotin com-
pounds can be transferred to the products. However, the inves-
tigation to utilize more than one organic group of organohet-
eroatom compounds for organic reactions is of current interest
from the viewpoint of atom economy.8 Actually, it has recently
been disclosed that almost all organic groups can be utilized
for some reactions, including our recent report of Pd-catalyzed
Michael-type hydroarylation reaction using aryltin com-
pounds.4d As one of our series of studies of C–C bond forming
reactions using organoheteroatom (B,9 Sb,10 Bi,11 Sn4d) com-
pounds, we have now examined simple carbonylation reactions
of tetra- to di-aryltins in detail from the viewpoint of atom
economy of aryl groups. As a result, we found that more than
one aryl group, and sometimes almost all of them, were trans-
ferred to the products, arenecarboxylic acids and diaryl ke-
tones, in the presence of either a stoichiometric or a catalytic
amount of Pd(Ⅱ) or Rh(Ⅲ) salt together with a suitable reoxi-
dant in acetonitrile (MeCN) or acetic acid (AcOH). We report
here the details of results of this carbonylation.
tin Compounds in MeCN. At first, we carried out the reac-
tion of tetraphenyltin (Ph4Sn) with an atmospheric pressure of
CO in the presence of a stoichiometric amount of Pd(Ⅱ) salt in
order to confirm whether more than one of the four phenyl
groups could be transferred to the products. Thus, a mixture of
Ph4Sn (0.5 mmol), PdCl2 (0.5 mmol), and LiCl (4 mmol) was
stirred in MeCN (5 mL) under CO (1 atm, 1 atm = 1.01325 ×
105 Pa) at 25 °C for 20 h. The reason for the addition of LiCl
was to accelerate the carbonylation, as in the case of Michael-
type hydroarylation reaction.4d,12 As a result, benzophenone
was mainly obtained together with benzoic acid and a small
amount of biphenyl as organic products, but only one of the
four phenyl groups was transferred to the products (Eq. 1; Ta-
ble 1, Entry 1).
Pd salt
(1)
Ph4Sn CO (1 atm), MeCN→ PhCO2H+ PhCOPh+ Ph – Ph
25 °C, 20 h
As the stoichiometry for the formation of benzophenone and
benzoic acid (benzoyl chloride is a precursor which is hydro-
lyzed to the acid by the work-up procedure) can be described
as Eq. 2 and 3, respectively, it was thought that proper amounts
of PdCl2 to transfer all phenyl groups to the products are four-
fold molar ones of Ph4Sn.
Table 1. Carbonylation of Ph4Sn in Presence of Stoichio-
metric Amount of Pd Salt in MeCN*
Pd salt
Additive
Isolated yield/%a)
Entry
mmol
PdCl2(0.5)
PdCl2(2)
PdCl2(2)
Na2PdCl4(0.5)
Na2PdCl4(2)
mmol
LiCl(4)
LiCl(4)
LiCl(8)
—
PhCO2H
PhCOPh
Ph–Ph
1
2
3
4
5
7
10
11
7
22
73
81
17
85
6
0
0
4
0
—
12
*CO (1 atm) and MeCN (5 mL) were used.
a) Based on Ph4Sn employed (0.5 mmol): 2 mmol of
PhCO2H, 1 mmol of PhCOPh, and 1 mmol of Ph–Ph corre-
spond to 100% yield, respectively.
