Polyaromatic Products of Three-Component Coupling of Aryl Halide with Two Molecules of Arylacetylene and Arylboronic Acid under Ligand-Free Catalysis Conditions

Article abstract of DOI:10.1134/S1070428019050154

The aryl halide-arylacetylene-arylboronic acid three-component coupling in the presence of a Pd catalyst containing no organic ligands is described. The reaction routes that take place in the reaction system are shown to include the consecutive carbopalla

Full text of DOI:10.1134/S1070428019050154

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2019, Vol. 55, No. 5, pp. 678–681. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Zhurnal Organicheskoi Khimii, 2019, Vol. 55, No. 5, pp. 782–786.
Polyaromatic Products of Three-Component Coupling of Aryl
Halide with Two Molecules of Arylacetylene and Arylboronic
Acid under Ligand-Free Catalysis Conditions
E. V. Yarosha, E. V. Larinaa, N. A. Lagodaa, A. A. Kurokhtinaa, and A. F. Schmidta,*
a Irkutsk State University, ul. K. Marksa 1, Irkutsk, 664003 Russia
*e-mail: aschmidt@chem.isu.ru
Received December 13, 2018; revised February 10, 2019; accepted February 21, 2019
Abstract—The aryl halide–arylacetylene–arylboronic acid three-component coupling in the presence of a Pd
catalyst containing no organic ligands is described. The reaction routes that take place in the reaction system
are shown to include the consecutive carbopalladation of two arylacetylene molecules, leading to unsaturated
polyaromatic compounds. The possibility of controlling the alternative reaction routes is demonstrated.
Keywords: three-component coupling, polyaromatic compounds, catalysis, palladium, carbopalladation
DOI: 10.1134/S1070428019050154
The natural result of many years of research into
traditional two-component coupling reactions of aryl
halides with various nucleophiles [1] was that the
regularities established for these processes were
extended to more intricate related processes. Thus, in
2003, Zhou et al. demonstrated for the first time a
three-component aryl halide–alkyne–arylboronic acid
coupling reaction leading to tetrasubstituted alkenes [2, 3].
or several consecutive acetylene carbopalladation
stages and in the presence of an additional nucleophile,
i.e. under three-component coupling conditions. The
additional nucleophile (organometallic reagent [2],
arylboronic acid [2, 5], alkene [6, 7], or terminal
alkyne [8, 9]) can intercept intermediates that build-up
their structure in consecutive carbopalladation stages,
which makes it possible to obtain linear acyclic
products by interrupting the sequence of
carbopalladation stages with regeneration of the initial
form of the catalyst [Pd(0) compound].
Previously we found that two-component aryl
halide–arylacetylene coupling under ligand-free
catalysis conditions [4] and in the absence of Cu(I)
compounds (copper-free variant of the Sonogashira
reaction [1]) involves carbopalladation of the acetylene
molecule by the σ-aryl palladium complexes formed
from aryl halide and zero-valent palladium, which
occurs in preference to the traditional Sonogashira
reaction. Therewith, two or even three consecutive
carbopalladations may take place: carbopalladation of
arylacetylene with an σ-aryl palladium complex to
form the corresponding σ-alkenyl palladium complex
which can further effect carbopalladation of two more
arylacetylene molecules. This reaction sequence was
completed by intramolecular cyclization to form
tetraarylbenzenes and tetraarylfulvenes.
We found that using the simplest ligand-free
catalytic system based on palladium acetate and
sodium acetate as a base (without phosphorus and
nitrogen-containing ligands, Scheme 1) with iodo-
benzene, tolane, and phenylboronic acid the reaction,
along with the products of two-component coupling of
aryl halide and alkyne [triphenylethylene (1)], gave the
products of three-molecular assembly of two
components [tetraphenylnaphthalene (3), pentaphenyl-
butadiene (4)] and three components [tetraphenyl-
ethylene (2)], as well as of four-molecular assembly of
all the three components [hexaphenylbutadiene (5)].
Analysis of the mass spectra of the products
obtained by varying the para-substituents in the
benzene ring of aryl halide and arylboronic acid
provides clear evidence for the incorporation of one
The obtained evidence for carbopalladation
involving more than one arylacetylene molecule
allowed us to suggest that this process occurs via one
678

