Arylhydrazones Derivatives Containing a Benzothiazole Moiety, Efficient Ligands in the Palladium-Catalyzed Mizoroki–Heck and Suzuki–Miyaura Cross-coupling Reactions under IR Irradiation

Article abstract of DOI:10.1002/cjoc.201700390

A simple arylhydrazone containing the benzothiazole moiety which may be used as an efficient ligand in the palladium-catalyzed Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions, under infrared irradiation as an alternative source of energy, is presented. The reactions proceeded with extremely high efficiency under mild conditions and produced very good yields.

Full text of DOI:10.1002/cjoc.201700390

Arylhydrazones derivatives containing a benzothiazole moiety,
efficient ligands in the palladium-catalyzed Mizoroki-Heck and
Suzuki-Miyaura cross-coupling reactions under IR irradiation
a
a
Fernando Ortega-Jiménez* , José Guillermo Penieres-Carrillo , José Guadalupe
b
c
d
López-Cortés , M. Carmen Ortega-Alfaro and Selene Lagunas-Rivera
a
Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán-UNAM, Campo 1, Avenida 1ro.
de Mayo s/n, Cuautitlán Izcalli, C.P. 54740, Estado de México, México.
Instituto de Química UNAM, Circuito Exterior, Ciudad Universitaria, Coyoacán C.P. 04360, Cuidad de México,
b
México
Instituto de Ciencias Nucleares, UNAM, Circuito Exterior, Ciudad Universitaria, Coyoacán C.P. 04360, Ciudad
de México, México.
Catedrático CONACyT-TecNM- Instituto Tecnológico de Tuxtla Gutiérrez. Carretera Panamericana Km 1080.
Col Juan Crispin. Tuxtla Gutiérrez C.P. 29050,Chiapas. México.
c
d
A simple arylhydrazone-containing the benzothiazole moiety which may be used as efficient ligand in the palladi-
um-catalyzed Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions, under infrared irradiation as an alterna-
tive source of energy, is presented. The reactions proceeded with extremely high efficiency under mild conditions
and produced very good yields.
Keywords Arylhydrazones, Palladium-catalyzed, Cross-coupling reaction, IR-irradiation
Introduction
generally advantageous because they usually are stable
to air, inexpensive and easier to handle than their phos-
The Mizoroki-Heck reaction is one of the most gen-
eral and useful method for the formation of C-C bonds.
This coupling reaction has a wide variety of applications,
[15]
[16]
phine counterparts. including NHC ligand.
On the other hand, new alternative heating method-
[17]
[18]
ologies such as microwave, ultrasound, and infra-
red (IR) irradiation
[
1]
including total synthesis of natural products, fine
[19]
have been applied in organic
[
2]
[3,4]
chemical syntheses, bioorganic chemistry,
material
synthesis and catalysis with reduced reaction times,
cleaner reaction mixtures and good yields. We aimed to
develop an environmentally safe method, and recently
reported the use of IR irradiation as the energy source in
[5]
[6]
science and industrial applications, among others.
Furthermore, the palladium-catalyzed Suzuki-Miyaura
[
7]
cross-coupling is another very useful and convenient
method especially for the synthesis of various biaryl
[20]
[21]
Mizoroki-Heck
and
Suzuki-Miyaura
[
8,9]
compounds
found as important structural units in
cross-coupling reactions; in addition we demonstrated
an air-stable phosphine-free hydrazone containing a
heterocycle moiety as an effective ligand for palladi-
um-catalyzed Mizoroki-Heck cross-coupling under IR
[10] [11]
pharmaceuticals
and natural products.
Conse-
quently, researchers have been working on developing
better catalysts and increasing yields in these areas
which are important for both industrial and scientific
[20]
irradiation.
[12]
purposes.
