Hydroamination of phenylacetylene in the presence of gold-containing catalytic systems supported on carriers modified by ionic liquids

Article abstract of DOI:10.1007/s11172-015-1231-9

Ternary systems based on gold nanoparticles stabilized in ionic liquids and loaded on the supports of various nature have been prepared for the first time. The gold-containing systems obtained demonstrate activity in Markovnikov regioselective hydroamination of phenylacetylene with aniline. Catalytic properties of the gold systems synthesized depend both on the carrier structure and on the nature of the ionic liquid applied (polarity, presence of functional groups).

Full text of DOI:10.1007/s11172-015-1231-9

Russian Chemical Bulletin, International Edition, Vol. 64, No. 12, pp. 2811—2815, December, 2015
2811
Hydroamination of phenylacetylene in the presence of goldꢀcontaining catalytic
systems supported on carriers modified by ionic liquids
V. I. Isaeva,a N. I. Prokudina,a L. М. Kozlova,a L. M. Kustov,a,b L. М. Glukhov,а А. L. Tarasov,а and I. P. Beletskayab
аN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: (499) 137 2935. Eꢀmail: LMK@ioc.ac.ru, sharf@ioc.ac.ru
bChemical Department, M. V. Lomonosov State University,
Build. 3, 1 Leninskie Gory, 119992 Moscow, Russian Federation.
Ternary systems based on gold nanoparticles stabilized in ionic liquids and loaded on the
supports of various nature have been prepared for the first time. The goldꢀcontaining systems
obtained demonstrate activity in Markovnikov regioselective hydroamination of phenylacetylene
with aniline. Catalytic properties of the gold systems synthesized depend both on the carrier
structure and on the nature of the ionic liquid applied (polarity, presence of functional groups).
Key words: hydroamination, Markovnikov addition, ionic liquids, nanoparticles, catꢀ
alysis, gold.
Catalytic hydroamination is of considerable interest
for organic synthesis presenting an approach to nitrogenꢀ
containing compounds, intermediate in manufacture of
polymers, solvents, pharmaceutical drugs and surfacꢀ
tants.1,2 Despite intensive studies in this field, no effective
methods for heterogeneous catalytic hydroamination have
been developed to date. High energy barrier of the reaction
hampers the direct nucleophilic addition of amines to the
carbon—carbon multiple bond.3—6 Thermodynamically,
hydroamination of alkynes and activated alkenes is more
favourable process.7,8 To perform hydroamination, both
metalꢀbased and metalꢀfree catalytic systems have been
developed. Hydroamination reaction can be performed in
the presence of ionic liquids and acids.9—12 In certain cases
catalytic hydroamination is promoted by ionic liquid as
a medium.13
Metal nanoparticles are of interest as reactive and seꢀ
lective catalytic systems for various chemical processes
including hydroamination.14 However, in the absence of
stabilizing agents the nanoparticles form aggregates readily,
making their practical application difficult. As such
stabilizing agents oligomers may be used. For example,
poly(vinylpyrrolidone)ꢀstabilized gold nanoclusters
Au(5 at.%)/PVP) are catalysts for intramolecular hyꢀ
droamination of 2,2ꢀdiphenylꢀ4ꢀpentenylꢀ1ꢀamine and
toluenesulphoneamides.15,16 Gold nanoparticles supportꢀ
ed on chitosan biopolymer show high activity in interꢀ
molecular hydroamination of a series of alkynes with
aniline.17 Chitosan is a promising agent for stabilizing the
gold nanoparticles due to the presence of aminoꢀ and hydrꢀ
oxyl groups in each monomeric unit.
Use of ionic liquids presents a prospective approach to
nanoparticle stabilization.18 However, on carrying out the
catalytic processes, the role of an ionic liquid is not reꢀ
stricted by the stabilization of metal nanoparticles which
size is optimal for the given catalytic reaction. Cationicꢀ
anionic environment of platinum nanoparticles due to the
presence of imidazolium ionic liquid, forms a protective
layer of the ionic liquid around the metal particle and thus
inhibits the formation of active sites catalyzing the side
reactions, e.g., oligomerization of acetylene during its
hydrogenation.19
To stabilize the metal nanoparticles, functionalizaꢀ
tion of ionic liquids with chelating groups is generally
required. For example, 2,3ꢀdimethylꢀ1ꢀ[3ꢀN,Nꢀbis(2ꢀ
pyridyl)propylamido]imidazolium hexafluorophosphate,
[BMbMDPA][PF6]) ionic liquid was used to form and
stabilize palladium nanoparticles which are catalysts for
hydrogenation of substituted alkenes.20 However, someꢀ
times formation and stabilization of the transition metal
nanoparticles in imidazolium ionic liquids do not require
additional stabilizing agents.21,22 Ionic liquids can be introꢀ
duced on the surface of various carriers, and then thus
modified supports were used to immobilize the nanoꢀ
particles.
