Palladium-catalyzed C-phenylation of methyl acrylate with triphenylbismuth dicarboxylates

Article abstract of DOI:10.1007/s11176-005-0507-4

A new catalytic reaction of C-phenylation of methyl acrylate with bismuth derivatives Ph₃Bi(O₂CR)₂ (R = H, Me, Et, Bu, CF₃, Ph) or Ph₃BiCl₂ in a 3 : 1 ratio was studied. The reaction was performed in the presence of 4 mol % palladium compounds PdCl₂, Pd(OAc)₂, Pd₂(dba) ₃, Pd(Ph₃P)₂Cl₂, and PdLCl ₂ (L = dppm, dppe, dppp, dppb, dppf, binap, xantphos) at 50°C in CH₃CN, DMF, THF, or CH₂Cl₂ and gave methyl cinnamate (yield up to 85% based on the starting bismuth compound), diphenyl (up to 138%), and benzene (up to 59%).

Full text of DOI:10.1007/s11176-005-0507-4

Russian Journal of General Chemistry, Vol. 75, No. 11, 2005, pp. 1766 1770. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 11, 2005,
pp. 1849 1853.
Original Russian Text Copyright
2005 by Malysheva, Moiseev, Gushchin, Dodonov.
Palladium-Catalyzed C-Phenylation of Methyl Acrylate
with Triphenylbismuth Dicarboxylates
Yu. B. Malysheva, D. V. Moiseev, A. V. Gushchin, and V. A. Dodonov
Lobachevsky Nizhni Novgorod State University, Nizhni Novgorod, Russia
Received October 22, 2004
Abstract A new catalytic reaction of C-phenylation of methyl acrylate with bismuth derivatives
Ph Bi(O CR) (R = H, Me, Et, Bu, CF , Ph) or Ph BiCl in a 3 : 1 ratio was studied. The reaction was
3
2
2
3
3
2
performed in the presence of 4 mol % palladium compounds PdCl , Pd(OAc) , Pd (dba) , Pd(Ph P) Cl , and
2
2
2
3
3
2
2
PdLCl (L = dppm, dppe, dppp, dppb, dppf, binap, xantphos) at 50 C in CH CN, DMF, THF, or CH Cl and
2
3
2
2
gave methyl cinnamate (yield up to 85% based on the starting bismuth compound), diphenyl (up to 138%),
and benzene (up to 59%).
Organobismuth compounds are mild reagents for
formation of C C bonds in reactions with phenols,
enols, -diketones, and -keto esters [1, 2]. C-Phenyl-
ation of unsaturated compounds with bismuth deriva-
tives was performed for the first time by Asano [3].
In that study, styrene was converted into stilbene by
The resulting bismuth derivatives were used for
C-phenylation of methyl acrylate in the presence of
catalytic amounts of palladium. The reaction of tri-
phenylbismuth dipropionate with methyl acrylate I
was performed in the presence of catalytic amounts
of PdCl in acetonitrile at 50 C for 3 h. The reactant
2
the reaction with Ph Bi in the presence of a stoichio-
ratio was Ph Bi(O CEt) : I : PdCl = 1 : 3 : 0.04.
3
3
2
2
2
metric amount of Pd(OAc) at 50 C. The same system
was later used for phenylation of octene, ethyl acrylate
Ph Bi(O CEt) was chosen as the starting organome-
2
3 2 2
tallic compound taking into account high phenylating
activity of the corresponding antimony derivative
under similar conditions [11, 12]. Methyl acrylate I is
a convenient model compound. It is very reactive and
is selectively phenylated at the trans position to meth-
yl cinnamate II. Ester I was taken in a threefold excess
relative to the organometallic compounds, because all
the three phenyl groups in triphenylbismuth dicarbox-
ylate can be involved in the reaction:
[
4], and methyl acrylate [5]. The interest in couplings
of organobismuth compounds in the presence of cata-
lytic amounts of palladium compounds recently in-
creased. Among such reactions are C-phenylation of
alkenes with bismuthonium salts [6] or diphenylbis-
muth chloride [7] and carbonylation of triphenylbis-
muth to obtain ketones [8]. In all the coupling reac-
tions, diphenyl was formed in significant amounts
as by-product. The homocoupling of organometallic
compounds of Bi(III, V) to diaryls in the presence of
palladium compounds was specially studied in [9, 10].