POLYAROMATIC PRODUCTS OF THREE-COMPONENT COUPLING OF ARYL HALIDE
679
Scheme 1.
I
Ph
Ph
Ph
H
Ph
Ph
Ph
Ph
Ph
2
Ph
2
R
+
Ph
Ph
R
Pd(0)
Ph
2
)
R
H
Ph
O
Ph
(
3, 12_70%
3a: R = H;
B
r
4, 2_12%
Ph
A
4a: R = H;
3b: R = OCH3.
Ph
4b: R = OCH3.
Ph
Ph
Ph
Ar
Ph
Ph
Ph
Ph
Ar
Ph
H
Ph
Ph
R
R
2, 5_57%
2a: R = H, Ar = Ph;
2b: R = OCH3, Ar = Ph;
2c: R = H, Ar = 4-CH3C6H4.
5, 4_20%
R
5a: R = H, Ar = Ph;
5b: R = OCH3, Ar = Ph;
5c: R = H, Ar = 4-CH3C6H4.
1, 1_21%
1a: R = H;
1b: R = OCH3.
aryl fragment of the aryl halide molecule in all
products 1–5, as well as the incorporation of one aryl
fragment of the arylboronic acid in products 2 and 5.
These results rule out the oxidative variant of the
reaction involving only arylboronic acid and acetylene
and give unambiguous evidence showing that
compounds 2 and 5 are formed by three-component
coupling. The composition of the products suggests the
following routes of their formation in the studied three-
component coupling reaction (Scheme 2).
reaction). Products 3–5 arise from transformations of
σ-alkenyl palladium complex C formed by consecutive
carbopalladation of two tolane molecules. The
formation of tetraphenylnaphthalene 3 occurs as a
result of the completion of the catalytic cycle via
intramolecular C–H activation in complex C with
closure of a new six-membered ring (similar to
so-called direct arylation of aromatic compounds [10]).
Pentaarylbutadiene 4 is formed by an alternative
route of completion of the catalytic cycle, involving
reduction of σ-alkenyl palladium complex C,
which is accompanied by regeneration of the starting
Pd(0) compound too, whereas hexaarylbuta-
diene 5 arises from reduction of complex С with the
third component, viz. arylboronic acid via the Suzuki–
Miyaura reduction.
Triarylethylene 1 is formed by the reduction of σ-
alkenyl palladium complex B, a product of the carbo-
paladation of tolane with palladium–aryl halide adduct
ArPdX A. Tetraarylethylene 2 is formed by the
reaction of the same complex B with arylboronic acid
(transmetalation similar to the Suzuki–Miyaura
Scheme 2.
[H]
ArX
Pd(0)
1
Pd(0)
Pd(0)
reduction
Ph
Ar
PdX
Ph
Ph
Ph
Ar'B(OH)2
transmetalation
ArPdX
2
carbopaladation
A
3
4
5
Pd(0)
Pd(0)
Ph
Ph
C-H-activation
Ph
Ph
B
PdX
Ph
[H]
carbopaladation
Ar
reduction
Ph
Ar'B(OH)2
C
Pd(0)
transmetalation
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 5 2019