Results and Discussion
Pd(Ⅱ)-Mediated and -Catalyzed Carbonylation of Aryl-

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
1344 Bull. Chem. Soc. Jpn., 74, No. 7 (2001)
Pd(ꢀ)- and Rh(ꢁ)-Catalyzed Carbonylation
Table 2. Pd(Ⅱ)-Catalyzed Carbonylation of Aryltin Compounds in MeCN*
ArnSnCl(4−n)
mmol
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
(p-CH3C6H4)4Sn(0.5)
(p-CH3OC6H4)4Sn(0.5)
(p-ClC6H4)4Sn(0.5)
Ph3SnCl(0.67)
Ph2SnCl2(1.0)
PhSnCl3(2.0)
PdCl2
Reoxidant
mmol
—
Isolated yield/%a)
Entry
mmol
0.1
0.1
0.1
0.02
0.1
0.1
0.1
0.1
0.1
ArCO2H ArCOAr Ar–Ar
b)
1
2
3
4
5
6
7
8
9
4
30
57
23
23
58
66
43c)
66
84
85
86
1
1
2
7
< 1
0
CuCl2(4)b)
CuCl2(4)
CuCl2(4)
CuSO4(4)b)
CAN(2)
< 1
24
40
< 1
< 1
< 1
5
5
1
2
6
< 1
< 1
5
3
4
CuCl2(4)
CuCl2(4)
CuCl2(4)
CuCl2(4)
CuCl2(4)
CuCl2(4)
10
11
12
0.1
0.1
0.1
3
2
*CO (1 atm) and MeCN (5 mL) were used.
a) Based on ArnSnCl(4−n) employed (2 mmol as Ar group): 2 mmol of ArCO2H, 1 mmol of
ArCOAr, and 1mmol of Ar–Ar correspond to 100% yield, respectively. b) LiCl (4 mmol) was
added. c) C6H5OCH3(24% GLC yield) was also obtained.
Ph4Sn + 2PdCl2 + 2CO → 2PhCOPh + SnCl4+2Pd
Ph4Sn + 4PdCl2 + 4CO → 4PhCOCl + SnCl4+4Pd
(2)
(3)
oxidants were ineffective (Table 2, Entries 5 and 6). The Pd(0)
compound [Pd2(dba)3] did not work as a catalyst.
In a similar treatment of other tetraaryltin compounds
(Ar4Sn) such as (p-CH3C6H4)4Sn, (p-CH3OC6H4)4Sn, and (p-
ClC6H4)4Sn in PdCl2/CuCl2 system, between two and three
aryl groups out of the four aryl groups of Ar4Sn could also be
transferred to the products (Table 2, Entries 7–9). The maxi-
mum turnover number to palladium in these carbonylations
was 13.7 (1.32 mmol of arenecarboxylic acid and 0.05 mmol
of diaryl ketone were obtained using 0.1 mmol of PdCl2; Table
2, Entry 9).
Carbonylation could also be applied to phenyltin chlorides
such as Ph3SnCl, Ph2SnCl2, and PhSnCl3. Thus, treatment of
PhnSnCl(4−n)[2 mmol as phenyl group(s); i.e. 0.67 mmol of
Ph3SnCl, 1 mmol of Ph2SnCl2, and 2 mmol of PhSnCl3, re-
spectively] with CO (1 atm) in the presence of PdCl2 (0.1
mmol) and CuCl2 (4 mmol) as the reoxidant in MeCN (5 mL)
at 25 °C for 20 h afforded almost exclusively benzoic acid,
where slightly fewer than all phenyl groups were utilized in all
cases (Table 2, Entries 10–12), the turnover number to palladi-
um in these cases being more than 17.
Then, Ph4Sn (0.5 mmol) was treated with CO in the pres-
ence of four-fold molar amounts of PdCl2 (2.0 mmol; equimo-
lar amounts to C–Sn bonds) and LiCl (4–8 mmol). The prod-
ucts were again benzophenone and benzoic acid together with
a precipitation of palladium black, and in this case almost all
phenyl groups were transferred to the products as expected
(Table 1, Entries 2 and 3). This result shows that four phenyl
groups of Ph4Sn can be utilized for the carbonylation reaction
under an atmospheric pressure of CO. The stoichiometric re-
action using Na2PdCl4 instead of PdCl2 and LiCl gave similar
results (Table 1, Entries 4 and 5).