Ph Bi(O CEt) + CH =CHCO Me
3
2
2
2
2
I
PdCl2
PhCH=CHCO Me + Ph + PhH.
2
2
We found recently that triarylantimony dicarbox-
ylates are efficient and mild agents for C-arylation of
unsaturated compounds. In an argon atmosphere, one
phenyl group is transferred to the unsaturated com-
pound, and in an oxygen atmosphere, two phenyl
groups are transferred [11, 12]. Proceeding with these
studies, we tested in similar reactions triphenylbis-
muth dicarboxylates and compared them with the cor-
responding antimony derivatives. For this purpose, we
prepared the compounds Ph BiX in one step by the
CH3CN
II
III
IV
We obtained the following phenyl-containing com-
pounds: methyl cinnamate II (cross-coupling product,
yield 53%), diphenyl II (homocoupling product, yield
1
05%), and a small amount of benzene (yield 6%)
(Table 1, run no. 1). Here and hereinafter, the yield is
given in mol % based on the starting organometallic
compound.
3
2
reactions of Ph Bi with acids in the presence of
t-BuOOH (20 C, 24 h):
The first step of the process involves generation of
the active catalyst species Pd(0) in the course of the
3
metal interchange of PdX with the starting organo-
2
Ph Bi + 2HX + t-BuOOH
Ph BiX + t-BuOH + H O,
3 2 2
3
metallic compound, C-phenylation of ester I, and de-
composition of palladium hydride in accordance with
scheme I. Then Pd(0) enters into the redox reaction
X = O CH (85%), OAc (80%), O CEt (70%), O CBu
2
2
2
(
62%), O CCF (40%), O CPh (65%).
2
3
2
1
070-3632/05/7511-1766 2005 Pleiades Publishing, Inc.

PALLADIUM-CATALYZED C-PHENYLATION OF METHYL ACRYLATE
1767
with Ph BiX to form the phenylpalladium intermedi-
Table 1. Influence of the kind of the catalyst on the
product yields in phenylation of methyl acrylate I with the
3
2
ate PhPdX, which then either phenylates ester I to
compound II with the release of acid HX or undergoes
metal interchange with the starting organometallic
compound to form a diphenylpalladium intermediate
whose decomposition without participation of ester I
gives diphenyl [scheme (2)]:
a
system Ph Bi(O CEt) [Pd], 1 : 0.04
3
2
2
Yield, %b
Ph2
Run
no.
Catalyst
II
PhH
Ph BiX + PdX
Ph BiX + [PhPdX],
(1)
1
2
3
4
5
6
7
8
9
PdCl2
53
70
29
6
0
43
7
105
112
123
109
138
127
131
11
82
98
107
92
121
6
3
3
2
2
2
3
Pd (dba)3
2
CH =CHCO Me + [PhPdX]
2
2
Pd(OAc)2
Pd(PPh ) Cl
Traces
5
5
5
3
2
2
PhCH=CHCO Me + [HPdX],
2
PdCl + 4PPh3
2
[HPdX]
Pd(0) + HX,
PhPdX
PdCl + dppm
2
PdCl + 2dppm
4
2
Ph BiX + Pd(0)
3
2
PdCl + dppe
9
Traces
6
13
11
29
11
Ph BiX
2
2
CH =CHCO Me
PdCl + dppp
15
26
21
49
32
2
2
2
PhCH=CHCO Me + Pd(0),
2
10 PdCl + dppb
HX
Ph BiX
2
1
1
PdCl + dppf
(
2)
2
3
2
PhPdPh
Ph + Pd(0).
12 PdCl + binap
2
2
1
3
PdCl + xantphos
2
Influence of the kind of the catalyst. The results
of experiments with different salts and complexes of
Pd(0, II) as catalysts are given in Table 1. With
Pd (dba) (dba is dibenzylideneacetone), the selectivi-
a
The reactions were performed in CH CN at 50 C for 3 h in
3
the presence of air.
b
Based on Ph Bi(O CEt) .
3 2 2
2
3
ty was approximately the same as with PdCl (yield of
2
II 70%, yield of diphenyl 112%; Table 1, run no. 2).