For this, we are interested on the development of a
simple and active catalyst system to promote Mizoro-
ki-Heck and Suzuki-Miyaura cross-coupling reactions,
and focus our attention on arylhydrazones because their
structure is simple and very stable. We are also inter-
ested on extending the use of IR irradiation as an alter-
native energy source for coupling reactions. Because of
the above, herein we report the synthesis of arylhydra-
zone derivatives containing the benzothiazole moiety as
the effective ligand for palladium-catalyzed Mizoro-
In Mizoroki–Heck and Suzuki–Miyaura reactions,
phosphine compounds are active due to their excellent
donor capability.
pounds present some disadvantages such as natural tox-
icity, sensitivity to air, being expensive, exhibiting syn-
thetic difficulties and limitations of use,
opment of new more robust based-on-ligands and/or
phosphine-free catalytic systems, based on different
ligands that contain different donor groups, has been
favored. Within this scope, nitrogen-based ligands are
[
13]
Nevertheless, because these com-
[
14]
the devel-
*
Email address; fdo.ortega@unam.mx Tel.: +52-555-623-2024; Fax: +52-555-623-2024
Received ((will be filled in by the editorial staff)); revised ((will be filled in by the editorial staff)); accepted ((will be filled in by the editorial staff)).
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.2011xxxxx or from the author. ((Please delete
if not appropriate.)).
This article has been accepted for publication and undergone full peer review but has not
been through the copyediting, typesetting, pagination and proofreading process, which
may lead to differences between this version and the Version of Record. Please cite this
article as doi: 10.1002/cjoc.201700390
This article is protected by copyright. All rights reserved.

ki-Heck and Suzuki-Miayaura cross-coupling reactions
using IR irradiation.
H-14, H-15, H4, H-5), 7.76 (s, 1H, H-10), 7.83 (d, J =
9.0 Hz, 1H, H-6), 7.93 (d, J = 9.0 Hz, 1H, H-3,);
C-NMR (CDCl3, 75 MHz) δ: 34.2 (CH N), 116.3
3
13
(
(
(
ν
C-14), 121.7 (C-16), 122.7 (C-3), 125.4 (C-6), 126.2
C-4), 126.3 (C-5), 129.4 (C-15), 129.5 (C-10), 134.3
C-7), 146.7 (C-13), 153.8 (C-2), 168.3 (C-9); IR (KBr)
Experimental
Apparatus, Materials, and Measurements
-
1
All operations were carried out in open atmosphere.
Column chromatography was performed using 70–230
mesh silica gel. All reagents and solvents were obtained
from commercial suppliers and used without further
purification. All compounds were characterized by IR
spectra, recorded on a Perkin-Elmer 283B by, Per-
kin-Elmer 283B or 1420 spectrophotometer, by means
of film and KBr techniques, and all data are expressed
:
3034, 2967, 2933, 1608, 1711, 1458, 1435 cm ; MS
+
(
2
DART) m/z (%): 268 (98, M + H).
-Benzothiazolecarboxaldehyde N-phenylhydrazone 1c.
(
560 mg, 85 %) as yellow crystals, mp 202-204 °C (lit
[
22]
1
2
04-205 °C). H-NMR (CDCl3, 300 MHz) δ: 3.21 (s,
1
H, N-H), 7.00-7.06 (m, 1H, H-16), 7.28-7.37 (m, 5H,
H-10, H-14, H-15), 7.43 (t, J = 14.7 Hz, H-4,), 7.52 (t, J
=
=
1
1
1
14.7 Hz, 1H, H-5), 7.82 (d, J 8.1, 1H, H-6), 8.07 (d, J
-1
13
in wave numbers (cm ). Melting points were obtained
on a Melt- Temp II apparatus and are uncorrected. NMR
spectra were measured with a Varian Eclipse +300 us-
8.1 Hz, 1H, H-3,); C-NMR (CDCl3, 75 MHz) δ:
13.8 (C-14), 120.1 (C-3), 120.9 (C-6), 122.9 (C-16),
25.8 (C-4), 126.3 (C-5), 126.6 (C-10), 129.4 (C-15),
ing CDCl as solvents. Chemical shifts are in ppm (δ),
3
34.2 (C-7), 142.2 (C-13), 153.6 (C-9), 167.3 (C2); IR
2
relative to TMS. The MS-EI and MS-DART spectra
were obtained on a JEOL SX 102A, the values of the
signals are expressed in mass/charge units (m/z), fol-
lowed by the relative intensity with reference to a 100%
base peak.
