Palladium-catalyzed reaction of some triphenylbismuth(V) sulfonates and phenolates with methyl acrylate

Article abstract of DOI:10.1134/S1070363206080135

Triphenylbismuth(V) derivatives Ph₃BiX₂ [X = OC ₆H₂(NO₂)₃-2,4,6, OC ₆H₂(NO₂-4)Br₂-2,6, OTs, OSO ₂C₆H₄OH-4] react with methyl acrylate and PdCl₂ (1:3:0.04 molar ratio) in acetonitrile at 20°C to form the cross-coupling products, methyl cinnamate (0.26-0.51 mol mol^-1 starting bismuth compound) and methyl hydrocinnamate (0-0.17 mol mol ^-1); diphenyl, the homocoupling product (0-0.13 mol mol ^-1); and benzene (0.02-0.15 mol mol^-1). The reaction of Ph₃Bi(OSO₂C₆H₄OH-4)₂ is characterized by the selective formation of methyl cinnamate, but the reagent activity is low. Ph₃Bi(OTs)₂ exhibits the highest activity among the derivatives studied, but the reaction selectivity is low. The mechanisms of the palladium-catalyzed formation of homo-and cross-coupling products are proposed. Nauka/Interperiodica 2006.

Full text of DOI:10.1134/S1070363206080135

ISSN 1070-3632, Russian Journal of General Chemistry, 2006, Vol. 76, No. 8, pp. 1249 1252.
Pleiades Publishing, Inc., 2006.
Original Russian Text A.V. Gushchin, Yu.B. Malysheva, D.Yu. Kosov, V.V. Sharutin, 2006, published in Zhurnal Obshchei Khimii, 2006, Vol. 76, No. 8,
pp. 1301 1304.
Palladium-Catalyzed Reaction of Some Triphenylbismuth(V)
Sulfonates and Phenolates with Methyl Acrylate
a
a
a
b
A. V. Gushchin , Yu. B. Malysheva , D. Yu. Kosov , and V. V. Sharutin
a
Lobachevsky Nizhni Novgorod State University,
pr. Gagarina 23, Nizhni Novgorod, 603950 Russia
e-mail: gushchin@mail.nnov.ru
b
Blagoveshchensk State Pedagogical University, Blagoveshchensk, Russia
Received September 2, 2005
Abstract Triphenylbismuth(V) derivatives Ph BiX2 [X = OC H (NO ) -2,4,6, OC H (NO -4)Br -2,6,
3
6
2
2 3
6
2
2
2
OTs, OSO C H OH-4] react with methyl acrylate and PdCl (1: 3: 0.04 molar ratio) in acetonitrile at 20 C to
2
6
4
2
1
form the cross-coupling products, methyl cinnamate (0.26 0.51 mol mol starting bismuth compound) and
methyl hydrocinnamate (0 0.17 mol mol ); diphenyl, the homocoupling product (0 0.13 mol mol ); and
benzene (0.02 0.15 mol mol ). The reaction of Ph Bi(OSO C H OH-4) is characterized by the selective
1
1
1
3
2
6
4
2
formation of methyl cinnamate, but the reagent activity is low. Ph Bi(OTs) exhibits the highest activity
3
2
among the derivatives studied, but the reaction selectivity is low. The mechanisms of the palladium-catalyzed
formation of homo- and cross-coupling products are proposed.
DOI: 10.1134/S1070363206080135
Organometallic bismuth derivatives can be used as
mild reagents for C-phenylation of unsaturated com-
reactions of triphenylbismuth(V) dicarboxylates,
thoroughly studied previously [8, 10].