PPh2
With Pd(OAc) , the phenylation was less efficient
2
PPh2
(yield of II 29%, yield of III 123%; Table 1, run
O
no. 3). The presence of the monodentate ligand Ph3P
in the coordination sphere of Pd drastically decreased
the yield of the target product II (to 6%), but exerted
no effect on the yield of the homocoupling product
PPh2
PPh2
binap
xantphos
(
Table 1, run no. 4). With excess Ph P (4 mol per
bered chelate ring with Pd. Such an anomalous behav-
ior of dppe is well-known [13].
3
mole of Pd), no compound II was obtained at all, and
the yield of III increased to 138%, approaching the
theoretical maximum of 150% (Table 1, run no. 5).
Thus, triphenylphosphine does not suppress the cata-
lytic homocoupling of the organobismuth compound
but suppresses the concurrent catalytic cross-coupling
with ester I [scheme (2)].
With the other diphosphines, the yield of III re-
mained high (82 127%), but the yield of II decreased.
This trend was particularly pronounced with dppf and
dppb (yield of II 21 and 26%, respectively; Table 1,
run nos. 11, 10) and less pronounced with binap and
dppm (49 and 43%, respectively; Table 1, run nos. 12,
6
). It is interesting that with a twofold excess of dppm
The effect of diphosphines is more complex. Di-
phosphines are arranged in Table 1 (run nos. 6 13) in
the order of increasing bite angle [13]. With the aim
to improve the selectivity of the process, we tested the
following ligands: dppm, bis(diphenylphosphino)-
methane, 72 ; dppe, 1,2-bis(diphenylphosphino)eth-
ane, 85 ; dppp, 1,3-bis(diphenylphosphino)propane,
the yield of II drastically decreases (to 7%), and com-
pound III becomes the prevailing reaction product
(
131%, Table 1, run no. 7). This fact can be accounted
for as follows. The four-membered chelate ring
formed by dppm with Pd is highly strained. The strain
is eliminated by the ring opening, leaving a site for
the coordination of methyl acrylate:
9
1 ; binap,
92 ; dppf, 1,1 -bis(diphenylphosphi-
96 ; dppb, 1,4-bis(diphenylphosphi-
no)ferrocene,
no)butane,
CO Me
2
99 ; and xantphos,
111 .
Ph
X
CO Me
Ph
X
P
P
2
In this series, dppe occupies a particular place: It
catalyzes neither homo- nor cross-coupling (Table 1,
run no. 8). This ligand forms a very stable five-mem-
Pd
Pd
P
P
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 11 2005

1768
MALYSHEVA et al.
Table 2. Influence of the acid residue X in the starting
reaction was performed at 50 C for 3 h in acetonini-
organometallic compound on the product yields in phenyla- trile. All the triphenylbismuth dicarboxylates entered
tion of methyl acrylate I with the system Ph BiX PdCl ,
into C-phenylation of methyl acrylate (Table 2). The
yields of II were the highest with the diformate and
dibenzoate (70 and 85%, respectively), with moderate
yields of III (46 and 75%; Table 2, run nos. 1, 6).
Approximately equal yields of II, 53 59%, were ob-
tained with triphenylbismuth dipropionate, divalerate,
and bis(trifluoroacetate) (Table 2, run nos. 3 5). The
diacetate, Ph Bi(OAc) , appeared to be the least effi-
3
2
2
a
1
: 0.04
Yield, %
Ph2
Run no.
X
II
PhH
1
2
3
4
5
6
O CH
OAc
70
26
53
57
59
85
37
31
72
46
127
105
100
55
75
86
126
51
59
3
6
18
41
54
6
2
3
2
cient: The yield of II was the lowest (26%), and the
yield of IV, the highest (127%) (Table 2, run no. 2).
Thus, under the reaction conditions, the activity of
C-phenylating agents Ph Bi(O CR) does not corre-
O CEt
2
O CBu
2
O CCF
2
3
3
2
2
O CPh
late with the strength of acids RCO H. The similar
2
2
b
7
O CPh
pattern was observed previously with Ph Sb(O CR)
2
3
2
2
c
8
O CPh
4
18
[12].