The present study is directed on the development of
novel materials based on gold nanoparticles in ionic liqꢀ
uids loaded on the supports of various nature. Ternary
systems obtained were tested as catalysts for the hydroamꢀ
ination of phenylacetylene. The special attention was foꢀ
cused on the effect of the carrier texture and of the funcꢀ
tional groups of ionic liquid modifying the carrier surface,
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2811—2815, December, 2015.
1066ꢀ5285/15/6412ꢀ2811 © 2015 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 64, No. 12, December, 2015
Isaeva et al.
NiꢀRaney were added. Hydrogenation was carried out with stirꢀ
ring until the full absorption of stoichiometric amount of hydroꢀ
gen (pressure of hydrogen 40—50 atm, 60 °С, 4—6 h). Catalysts
was filtered, methanol was removed on a rotor evaporator and
the reaction product was dried in vacuo (60—70 °С), then twice
recrystallized from isopropanol (∼100 mL). Yield 68%. 1H NMR
(D2O), δ: 1.71 (m, 4 H); 2.5—2.68 (m, 6 H); 3.52—3.64 (m, 2 H);
3.64—3.8 (m, 3 H); 3.87 (q, 1 H).
as well as on the activity of the catalytic system formed.
As supports for the ionic liquids, mesoporous silicate
MCMꢀ41 and chitosanꢀmodified silica gel were chosen.17
To stabilize gold particles on the support surface, an
available ionic liquid 1ꢀnꢀbutylꢀ3ꢀmethylimidazolium
hexafluorophosphate ([BMIM]PF6) was used. Also, a novel
ionic glucoseꢀbased glucosamine ionic liquid (resembling the
chitosan monomeric unit) — Q+Br– (1ꢀ[(2R,3S,4R,5R)ꢀ
2,3,4,5,6ꢀpentahydroxyhexyl]ꢀ1ꢀethylpyrrollidinium broꢀ
mide) has been synthesized from glucose. Glucosamine
ionic liquid was chosen to elucidate the role of functional
groups and polarity of an ionic liquid in stabilization
of nanoparticles and efficiency of the catalytic hydroꢀ
amination.
Supports loaded with ionic liquids and ternary systems
metal nanoparticles—ionic liquids—carrier) were characꢀ
terized by physicalꢀchemical methods such as lowꢀtemꢀ
perature adsorptionꢀdesorption of nitrogen, selective
chemosorption of CO, scanning electron microscopy
(SEM).
1ꢀ[(2R,3S,4R,5R)ꢀ2,3,4,5,6ꢀPentahydroxyhexyl]ꢀ1ꢀethylꢀ
pyrrolidinium bromide. To a solution of 10 g of the above amine
in 50 mL of methanol, 6 mL of ethyl bromide were added, and
heated under reflux for 4 h. Methanol was removed on a rotor
evaporator and the product was dried in vacuo until constant
weight (80 °С). Yield was quantitative. 1H NMR (D2O), δ: 1.34
(t, 3 H); 2.16 (m, 4 H); 3.40—3.90 (m, 13 H); 4.30 (m, 1 H).
Synthesis of ternary systems Au NPs@IL/Supp (NPs are
nanoparticles, IL are ionic liquids, Supp is support). Supports for
gold nanoparticles immobilizing were prepared by introducing
an ionic liquid into a solid structurized support according to the
protocols of SILP (Supported Ionic Liquid Phase) or SCILL
(Solid Catalyst with Ionic Liquid Layer), developed19,24 for carꢀ
bon nanofibers (CNF) or metal fibers (SMF). To prepare the
hydroamination catalysts, ionic liquid was loaded on a support,
then goldꢀcontaining precursor was introduced into the supportꢀ
ed ionic liquid and the resulting sample was reduced (see below).
To prepare ternary systems Au NPs@ILs/support, chitosanꢀmodꢀ
ified silica gel (КSК, large pore coarse silica gel) was also used.