pounds. Ph Bi was first used for C-phenylation of
3
In the reaction of triphenylbismuth picrate with I
styrene in the presence of stoichiometric amounts of
palladium [1]. The same system was later used for the
phenylation of 1-octene, ethyl acrylate [2], and methyl
acrylate [3]. C-Phenylation in the presence of catalytic
amounts of palladium was carried out with bismutho-
nium salts [4] and diphenylbismuth chloride [5]. In
all the coupling reactions, diphenyl formed in signif-
icant amounts as by-product. The homocoupling of
organobismuth(III,V) compounds to diaryls in the
presence of palladium salts was specially studied in
in the presence of PdCl (see table), the main cross-
2
coupling product was methyl cinnamate (yield
.40 mol mol 1 starting Ph BiX ). Also we isolated
3 2
0
the second cross-coupling product, methyl hydro-
1
cinnamate III (yield 0.02 mol mol ), the homocoupl-
1
ing product, diphenyl IV (yield 0.13 mol mol ), and
1
benzene V (yield 0.09 mol mol ). The total consump-
tion of phenyl groups (this value characterizes the
extent of the reaction) was 0.77 mol mol 1 (see table,
run no. 1).
[
6, 7].
Triphenylbismuth dicarboxylates were studied as
Ph BiX + CH =CHCO Me
3
2
2
2
mild reagents for C-phenylation of methyl acrylate I
at 20 50 C. The reaction gave methyl cinnamate,
diphenyl, and benzene. The yields of these products
and their ratio significantly depend on the structure of
the acid residue [8 10].
I
0
.04 mol PdCl , 20 C, 24 h
2
PhCH=CHCO Me
2
CH CN
3
II
+
PhCH CH CO Me + Ph + PhH,
2 2 2 2
III
IV
V
In this study we examined the phenylating power
of a series of triphenylbismuth phenolates and sul-
X = OC H (NO ) -2,4,6, OC H (NO -4)Br -2,6, OTs,
6
2
2 3
6
2
2
2
fonates in a model reaction with ester I. Ph Bi[OC H
3
6
2
OSO C H OH-4.
2 6 4
(
NO ) -2,4,6] ,
Ph Bi[OC H (NO -4)Br -2,6] ,
2
3
2
3 6 2 2 2 2
Ph Bi(OTs) , and Ph Bi(OSO C H OH-4) were used
as starting organometallic compounds. The typical
Replacement of two nitro groups in thiphenylbis-
muth picrate by less electron-withdrawing bromine
atoms led to a certain decrease in the total activity of
the organometallic compound (total Ph group con-
3
2
3
2
6
4
2
reaction conditions (Ph BiX :I:PdCl ratio 1:3:0.04,
3
2
2
acetonitrile, 20 C, 24 h) were similar to those of the
1249

1250
GUSHCHIN et al.
Effect of the organobismuth compound structure on the yields of the products of methyl acrylate phenylation with the
a
Ph BiX PdCl (1: 0.04) system
3
2
2
Yield, mol mol 1 Ph BiX2
3
Exp. no.
Organobismuth compound
Ph Bi[OC H (NO ) -2,4,6]
II
III
IV
V
Phb
1
2
3
4
0.40
0.36
0.51
0.26
0.02
0.02
0.17
0
0.13
0.07
0.12
0
0.09
0.02
0.15
0.05
0.77
0.52
1.07
0.31
3
6
2
2 3
2
Ph Bi[OC H (NO -4)Br -2,6]
3
6
2
2
2
2
Ph Bi(OSO C H Me- )
3
2
6
4
4 2
Ph Bi(OSO C H OH- )
3
2
6
4
4 2
a
b
The reactions were carried out in CH CN at 20 C for 24 h in air.
3
( Ph) Total consumption of phenyl groups.
Ph BiX + PdX Ph BiX + PhPdX,
1
sumption was 0.52 mol mol ), mainly at the expense
(1)
3
2
2
2
3
of decreased yield of IV and V (see table, run no. 2).