2
d
9
Cl
With the derivatives of strong acids (formic, triflu-
oroacetic, benzoic), the yields of benzene IV reach
a
The reactions were performed in CH CN at 50 C for 3 h in
3
4
1 59% and approach the yields of the cross- and
b
air. Reaction in the presence of K CO , 1 mol per mole of
2
3
homocoupling products (Table 2, run nos. 1, 5, 6).
Benzene is a secondary product of the reaction of
Bi(III) phenyl compounds with acids formed by
scheme (1):
c
organometallic compound. Reaction in the presence of Et N,
mol per mole of organometallic compound. PhCl (20%)
3
d
1
was also detected.
With a twofold excess of dppm, this vacancy is
occupied by the second dppm molecule:
Bi(III) Ph + HX
Bi(III) X + PhH.
To decrease the yield of benzene, the reaction with
triphenylbismuth dibenzoate was performed in the
presence of bases, K CO and Et N, added to neutra-
lize the acid. In these cases, indeed, the yield of ben-
zene decreased from 54 to 6 and 4%, respectively.
However, the yield of II decreased also (from 85 to
Ph
P
P
Pd
2
3
3
X
P
P
It should be noted that the yield of IV was low
0 29%) with all the palladium catalysts.
(
37 and 31%), and the yield of III increased from 75 to
Thus, PdCl and Pd (dba) are the most efficient
86 and 126% (Table 2, run nos. 7, 8). The decreased
2
2
3
catalysts for C-phenylation of I with triphenylbismuth
dicarboxylates, as well as with triphenylantimony
dicarboxylates [12]. In the subsequent experiments we
yield of methyl cinnamate in the presence of Et N
3
may be due to the fact that Et N, like Ph P, is a strong
3
3
electron-donor ligand for Pd. It occupies sites in the
palladium coordination sphere, preventing approach
of the olefin to PhPdX. In this case, the yield of Ph2
increases, similarly to the experiment with the addi-
tion of Ph P. With K CO , an exchange reaction with
used PdCl as a simpler and cheaper catalyst.
2
Solvent effect. As solvents for the reaction system
Ph Bi(O CPh) : I : PdCl = 1 : 3 : 0.04, we used,
3
2
2
2
3
2
3
along with CH CN, also CH Cl , THF, and DMF.
3
2
2
Ph Bi(O CPh) , yielding weakly reactive triphenyl-
3
2
2
The reaction was performed at 50 C for 3 h. In
bismuth carbonate, is possible:
CH Cl , THF, and DMF, the yield of II was consider-
2
2
ably lower than in CH CN: 11, 30, 32, and 85%,
respectively; the yield of III remained approximately
the same (68 77%), and the yield of benzene IV was
3
Ph Bi(O CPh) + K CO Ph BiCO + 2PhCO2K.
3
2
2
2
3
3
3
Thus, additions of bases Et N and K CO sharply
3
2
3
2
3, 18, 4, and 54%, respectively. Thus, in acetonitrile
decrease the yield of benzene but also negatively
affect the main C-phenylation process.
the extent of the reaction and the yield of II were the
highest. In this respect, compounds Ph Bi(O CR) are
3
2
2
An unexpected result was obtained in experiments
similar to Ph Sb(O CR) [12].
3
2
2
on phenylation of I with Ph BiCl . The yield of II
3
2
The influence of the acid residue X in the starting
organobismuth compound was studied with the sys-
tem Ph BiX : I : PdCl = 1 : 3 : 0.04 as example. The
was high (72%), and the yield of III was considerably
lower (51%). Also we detected benzene (18%) and
chlorobenzene (20%) (Table 2, run no. 9). Previously
3
2
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 11 2005

PALLADIUM-CATALYZED C-PHENYLATION OF METHYL ACRYLATE
1769
we found that triphenylantimony dihalides, in contrast
to carboxylates, showed no reactivity in C-phenylation
PdCl , dppm, dppe, dppp, dppb, dppf, binap, and
2
xantphos are commercially available. Methyl acrylate
was shaken with an alkali until the yellow color dis-
appeared, dried over Na SO , and distilled. All the
[12].