(
(
KBr) ν
:
3060, 3027, 2994 (H-Csp ), 1711 (C=N), 1711
-
1
C=NHet), 1632 (C=CAr) cm ; MS (DART) m/z (%):
+
2
54 (98, M + H).
General synthetic procedure for de compounds 2a-f.
A solution of the corresponding substituted benzalde-
The equipment used for irradiation with IR energy
was created by employing an empty cylindrical metal
vessel in which an Osram lamp (bulb model The-
hyde (2.6 mmol) in methanol (5 mL) was added drop-
wise to magnetically stirred solution of
-hydrazinobenzothiazole (2.6 mmol) in methanol (5
mL). The mixture was stirred at room temperature for
0 min, to give a solid, which was recovered by filtra-
a
2
[20,21]
ra-Therm, 250 W, 125 V) was inserted.
This lamp
is special short-wave IR lamp (IR-A) for use in body
care and wellness applications, with a maximum radia-
tion at a wavelength of about 1100 nm. The lamp in-
stantly emits a full thermal output as soon as it is
switched on. For controlling the temperature, a Di-
gi-Sense variable-time power controller was used. This
time controller turned the output load on and off and
then repeated the cycle. Although all the reactions were
performed in open atmosphere, this arrangement also
allows the use of inert conditions.
3
tion and recrystallized from methanol.
Benzaldehyde 2-(2-benzothiazolyl)hydrazone 2a. (630
mg, 96 %) as white crystals, mp 226-228 °C (lit
2
N-H), 7.29-7.35 (m, 2H, H-14), 7.42-7.49 (m, 3H, H-15,
H-16), 7.64-7.74 (m, 4H, H-3, H-5, H-6), 8.40 (s, 1H,
H-12); C-NMR (CDCl3, 75 MHz) δ: 116.0 (C-3),
1
1
1
1
[23a]
1
25-226 °C). H-NMR (CDCl3, 300 MHz) δ: 6.8 (s, 1H,
13
22.0 (C-6), 124.5 (C-5), 127.8 (C-15), 128.9 (C-14),
31.3 (C-16), 132.5 (C-13), 140.2 (C-12), 150.8 (C-2),
General synthetic procedure for de compounds 1a-c.
A solution of the corresponding phenylhydrazine
60.3 (C-9); IR (KBr) ν
:
3056, 2964, 1921, 1881, 1805,
-
1
625, 1632, 1575 cm ; MS (DART) m/z (%): 254 (98,
+
(
2.6 mmol) in methanol (5 mL) was added dropwise to a
M + H).
4
2
magnetically stirred solution of benzothia-
-Methylbenzaldehyde 2-(2-benzothiazolyl)hydrazone
zol-2-carbaldehyde (2.6 mmol) in methanol (5 mL). The
mixture was stirred at room temperature for 12 h, to
give a yellow solid, which was recovered by filtration
and recrystallized from methanol.
b. (620 mg, 90 %) as yellow crystals, mp 232-234 °C
[
23a]
1
(
lit
231-233 °C). H-NMR (CDCl3, 300 MHz) δ:
2
3
.39 (s, 3H, CH ), 7.23 (d, J = 8.1 Hz, 2H, H-15), 7.40 (t,
J =14.4 Hz, 2H, H-4, H-5), 7.61 (d, J = 8.1 Hz, 2H,
H-14), 7.67, (d, J = 7.5 Hz, 2H, H-6), 8.31 (s, 1H, H-12)
9
2
-Benzothiazolecarboxaldehyde N,N-diphenylhydrazo–
13
ne 1a. (820 mg, 90 %) as yellow crystals, mp
.36 (s, 1H, N-H); C-NMR (CDCl3, 75 MHz) δ: 21.6
1
1
(
42-144 °C; H-NMR (CDCl3, 300 MHz) δ: 7.21-7.25
m, 4H, H-14), 7.26 (s, 1H, H-10), 7.33-7.38 (m, 2H,
H-16), 7.40-7.46 (m, 6H, H-15, H-4, H-5), 7.83-7.88 (m,
2
(
(
(
(
CH ), 116.3 (C-3), 121.8 (C-6), 123.95 (C-5), 125.7
3
C-4), 127.4 (C-7), 127.6 (C-14), 129.5 (C-15), 130.1
C-13), 141.5 (C-16), 142.1 (C-12), 149.6 (C-2), 168.2
C-9); IR (KBr) ν: 3202, 3076, 2886, 2814, 1916, 1878,
1
3
H, H-6, H-3); C-NMR (CDCl3, 75 MHz) δ: 121.5
C-3), 122.3 (C-6), 122.6 (C-14), 125.5 (C-10), 125.9
C-4), 129.6 (C-5), 129.9 (C-15, C-16), 134.2 (C-7),
(
-1
+
1
624, 1577 cm ; MS (DART) m/z (%): 268 (98, M +
(
H).