PhPdX + CH =CHCO Me
2
2
Triphenylbismuth tosylate showed the highest ac-
tivity. The 1 phenyl group consumption was
PhCH=CHCO Me + HX + Pd(0),
(2)
(3)
2
Ph BiX + Pd(0)
PhPdX + Ph BiX,
2
1
.07 mol mol . As compared to phenolates, the yields
3
2
1
of target product II (0.51 mol mol ), compound III
Ph BiX + CH =CHCO Me
1
1
3
2
2
2
(
0.17 mol mol ), and benzene V (0.15 mol mol )
PdX2
increased (see table, run no 3). C-Phenylation of I
PhCH=CHCO Me + Ph BiX + HX,
(4)
2
2
remained the major reaction pathway.
X = OC H (NO ) -2,4,6, OC H (NO -4)Br -2,6, OTs,
6
2
2 3
6
2
2
2
Replacement of the methyl group in the phenyl
residue by a stronger electron-donor substituent,
hydroxy group, leads to a twofold decrease in the
OSO C H OH-4.
2
6 4
The activity of triphenylbismuth sulfonates and
phenolates used in this study for C-phenylation of
ester I is similar to that of the previously studied
triphenylbismuth carboxylates and halides. The yields
1
yield of II (to 0.26 mol mol ) and to a strong de-
1
crease in the yield of V (to 0.05 mol mol ). Diphenyl
and methyl hydrocinnamate were not detected at all
1
(
see table, run no 4). Thus, the latter system appeared
of II with these reagents were 0.20 0.90 mol mol
to be most selective with respect to methyl acrylate
phenylation, but the total consumption of phenyl
[
8, 9].
1
Formation of diaryls in the reactions of organobis-
groups was as low as 0.31 mol mol .
muth compounds with palladium salts has been
thoroughly studied [6, 7]. It proceeds via formation
and reductive decomposition of the diarylpalladium
intermediate. We have shown that the transfer of two
phenyl groups from bismuth to palladium occurs not
simultaneously but in two consecutive steps [9].
Thus, ester II is the main C-phenylation product
of acrylate with triphenylbismuth(V). Its yield reaches
1
0
.51 mol mol .
We believe that product II is formed by a chain of
transformations involving Pd(0) Pd(II) cyclic trans-
formations, as it was established for Bi(V) dicarboxy-
lates [9]. In the first step of the process the starting
organometallic compound undergoes transmetallation
with the formation of active phenylpalladium inter-
mediate PhPdX [Eq. (1)]. The latter is known [11] to
act as a C-phenylation agent of ester I with the ex-
clusive formation of the energetically more favorable
trans isomer of II [Eq. (2)]. In the process, palladium
is reduced to a Pd(0) complex stabilized in solution
with such electron-donating ligands as acetonitrile and
organometallic and unsaturated compounds. Then, in
the redox transmetallation with Ph BiX , the Pd(0)
We believe that the PhPdX intermediate formed by
Eq. (2) reacts with tri- and pentavalent bismuth phenyl
derivatives to form unstable Ph Pd giving Ph and
2
2
Pd(0) [Eqs. (5), (6)]. The latter returns into the cata-
lytic cycle by reaction (3).
PhPdX + Ph [Bi(III, V)]
Ph Pd + BiX + [Bi(III, V)] X,
(5)
(6)
2
3
Ph Pd
Ph + Pd(0).
2
2
It is important that, in the reactions with triphenyl-
bismuth sulfonate and phenolate, the yields of II in
all cases were 3 6 times higher than the yields of IV
(see table). This feature distinguishes the organo-
metallic compounds in question from triphenylbis-
3
2
complex is converted back to PhPdX [Eq. (3)]. Partial
symmetrization of Ph BiX gives Ph Bi which was
2
3
found among the reaction products. The overall
C-phenylation process of I is described by Eq. (4).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 8 2006

PALLADIUM-CATALYZED REACTION OF SOME TRIPHENYLBISMUTH(V) SULFONATES
1251
muth carboxylates and halides, for which the ratio of
II and IV was in the range 0.32 1.4 [8, 9].
but under harsh conditions (180 C) [12]. Recently we
examined the Ph SbCl + PdCl system (1:0.04) in
4
2
hydrophenylation of ester I at 50 C and discussed the
The table shows that, along with II and IV, the
hydrophenylation product III is formed in most cases.