Support Ch—SiO2 was prepared by a known procedure.17 Texꢀ
tural characteristics of the supports are given in Table 1.
Preꢀweighted support (0.5 g) was treated (80 °С, 5 h) with an
ionic liquid (0.1 g) dissolved in absolute methanol (1 mL), under
stirring for 0.5 h. Then the solvent was removed on a waterꢀjet
pump (80 °С, 4 h).
Goldꢀcontaining ternary systems obtained were tested
in the catalytical hydroamination of phenylacetylene with
aniline and morpholine.
Experimental
Synthesis of ionic liquids. To prepare catalytic systems, ionic
liquid [BMIM]PF6 was obtained by the known procedure.23 Ionic
liquid Q+Br– was prepared according the Scheme 1.
Goldꢀcontaining precursor was loaded on a support (1.2 g),
containing immobilized ionic liquid, from HAuCl4•4H2O (0.013 g)
solution in MeOH (2 mL) via impregnation to incipient wetness
(20 °С). Then the support containing HAuCl4•4H2O was dried
at reduced pressure (90 °С, 5 h) and evacuated using an oil
pump (1•10–3 Torr, 100 °C, 4 h).
Scheme 1
To reduce the goldꢀcontaining precursor to nanoparticles,
HAuCl4/support system was treated with sodium borohydride
(NaBH4) in MeOH (20 °С). To HAuCl4•4H2O containing supꢀ
port MeOH (3 mL) was added and then NaBH4 (0.014 g) soluꢀ
tion in MeOH (3 mL) was added slowly. The resulting mixture
was stirred for 0.5 h at 20 °С, then dried for 6 h at reduced
pressure at 90 °С. Then, the system containing gold nanopartiꢀ
cles was evacuated using an oil pump (1•10–3 Torr, 150 °C, 8 h).
Catalytic experiments. Reaction mixture containing a cataꢀ
lyst (0.1 g, 0.05—2.5% (mmol of metal)–1), phenylacetylene
Table 1. Textural characteristics of supports
Support
Specific
surface
area (BET)
/m2 g–1
Volume of
micropores
(pore diaꢀ
Volume of
mesopores
(pore diaꢀ
i. H2/NiꢀRaney , MeOH, 60 °C, 50 atm; ii. EtBr, MeOH, 65 °C.
meter ≤2 nm)
meter ≤50 nm)
1ꢀ[(2R,3S,4R,5R)ꢀ2,3,4,5,6ꢀPentahydroxyhexyl]pyrrolidine.
To a vigorously stirred mixture of 60 mL methanol and 18 mL of
pyrrolidine, 20 g of anhydrous glucose were added and heated
until complete dissolution was reached (50 °С, 20 min). Then,
the solution was placed into a stainless steel autoclave, and 5 g of
cm3 g–1
MCMꢀ41
SiO2 (КSК)
1023.9
1240.6
0.253
0.063
1.947
0.831

Hydroamination of phenylacetylene on gold
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 12, December, 2015 2813
(1 mmol), aniline or morpholine (1 mmol), toluene (1 mL),
undecane (0.07 mL, 0.3 mmol), was stirred in a glass reactor on
a magnetic stirrer in air (110 °С, 8—24 h). Composition of the
reaction solution was studied by GLC («Kristallluks» chromꢀ
atograph, equipped with flameꢀionization detector) on a capilꢀ
lary column (OVꢀ1 phase, 25 m) at a programmed heating
(100—170 °C).
Physicalꢀchemical studies of morphology and porous structure
of the samples loaded with ionic liquids. Microstructures of goldꢀ
containing catalysts obtained were studied by the scanning elecꢀ
tron microscopy (SEM) on a LEO 1455 VP instrument equipped
with an Xꢀray analyzer (Carl Zeiss). 1H NMR spectra were meaꢀ
sured on a Bruker AMꢀ300 instrument.
200 nm
Lowꢀtemperature adsorption—desorption of nitrogen. Pore
structure of materials synthesized was characterized by lowꢀtemꢀ
perature adsorption of nitrogen at –196 °С using ASAP 2020
(Micromeritics) analyzer.
Fig. 1. Micrograph of the Au(1%)/[BMIM]PF6/МСМꢀ41 sample.
Scheme 2
Selective adsorption of CO at 35 °C. CO adsorption was used
to determine specific surface area of an active phase (of metal
nanoparticles), metal dispersion and crystallite size using ASAP
2020 (Micromeritics) analyzer.