We next investigated the carbonylation of various aryltin
compounds using a catalytic amount of Pd(Ⅱ) salt together
with a variety of reoxidants, such as CuCl2, CuSO4, Cu(OAc)2,
NaBrO3, Na2S2O8, p-benzoquinone (C6H4O2), CAN[Ce-
(NH4)2(NO3)6], AgOAc, H2O2, I2, and air, by considering reox-
idation of Pd(0) to Pd(Ⅱ) (Eq. 4).
Rh(Ⅲ)-Mediated and -Catalyzed Carbonylation of Aryl-
tin Compounds in MeCN. Similar carbonylation was next
carried out using Rh(Ⅲ) salt in place of Pd(Ⅱ) salt. When
Ph4Sn (0.5 mmol) was treated with CO (1 atm) in MeCN (5
cat. PdCl2 , Reoxidant
ArnSnCl(4−n) CO (1 atm), MeCN→ ArCO2H+ ArCOAr + Ar – Ar
25 °C, 20 h
(4)
mL) in the presence of
a stoichiometric amount of
Thus, Ph4Sn (0.5 mmol) was treated with CO (1 atm) in the
presence of PdCl2 (0.02–0.1 mmol) and one of these reoxi-
dants with or without LiCl in MeCN (5 mL) at 25 °C for 20 h.
As a result, the system using PdCl2 and CuCl2 (4 mmol, 8 mo-
lar equivalents to Ph4Sn) without LiCl was revealed to be most
efficient; between two and three out of the four phenyl groups
of Ph4Sn were transferred to the products, as shown in Table 2,
Entries 1–3. The amount of PdCl2 could be lowered to 0.02
mmol (0.04 molar amount to Ph4Sn, and 0.01 molar amount to
each C–Sn bond) where almost two out of the four phenyl
groups were transferred to the products (Table 2, Entry 4). The
reoxidants CuSO4 and CAN were also effective, but other re-
RhCl3•3H2O (0.5 mmol), benzophenone was mainly produced
together with benzoic acid and biphenyl (Eq. 5).
Rh salt
ArnSnCl(4−n) CO (1 atm), MeCN→ ArCO2H+ ArCOAr + Ar – Ar
25 °C, 20 h
(5)
Here, three fourths of the four phenyl groups were tran-
ferred to the products as shown in Table 3, Entry 1. Interest-
ingly, the product yield (1.17 mmol of carbonylated products)
is higher than 100% based on the amount of Rh(Ⅲ) chloride
used, showing that the Rh(Ⅲ) salt itself worked as a catalyst

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
T. Ohe et al.
Bull. Chem. Soc. Jpn., 74, No. 7 (2001) 1345
Table 3. Rh(Ⅲ)-Catalyzed Carbonylation of Aryltin Compounds in MeCN*
ArnSnCl(4−n)
mmol
Rh species
Isolated yield/%a)
Entry
mmol
ArCO2H ArCOAr Ar–Ar
1
2
3
4
5
6
7
Ph4Sn(0.5)
Ph4Sn(0.5)
RhCl3•3H2O(0.5)
RhCl3•3H2O(0.1)
RhCl3•3H2O(0.5)
RhCl3•3H2O(0.5)
RhCl3•3H2O(0.5)
RhCl3•3H2O(0.5)
[RhCl(CO)2]2(0.05)
21
13
10
16
14
4
75
29
64
38
41
57
10
< 1
< 1
4
9
3
Ph3SnCl(0.67)
Ph2SnCl2(1.0)
(p-CH3C6H4)4Sn(0.5)b)
(p-ClC6H4)4Sn(0.5)
Ph4Sn(0.5)
7
< 1
9
*CO (1 atm) and MeCN (5 mL) were used.
a) Based on ArnSnCl(4−n) employed (2 mmol as Ar group): 2 mmol of ArCO2H, 1 mmol of
ArCOAr, and 1 mmol of Ar–Ar correspond to 100% yield, respectively. b) MeCN (20 ml) was
used.