With the most active triphenylbismuth tosylate, its
possible reaction pathways. The yield of III reached
1
0
.32 mol mol organometallic compound [13, 14].
1
yield reaches 0.17 mol mol . The hydrophenylation
Here we suggest that the scheme of methyl acrylate
involves simultaneous hydrogenation and phenylation
of the substrate unsaturated group and is therefore of
special interest for organic synthesis. Up to now, only
hydrophenylation of , -unsaturated aldehydes and
ketones with a complex system consisting of an organ-
oantimony compound, AgOAc, and Pd(OAc)2 in
hydrophenylation with triphenylbismuth tosylate and
phenolate is similar to that presented in [13, 14]. The
intermediate PhPdX formed by reaction (2) enters the
1,4-addition with I [Eq. (7)]. The HX released in the
course of phenylation of I according to Eq. (2) causes
the acidolysis of palladium alkoxide [Eq. (8)]. The
released ketene hemiacetal undergoes proton transfer,
transforming into stable product III [Eq. (9)].
1
:1:0.04 ratio was carried out under mild conditions
at 20 C [11]. A simple system based on benzene and
Ir(acac)2 effects hydrophenylation of any alkenes,
O
OPdX
PhPdX + CH =CH C
PhCH C=C
,
2
2
(
7)
OMe
OMe
OPdX
OH
HX + PhCH CH=C
PdX + PhCH CH=C
,
(8)
(9)
2
2
2
OMe
OMe
OH
O
PhCH2 CH=C
.
PhCH CH=C
2
OMe
OMe
Thus, methyl hydrocinnamate III is formed in
parallel to the phenylation product II. We never ob-
served formation of III without formation of II (see
table).
bismuth carboxylates. Also, the hydrophenylation
product III, absent in the case of bismuth carboxylates,
was detected.
EXPERIMENTAL
Benzene V is the secondary product of the reaction
of bismuth(II) phenyl derivatives with the acids re-
leased in the phenylation reactions [Eq. (2)].
Volatile reaction products was analyzed by GLC
on a Tsvet-580 chromatograph equipped by flame
ionization detector. Argon was used as a carrier gas.
For methyl hydrocinnamate, methyl cinnamate, and
diphenyl, we used a 2000 3-mm column, stationary
phase 15% Apiezon L on Chromaton N-AW-DMCS,
column temperature 230 C. Benzene was determined
on the same column at 130 C.
HX + Ph BiX
2PhH + BiX3.
2
It is known that the rate of this reaction strongly
depends on temperature and on the strength of the HX
acid [15]. In this connection, it should be noted that,
under the conditions studied (CH CN, 20 C, 24 h),
3
1
Reaction of Ph3Bi[OC6H2(NO2)3-2,4,6]2 with
the yields of benzene were low (0.02 0.15 mol mol )
methyl acrylate and PdCl (1:3:0.04). A mixture
2
and did not differ strongly. This result was explained
by the approximately equal strength of acids released
in the course of phenylation and the leveling effect of
acetonitrile exhibiting weak base properties [16].
of 0.448 g of Ph Bi[OC H (NO ) -2,4,6] , 0.0036 g
3
6
2
3 3
2
of PdCl , 0.135 ml of methyl acrylate, and 6 ml of
2
acetonitrile was left for 24 h at room temperature in
air. Then the mixture was evaporated at reduced
pressure. The residue was passed through a silica gel
column, elution with 4:1 hexane ethyl acetate. The
content of volatile products in the condensate and
filtrate was determined by GLC. Phenylation with the
other organometallic compounds was carried out
similarly.
Thus, we found that triphenylbismuth phenolates
and tosylates, similarly to the previously studied
carboxylates, readily enter the PdCl -catalyzed reac-
2
tion with unsaturated substrate I at room temperature
to form simultaneously products II, IV, and V, but
the yield of IV is several times lower compared to
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1252
GUSHCHIN et al.
vol. 75, no. 11, p. 1849.
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