Results and Discussion
Data on adsorption and electron microscopy studies of
Au@ILs/Supp catalysts. Assuming that one CO molecule
coordinates to one metal centre, it may be deduced that
large gold nanoparticles are formed on the surface of terꢀ
nary system. For example, according to these studies for
Au(1%)/[BMIM]PF6/МСМꢀ41 system, their average diꢀ
ameter is 75 nm (Table 2).
However, selective chemosorption does not provide an
unambiguous answer to the questions of the size of gold
particles in the system. SEM method can offer additional
information on the particle size. Actually, on a microphotoꢀ
graphy of the surface of Au(1%)/[BMIM]PF6/МСМꢀ41,
gold particles of 12—15 nm size can be observed (Fig. 1).
Hydroamination of phenylacetylene. Hydroamination
of phenylacetylene with an amine (aniline, morpholine)
was chosen as a model reaction. According to the literaꢀ
ture data, the reaction proceeds as indicated in Scheme 2.
At the first step of the reaction, enamine (Markovꢀ
nikov addition product) is formed regioselectively, then
tautomerization proceeds yielding a more stable imine
((Nꢀ2ꢀbenzylidene)aniline), which hydrolyzes readily to
acetophenone under the action of traces of water present
in the system. Actually, an imine hydrolysis in aqueous acidic
medium (20 wt % of acetic acid) gives acetophenone.
The goldꢀcontaining catalysts synthesized show marked
activity in the hydroamination reactions at temperatures
>100 °С. When carrying out the catalytic reaction at
<100 °С, activity of the systems under investigation is low.
This may be due not only to kinetic effects but also to
a mass transfer limitations between the phases. Earlier,25
it has been noted that as the temperature rises, the mobilꢀ
ity of imidazolium cation increases, what in turn proꢀ
motes the mass transfer process.
In the case of low gold content in the catalyst, hydroꢀ
amination proceeds at a low rate. Under these conditions
the conversion is below 10% after 48 h. In some cases
a side reaction of phenylacetylene oligomerization cataꢀ
lyzed by a ionic liquid takes place. A dramatic increase in
the reaction rate and the product yield is observed with
catalysts containing >1 wt. % of an active metal. Optimal
conditions for attaining high conversions and therefore
high yields of the reaction products are achieved using
catalysts with a relatively high content of supported gold
(3—5%). Depending on the amine nature and the metal
content in the system, nearly quantitative conversion is
achieved after 19—30 h.
Table 2. Results for chemosorption of СО at 35 °C for the
Au(1%)/[BMIM]PF6/МСМꢀ41 system
Parameter
Value
Surface area of the metal particle/m2 g–1
Sample
Metal
Catalytic activity, conversion of phenylacetylene and
the yield of the reaction products depend significantly on
the nature of the support and ionic liquid. With catalysts
prepared by loading [BMIM]BF4 onto a mesoporous siliꢀ
ca support, Au(1%)/[BMIM]BF4/MCMꢀ41, conversion
reaches 97% for 19—20 h (Table 3). However, in the presꢀ
3.5•10–2
3.5
Proportion of metal atoms
on the catalyst surface (%)
Crystallite size/nm
1.3
75

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Russ.Chem.Bull., Int.Ed., Vol. 64, No. 12, December, 2015
Isaeva et al.
ence of Au(1%)/QBr/MCMꢀ41 catalyst containing a novel
glucosamine ionic liquid carried by the same support, the
rate of hydroamination of phenylacetylene decreases (see
Table 3). A further decrease in the reaction rate of the
hydroamination process in the presence of the said cataꢀ
lyst is observed when an aromatic amine (aniline) is reꢀ
placed by an aliphatic one (morpholine). In this case conꢀ
version is 34% after 25 h, nevertheless the reaction proꢀ
ceeds selectively.
lytic mixture was 89.5 wt.% at 96% conversion, while the
yield of acetophenone was as low as 6.5 wt.%. In the case
of Au(1%)/[BMIM]BF4/MCMꢀ41 catalyst at the same
conversion the content of acetophenone in the products
reaches 31.1 wt.% due to the imine hydrolysis. Such
a difference in selectivity towards imine may be mainly due
to the fact that the effect of active acid sites of the ionic
liquid responsible for the imine hydrolysis is minimized
with an increasing gold content on the support.
Increase in the hydroamination rate in the presence of
Au(1%)/[BMIM]BF4/MCMꢀ41 catalytic system (see
Table 3) may be the result of using МСМꢀ41 mesoporous
silica with a high specific surface area as a solid support.