without the addition of reoxidant.7b Similarly, by use of 0.1
Table 4. Pd(Ⅱ)-Catalyzed Carbonylation of Aryltin
Compounds in AcOH*
mmol of RhCl3•3H2O, 0.55 mmol of carbonylated compounds
were produced (Table 3, Entry 2). Different from the Pd(Ⅱ)
cases, the addition of oxidant such as CuCl2 or Na2S2O8 almost
stopped the reaction. Results of carbonylation of several aryl-
tin compounds are also shown in Table 3 (Entries 3–6), where
a half and three fourths of two and three aryl groups were
transferred, respectively, to the products. It is worth noting
that Rh(Ⅰ) salt such as rhodium(Ⅰ) chlorocarbonyl complex also
worked as a catalyst (Table 3, Entry 7).
Aryltins
Entry
Isolated yield/%a)
mmol
ArCO2H
ArCOAr
11
Ar–Ar
< 1
1
< 1
< 1
< 1
3
1
2
Ph4Sn(0.5)
65
20
56
3c)
36
54
62
31
3
Ph4Sn(0.5)b)
17
6
7
39
31
16
2
3
4
5
6
(p-CH3C6H4)4Sn(0.5)
(p-CH3OC6H4)4Sn(0.5)
(p-CIC6H4)4Sn(0.5)
Ph3SnCl(0.67)
7
Ph2SnCl2(1.0)
5
2
5
Pd(Ⅱ)-Catalyzed Carbonylation of Aryltin Compounds
in AcOH. Palladium(Ⅱ)-catalyzed carbonylation of various
aryltin compounds using a system of PdCl2/CuCl2 was next
carried out in AcOH in which a high efficiency of atom trans-
fer has been observed in Pd(Ⅱ)-catalyzed Michael-type hy-
droarylation of α,β-unsaturated carbonyl compounds with
Ph4Sn.4d When Ph4Sn (0.5 mmol) was treated with CO (1 atm)
in the presence of PdCl2 (0.1 mmol)/CuCl2 (4 mmol) in AcOH
(5 mL) at 25 °C for 20 h, benzoic acid was mainly produced,
together with benzophenone and a trace amount of biphenyl
(Eq. 6; Table 4, Entry 1) where about three out of four phenyl
groups were transferred to the products.
8
9
10
11
12
PhSnCl3(2.0)
PhSnBu3(2.0)
p-CH3C6H4SnBu3(2.0)
p-CH3OC6H4SnBu3(2.0)
p-ClC6H4SnBu3(2.0)
53d)
47d)
21e)
45d)
< 1
0
2
3
f)
—
4
*PdCl2 (0.1 mmol), CuCl2 (4 mmol), CO (1 atm) and
AcOH (5 mL) were used.
a) Based on aryltin compound employed (2 mmol as Ar
group): 2 mmol of ArCO2H, 1 mmol of ArCOAr, and 1
mmol of Ar–Ar correspond to 100% yield, respectively. b)
CuCl2 2 mmol. c) C6H5OCH3 (42% GLC yield) was also
formed. d) A small amount of chlorinated arene (ArCl) was
also formed. e) C6H5OCH3 (63% GLC yield) and p-
CH3OC6H4Cl (8% GLC yield) were also formed. f) Not
determined.
cat. PdCl2 , CuCl2
ArnSnY
(
→ ArCO2H+ ArCOAr + Ar – Ar
(4−n)
CO (1 atm), AcOH
Y= Cl, 1ꢀn ꢀ4
Y= Bu, n=1
25 °C, 20 h
)
(6)
product yield. In AcOH as solvent, however, we found that
several reoxidants worked well in rhodium(Ⅲ)-catalyzed car-
bonylation (Eq. 7).