2
4
Thus, we found that triphenylbismuth dicarboxyl-
solvents were purified by distillation.
ates catalytically C-phenylate methyl acrylate in the
presence of Pd(0, II) compounds under mild condi-
tions; the yield of the target product is up to 85%
based on the starting organometallic compound. The
reactions involving Ph Bi(O CR) and Ph Sb(O CR)
Ph Bi(O CH) . To a solution of 2.2 g of triphenyl-
3
2
2
bismuth in 20 ml of Et O, we added 0.38 ml of for-
2
mic acid, after which we added slowly with cooling
0.53 ml of t-BuOOH. The mixture was left for 24 h
in the dark at room temperature. The crystalline pre-
cipitate thus obtained was filtered off on a glass frit,
dried, and recrystallized from methylene chloride
hexane, 1 : 4; yield 2.1 g (80%), mp 150 152 C
3
2
2
3
2
2
are characterized by similar influence of the palladium
catalyst, acid residue in the organometallic compound,
and solvent on the yield of the phenylation product.
However, there are some differences.
(
1
with decomposition) {published data [2]: mp 140
50 C (with decomposition)}.
(
1) The organobismuth compounds are more reac-
tive. The elimination of phenyl groups is complete in
h at 50 C. This is due to the lower strength of the
Bi C bond [14].
3
The other organobismuth compounds were pre-
pared similarly: triphenylbismuth diacetate, mp 187
89 C (published data [2]: 187 189 C); triphenylbis-
muth dipropionate, mp 156 C (published data [2]:
57 159 C); triphenylbismuth divalerate, mp 89 C
published data [2]: 91 C); triphenylbismuth bis(triflu-
oroacetate), mp 143 144 C (published data [2]: 143
44 C); triphenylbismuth dibenzoate, mp 166 168 C
1
(2) Being more active, compounds Ph Bi(O CR)
3 2 2
are less selective than Ph Sb(O CR) . Whereas the
3
2
2
1
(
antimony derivatives yield methyl cinnamate as a
single phenylation product, the bismuth derivatives
also yield diphenyl and benzene.
1
(3) Introduction of tertiary mono- and bidentate
(published data [2]: 167 169 C).
phosphine ligands into the coordination sphere of
palladium results in complete loss of the reactivity of
Ph Sb(O CR) [12], whereas with Ph Bi(O CR) in
most cases the cross-coupling rate only decreases to
a certain extent depending on the structure of the
phosphine and the homocoupling rate remains un-
changed. This distinction is caused by the weaker
steric demands of the homocoupling compared to
cross-coupling.
Reaction of Ph Bi(O CH) with methyl acrylate
3
2
2
and PdCl (1 : 3 : 0.04) in acetonitrile at 50 C for
2
3
2
2
3
2
2
3
0
6
h in air. A mixture of 0.265 g of Ph Bi(O CH) ,
3 2 2
.0036 g of PdCl , 0.135 ml of methyl acrylate, and
2
ml of acetonitrile was placed in a 50-ml ampule
with a silicone stopper and heated in an oven at 50 C
for 3 h. Then the liquids were distilled off under re-
duced pressure. The residue was passed through a
silica gel column using hexane ethyl acetate, 4 : 1, as
eluent. The condensate and filtrate were analyzed by
GLC for the content of volatiles.
(
4) Whereas the bismuth compounds Ph BiX are
3 2
active with both X = chloride and X = carboxylate,
the compounds Ph SbX are active only with X =
3
2
The phenylation with the other organometallic
compounds and in other solvents was performed sim-
ilarly.
carboxylate, because only the carboxy group renders
anchimeric assistance in the slow step of the metal
interchange involving Pd and Sb [12].
ACKNOWLEDGMENTS
EXPERIMENTAL
The authors are grateful to Sinor Limited Liability
Company for the submitted diphosphine ligands.
The volatile products were analyzed by GLC on
an LKhM-80 chromatograph equipped with a flame-
ionization detector; carrier gas He. Benzene was deter-
mined with a 300-cm column, stationary phase 15%
dinonyl phthalate on Chromaton N-AW-DMCS, 80 C;
methyl cinnamate and diphenyl were determined with
a 240-cm column, stationary phase 15% Apiezon L
on Chromaton N-AW-DMCS, 220 C; chlorobenzene
was determined with the same column at 130 C.
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