The same effect was observed when NꢀBETA zeolite26
was used as a support for the phase active in this reaction
(vide supra). The catalyst comprising gold nanoparticles
immobilized using a novel ionic liquid QBr, Au(5%)/QBr/
ChꢀSiO2) (Ch is chitosan), shows somewhat decreased
activity compared to the Au(1%)/[BMIM]BF4/MCMꢀ41
system/ We can take ТОF as a measure of catalytic activꢀ
ity. TOF is the turnover frequency, i.e. the frequency of
cycles, i.e. the number of conversions of substrates moles
per mole of the surface atoms per 1 h. We found that
Differences in activity of the ternary systems outlined
above may be associated with the features of formation
and distribution of the ionic liquid layer on the surface of
various supports. On the one hand, specificity of the naꢀ
ture of any given ionic liquid and features of its layer results
in differences in solubility and diffusion of reagents and
reaction products. On the other hand, supported ionic
liquids differ in functional groups facilitating stabilization
of gold particles of various size on the support surface. As
mentioned above, the highest reaction rate was achieved
with Au(1%)/[BMIM]BF4/MCMꢀ41. This is probably reꢀ
lated both to the stabilization of the sizeꢀdefined gold parꢀ
ticles on this texturized mesoporous support due to the
ionic liquid and with the distribution of the latter on the
support, its polarity and viscosity providing the mass transꢀ
fer. Earlier27 it was noted that the catalytic system based
on more polar ionic liquid is characterized by higher activity.
The reaction rate also depends on the amine nature.
Thus, addition of an aromatic amine (aniline) proceeds at
higher rate compared to that observed in the presence of
an aliphatic amine such as morpholine (see Table 3).
Auꢀcontaining catalytic systems show high stability.
No "washingꢀoff" of the gold nanoparticles into the reacꢀ
tion solution is observed during the reaction. The catalyst
retains its activity during three catalytic cycles. Further
achievements in development of hydroamination catalysts
may be sought in the use of hybride nanomaterials.26
Thus, novel ternary systems based on gold nanoꢀ
particles in ionic liquids loaded on various supports
a TOF value for the chitosan based catalyst is 7.6•103 h–1
whereas that for the MCMꢀ41 based system is 8.5•103 h–1
,
.
High conversion of phenylacetylene (96—97%) in the presꢀ
ence of these catalysts is achieved practically at the same
reaction time (19—20 h). The value of conversion obꢀ
tained for the above ternary catalytic systems suggests that
these systems are more active than the best known heteroꢀ
geneous catalysts based on gold nanoparticles. For example,
on carrying out hydroamination of phenylacetylene with
aniline in the presence of Au—C hybride materials (С are
various carbon supports including singleꢀ and multiꢀwall
nanotubes), it was found that conversion doesn´t exceed
∼79.5% after 24 h.25
When the reaction on the Au(5%)/QBr/ChꢀSiO2 catꢀ
alyst was completed, the content of an imine in the cataꢀ
Table 3. Results for hydroamination of phenylacetylene with aniline in the presence of Auꢀcontaining catalystsa
Catalystb
TOF/h–1
Reaction time
/h
Conversion
Yield of imine
Yield of
acetophenone
%
Au(0.1%)/[BMIM]PF6/МСМꢀ41
Au(5%)/Q/Ch—SiO2
Au(1%)/Q/MCMꢀ41
Au(1%)/Q/MCMꢀ41с
Au(1%)/[BMIM]BF4/MCMꢀ41
Au(1%)/[BMIM]BF4/MCMꢀ41d
5.8•102
7.6•103
6.1•103
2.5•102
8.5•103
9.5•103
24
19
30
25
20
20
17.0
96.0
88.5
34.0
97.0
96.2
15.6
89.1
44.8
12.2
65.9
63.6
10.4
16.5
43.4
21.8
31.1
32.4
a Catalyst, 0.1 g (0.05—2.5% (mmol of metal)–1), phenylacetylene (1 mmol), aniline (1 mmol), Т = 110 °С.
b Q is glucosamine ionic liquid.
c Hydroamination reaction between phenylacetylene and morpholine.
d Reaction in the presence of styrene.

Hydroamination of phenylacetylene on gold
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 12, December, 2015 2815
13. J. J. Brunet, N.C. Chu, O. Diallo, Organometallics, 2005,
24, 3104.