YAROSH et al.
680
Despite the fact that polyaromatic unsaturated
ligand-free catalytic systems in an available organic
solvent holds promise as a synthetic approach to
different types of unsaturated polyaromatic products
via consecutive carbopalladation of two arylacetylene
molecules. Preliminary results indicate the possibility
of controlling the selectivity of the process in order to
optimize the yield of one or another product.
products of coupling with two alkyne molecules, like
3–5, are of great interest for the production of modern
optoelectronic and emission materials [11], a limited
number of works have been published, where their
formation in two- and three-component coupling
reactions was detected. The first detection of
compound 3 among Pd-catalyzed reaction products
was reported by Wu et al. [12] more than 20 years ago,
but the authors used a phosphine-containing catalytic
system.
EXPERIMENTAL
Gas chromatography–mass spectrometry was
performed on a Shimadzu QP 2010 Ultra instrument
(column 30 m × 0.25 mm × 0.25 µm GsBP-5MS),
carrier gas He, programmed temperature from 100 to
250°С, m/z range 15–900, scan rate 5000 amu/s. The
measured mass spectra were compared with those
retrieved from libraries (Wiley, NIST, NIST05) and
obtained for authentic samples (Aldrich).
Under the conditions of the most practically
attractive ligand-free catalysis, tetraphenylnaphthalene
3 was obtained only as a by-product in an aryl halide–
alkyne–alkene three-component system in the presence
of silver acetate as a base [13]. Wu et al. [14] reported
the formation of tetraarylnaphthalenes via consecutive
carbopalladation of two arylacetylene molecules
during two-component oxidative coupling of alkyne
with arenes, but the reaction required the use of
stoichiometric oxidant amounts and was quite time-
consuming (up to 36 h).
Three-component coupling in the aryl halide–
tolane–arylboronic acid system. The reaction was
accomplished in a thermostated reactor (80–140°С)
equipped with a rubber membrane and a magnetic
stirrer (stirring speed 477.5 rpm), mixing in DMF or a
4 : 1 DMF–water mixture (5 mL) aryl iodide, tolane,
and arylboronic acid (5 mmol each), PdCl2 (0.0016–
0.08 mmol), NaOAc (6.5 mmol) as a base, and
naphthalene (1 mmol) as an internal standard. In the
cases, when sodium formate or oxygen was used, their
amounts were 0.975 and 0.8 mmol, respectively. The
samples periodically withdrawn from the reaction
mixture were analyzed by GC–MS; the product yields
were determined by the internal standard method using
authentic sample calibration.
As only known precedent of the targeted synthesis
of tetraarylnaphthalenes 3 by the ligand-free route
described in this paper we can mention the work of Bej
et al. [15], but the authors used such a specific solvent
as polyethylene glycol. The formation of type 5
products in ligand-free conditions by carbopalation of
two arylacetylene molecules was observed in two-
component aryl acetylene—arylboronic acid oxidative
coupling [16], but here equimolar oxidant amounts
(silver salts) were required too to regenerate Pd(II)
complexes that reacted with arylboronic acid at the
stage of formation of σ-aryl palladium complexes. As
far as we know, the formation of type 4 products under
catalytic conditions has never been reported.
1,1,2-Triphenylethene (1а). Mass spectrum, m/z
(Irel, %): 256 (100.0) [M]+, 255 (24.2), 179 (30.4), 178
(38.4), 77 (7.8).
A series of preliminary experiments showed that the
yields of the transformation products of two acetylene
molecules in three-component coupling reactions
(compounds 3–5) can be controlled within wide limits
(Scheme 1). For example, raising the temperature from
80 to 140 ° C allowed fairly selective synthesis of
product 3 in yields of up to 70%. The use of a reducing
agent (sodium formate) expectedly significantly
increased the yield of reduction product 4, while the
use of aqueous DMF as a solvent increased the
selectivity in product 5 (up to 20%).
1-(4-Methoxyphenyl)-1,2-diphenylethene (1b).
Mass spectrum, m/z (Irel, %): 286 (100.0) [M]+, 285
(10.2), 255 (10.3), 178 (10.88), 165 (16.8), 77 (4.1).
1,1,2,2-Tetraphenylethene (2а). Mass spectrum,
m/z (Irel, %): 332 (100.0) [M]+, 255 (15.4), 254 (14.5),
253 (23.9), 252 (14.5).
2-(4-Methoxyphenyl)-1,1,2-triphenylethene (2b).
Mass spectrum, m/z (Irel, %): 362 (100.0) [M]+, 253
(12.9), 241 (10.4), 239 (8.9).
2-(4-Metylphenyl)-1,1,2-triphenylethene (2c).
Mass spectrum, m/z (Irel, %): 346 (100.0) [M]+, 269
(8.8), 255 (11.1), 254 (16.1), 253 (29.6), 252 (20.0).
Thus, our present results provide evidence showing
that three-component coupling catalyzed by simple
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 5 2019

POLYAROMATIC PRODUCTS OF THREE-COMPONENT COUPLING OF ARYL HALIDE
681
1,2,3,4-Tetraphenylnaphthalene (3а). Mass
spectrum, m/z (Irel, %): 432 (100.0) [M]+, 355 (14.6),
354 (8.7), 339 (10.4), 177 (10.0).
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The work was funded by the Ministry of Education
and Science of the Russian Federation in the
framework of the basic part of the State order for
scientific research (project no. 4.9489.2017/8.9) and
Russian Foundation for Basic Research (project no.
18-33-00362 mol_a).
CONFLICT OF INTEREST
The authors declare no conflict of interest.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 55 No. 5 2019