Other reoxidants such as CuCl2•2H2O, CuSO4, and CAN
could also be used, but they were less effective. Carbonylation
could be applied to various tetraaryltins (Table 4, Entries 3–5)
as well as phenyltin compounds (Table 4, Entries 6–8) with a
good atom economy of aryl groups in all cases except the case
of tetrakis(p-methoxyphenyl)tin (Table 4, Entry 4) where ani-
sole, a protodestannylation compound,13 was the major prod-
uct. In the cases of aryltributyltins, the corresponding diaryl
ketone became the main product (Table 4, Entries 9–12). The
maximum turnover number to palladium was 14.1 (1.30 mmol
of arenecarboxylic acid and 0.11 mmol of diaryl ketone were
obtained using 0.1 mmol of PdCl2; Table 4, Entry 1).
cat. Rh salt, Reoxidant
ArnSnCl(4−n) CO (1 atm), AcOH→ ArCO2H+ ArCOAr + Ar – Ar
25 °C, 20 h
(7)
The carbonylation of Ph4Sn in the presence of RhCl3•3H2O
(0.1 mmol) afforded mainly benzoic acid (22%, 0.44 mmol)
together with benzophenone (8%, 0.08 mmol) and a small
amount of biphenyl (1%, 0.01 mmol) (Table 5, Entry 1). Here,
it was also shown that the total amounts of these products were
larger than the amount of RhCl3•3H2O employed, and that
slightly more than one of four phenyl groups could be utilized
for the carbonylation reaction. Addition of reoxidants such as
Cu(OAc)2 and AgOAc increased the product yield, as shown in
Rh(Ⅲ)-Catalyzed Carbonylation of Aryltin Compounds
in AcOH. As described above, RhCl3•3H2O itself worked as
a catalyst without any reoxidant in the carbonylation reaction
of Ph4Sn in MeCN; the addition of reoxidant decreased the

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
1346 Bull. Chem. Soc. Jpn., 74, No. 7 (2001)
Pd(ꢀ)- and Rh(ꢁ)-Catalyzed Carbonylation
Table 5. Rh(Ⅲ)-Catalyzed Carbonylation of Aryltin Compounds in AcOH*
ArnSnCl(4−n)
mmol
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph4Sn(0.5)
Ph3SnCl(0.67)
Ph2SnCl2(1.0)
Ph3SnCl(0.67)
Ph2SnCl2(1.0)
(p-CH3C6H4)4Sn(0.5)
(p-CH3OC6H4)4Sn(0.5)
(p-CIC6H4)4Sn(0.5)
PhSnBu3(2.0)
Rh speciesa)
Reoxidant
Isolated yield/%b)
Entry
mmol
mmol
—
Cu(OAc)2(2)
CuSO4(4)
CuCl2(4)
AgOAc(4)
—
Cu(OAc)2(4)
Cu(OAc)2(2)
Cu(OAc)2(2)
Cu(OAc)2(4)
Cu(OAc)2(4)
Cu(OAc)2(4)
Cu(OAc)2(4)
Cu(OAc)2(4)
Cu(OAc)2(4)
ArCO2H ArCOAr Ar–Ar
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
RhCl3•3H2O(0.1)
RhCl3•3H2O(0.1)
RhCl3•3H2O(0.1)
RhCl3•3H2O(0.1)
RhCl3•3H2O(0.1)
“Rh3O”(0.034)
“Rh3O”(0.034)
RhCl3•3H2O(0.1)
RhCl3•3H2O(0.1)
“Rh3O”(0.034)
“Rh3O”(0.034)
“Rh3O”(0.034)
“Rh3O”(0.034)
“Rh3O”(0.034)
“Rh3O”(0.034)
22
75
33
< 1
43
20
71
41
0
8
2
2
< 1
< 1
1
1
3
< 1
4
1
< 1
< 1
< 1
< 1
7
< 1
6
< 1
6
41
16
68
< 1
1
1
4
1
4
3
27c)
57
12
2
< 1
< 1
*CO (1 atm) and AcOH (5 mL) were used.
a) “Rh3O” W [Rh3O(OAc)6(H2O)3]OAc. b) Based on ArnSnCl(4−n) employed (2 mmol as Ar group): 2 mmol of
ArCO2H, 1 mmol of ArCOAr, and 1 mmol of Ar–Ar correspond to 100% yield, respectively. c) C6H5OCH3(26%
GLC yield) was also formed.