14. V. I. Parvulescu, C. Hardacre, Chem. Rev., 2007, 107, 2615.
15. H. Kitahara, H. Sakurai, Chem. Lett., 2010, 39, 46.
16. H. Kitahara, H. Sakurai, J. Organometal. Chem., 2011,
696, 442.
17. A. Corma, P. Concepciуn, I. Domнnguez, V. Fornés, M. J.
Sabater, J. Catal., 2007, 251, 39.
18. C. W. Scheeren, G. Machado, S. R. Teixeira, J. Morais,
J. B. Domingos, J. Dupont, J. Phys. Chem. B, 2006, 110, 13011.
19. M. Ruta, G. Laurenczy, P. J. Dyson, L. KiwiꢀMinsker,
J. Phys. Chem. C, 2008, 112, 17814.
(Au NPs@IL/Supp) have been prepared for the first time.
Novel glucoseꢀbased ionic liquid capable of stabilizing
gold particles was synthesized. To attain high conversion
of phenylacetylene in the hydroamination reaction with
the above ionic liquid layer—solid support systems it is
important to have gold nanoparticles with the size around
12—15 nm. Such relatively large particles are formed when
the content of metal in the sample is ≥1 wt.%.
The work was financially supported by the Russian
Science Foundation (Project No. 14ꢀ50ꢀ00126).
20. Y. Hua, H. Yang, Y. Zhang, Z. Hou, X. Wang, Y. Qiao,
H. Li, B. Feng, Q. Huang, Catal. Commun., 2009, 10, 1903.
21. J. Dupont, G. S. Fonseca, A. P. Umpierre, P. F. P. Fichtꢀ
ner, S. R. Teixeira, J. Am. Chem. Soc., 2002, 124, 4228.
22. G. S. Fonseca, A. P. Umpierre, P. F. P. Fichtner, S. R.
Teixeira, J. Dupont, Chem. Eur. J., 2003, 9, 3263.
23. J. G. Huddleston, A. E. Visser, W. M. Reichert, H. D. Wilꢀ
lauer, G. A. Broker, R. D. Rogers, Green Chem., 2001, 3, 156.
24. M. Ruta, I. Yuranov, P. J. Dyson, G. Laurenczy, L. Kiwiꢀ
Minsker, J. Catal., 2007, 247, 269.
25. A. SeralꢀAscaso, A. Luquin, M. J. Lázaro, G. F. de la Fuꢀ
ente, M. Laguna, E. Muсoz, Appl. Catal. A: Gen., 2013,
456, 88.
26. V. P. Ananikov, E. A. Khokhlova, M. P. Egorov, A. M.
Sakharov, S. G. Zlotin, A. V. Kucherov, L. M. Kustov, M. L.
Gening, N. E. Nifantiev, Mendeleev Commun., 2015, 25, 75.
27. C. Sievers, O. Jimenez, R. Knapp, X. Li, T. E. Mueller,
A. Tuerler, B. Wierczinski, J. A. Lercher, J. Mol. Catal. A:
Chem., 2008, 279, 187.
References
1. T. G. Müller, M. Beller, Chem. Rev., 1998, 98, 675.
2. M. Beller, A. Tillack, J. Seayad, Transition Metals for
Organic Synthesis, vol. 2, 2nd ed., WileyꢀVCH, Weinheim,
2004, 403 pp.
3. F. Pohlki, S. Doye, Chem. Soc. Rev., 2003, 32, 104.
4. Y. Shi, T. Ciszewski, A. L. Odom, Organometallics, 2001,
20, 3967.
5. Y. Li, T. J. Marks, Organometallics, 1996, 15, 3770.
6. P. J. Walsh, A. M. Baranger, R. G. Bergman, J. Am. Chem.
Soc., 114.
7. D. Steinborn, R. Taube, Z. Chem., 1986, 26, 349.
8. M. Beller, J. Seayad, A. Tillack, H. Jiao, Angew. Chem.,
2004, 43, 3368.
9. J. Zhang, C.ꢀG. Yang, C. He, J. Am. Chem. Soc., 2006,
128, 1798.
10. H. Kitahara, I. Kamiya, H. Sakurai, Chem. Lett., 2009,
38, 908.
11. K. Marcsekova, S. Doye, Synthesis, 2007, 1, 145.
12. L. Yang, L.ꢀW. Xu, C.ꢀG. Xia, Synthesis, 2009, 12, 1969.
Received September 8, 2015;
in revised form November 5, 2015