Table 5, Entries 2 and 5, respectively. In this case, however,
CuCl2 stopped the reaction (Table 5, Entry 4), probably be-
cause this carbonylation disfavors the presence of excess chlo-
ride anions as the addition of LiCl also stopped the reaction
completely. As one chloride-free rhodium(Ⅲ) salt, we noticed
oxo-centered trinuclear rhodium(Ⅲ) acetate {[Rh3O(OAc)6-
(H2O)3]OAc}14 which was actually effective as a catalyst (Ta-
ble 5, Entries 6 and 7). Carbonylation of other tetraaryltins
than Ph4Sn in the presence of RhCl3•3H2O almost failed, while
the Rh(Ⅲ) acetate was shown to be effective (Table 5, Entries
12–14). Results of the application to various aryltin com-
pounds using this acetate are shown in Table 5. The maximum
turnover number to rhodium was 15.2 (1.50 mmol of benzoic
acid and 0.02 mmol of benzophenone were obtained; Table 5,
Entry 2). The characteristic feature in Rh(Ⅲ)-catalyzed carbo-
nylation is that arenecarboxylic acid is almost the sole product,
in contrast to similar reactions in MeCN where diaryl ketone is
Scheme 1. Plausible reaction scheme.
the major product.
Plausible Reaction Scheme. We propose the reaction
pathway for this catalytic carbonylation reaction as shown in
Scheme 1. The transmetallation of Sn(Ⅳ) moiety of aryl-
tin(Ⅳ) compounds by palladium(Ⅱ) salt [A: X = Cl or OAc]
occurs to give an Ar–Pd–X species (B), to which CO coordi-
nates to afford a metal carbonyl species (C). Then, this carbo-
nyl species gives an acylpalladium(Ⅱ) species (D) to which the
other organotin(Ⅳ) compound attacks to afford an acylarylpal-
ladium species (E), which gives diaryl ketone and Pd(0) spe-
cies by reductive elimination. Palladium(0) is oxidized by the
oxidant such as Cu(Ⅱ) salt to regenerate the species A. Reduc-
tive elimination from the species D might give acyl chloride
(in MeCN) or unsymmetrical acid anhydride (in AcOH) (ab-
breviated to ArCOX), followed by aqueous work-up to give
arenecarboxylic acid: this expectation is based on the forma-
tion of arenecarboxamide when NH4Cl was added under in-
complete hydrolysis (see Experimental). The second transmet-
allation of Sn(Ⅳ) moiety of aryltin(Ⅳ) compounds by the spe-
cies B occurs to give Ar–Pd(Ⅱ)–Ar species (F), reductive elim-
ination from which gives biaryl. A similar reaction pathway
can be considered to occur in Rh(Ⅲ)-catalyzed carbonylation
in AcOH. Partially dearylated aryltins (XSnR3) produced by
the first cycle also enter this catalytic cycle, resulting in the
transfer of more than one aryl group to products.
In the case of carbonylation using Rh(Ⅲ) chloride in MeCN,
a pathway of oxidative addition of aryltin(Ⅳ) compounds to
the produced Rh(Ⅰ) species to generate Ar–Rh(Ⅲ)–SnR3 spe-
cies might be considered, though the details are not yet clear.
The formation of a small amount of chlorinated arene (Ar–
X) from the carbonylation of ArSnBu3 may be explained by re-
ductive elimination of Pd(0) from the species B.
Experimental
General Procedure. Melting points were determined on a
Yanako MP-J3 micro melting point apparatus and are uncorrected.