-Methoxylbenzaldehyde
zone 2c. (710 mg, 97 %) as white crystals, mp
1
3
42.2 (C-13), 153.6 (C-2), 167.3 (C9); IR (KBr) ν
:
3060,
4
2-(2-benzothiazolyl)hydra-
-
1
027, 2994, 1711, 1711, 1632 cm ; MS (70 eV) m/z
+
[
23a]
1
(
2
%):329 (M , 98), 168 (100).
-Benzothiazolecarboxaldehyde N-methyl-N-phenylhy-
drazone 1b. (600 mg, 85 %) as yellow crystals, mp
1
96-198 °C (lit
MHz) δ: 3.85 (s, 3H, OCH
J = 8.7 Hz, 2H, H-15), 7.20 (t, J = 14.1 Hz, 1H, H-4),
.36 (t, J = 14.1 Hz, 1H, H-5), 7.55 (d, J = 7.5 Hz, 2H,
H-6), 7.64 (d, J = 8.7 Hz, 2H, H-14), 8.18 (s, 1H, H-12).
194-195 °C). H-NMR (CDCl3, 300
3
), 6.97 (s, 1H, N-H), 6.93 (d,
1
1
50-152 °C; H-NMR (CDCl3, 300 MHz) δ: 3.45 (s, 3H,
7
CH -N), 7.02-7.08 (m, 1H, H-16), 7.33-7.43 (m, 6H,
3
This article is protected by copyright. All rights reserved.

1
3
1
13
C-NMR (CDCl3, 75 MHz) δ: 55.3 (OCH
3
), 114.2
determination and by H and C-NMR; the data ob-
[24]
(C-15), 116.6 (C-3), 121.7 (C-6), 123.1 (C-5), 126.0
(C-4), 126.9 (C-7), 127.2 (C-13), 129.0 (C-14), 144.7
(C-12), 147.5 (C-2), 161.6 (C-16), 168.2 (C-9); IR (KBr)
tained are consistent with literature.
General procedure for Suzuki-Miyaura coupling re-
actions
Inside a 50-mL round-bottom flask, a mixture of aryl
halide (0.5mmol), phenylboronic acid (0.6 mmol), and
base (1 mmol) was placed in 3 mL of solvent; then,
-
1
ν: 3063, 3000, 2931, 2832, 1603, 1574, 1557 cm ; MS
+
(
DART) m/z (%): 284 (98, M + H).
-Dimethylaminolbenzaldehyde
yl)hydrazone 2d. (745 mg, 97 %) as white crystals, mp
4
2-(2-benzothiazol-
Pd(OAc)
2
and hydrazone 1a were added. The reaction
was irradiated with IR energy
[
23a]
1
[20,21]
2
38-240 °C (lit
236-238 °C). H-NMR (CDCl3, 300
), 6.72 (d, J = 8.7 Hz, 2H,
for the time reported
MHz) δ: 3.01 (s, 6H, NMe
H-15), 7.13 (t, J = 14.1 Hz, 1H, H-4), 7.33 (t, J = 14.1
Hz, 1H, H-5), 7.51 (d, J = 7.8 Hz, 2H, H-6), 7.54 (d, J =
8
1
1
2
in Tables 3 and 4. Thereafter, the reaction was cooled at
room temperature; the mixture was diluted with 10 mL
of water and extracted with hexane or AcOEt (3 X 10
mL). The combined organic layers were dried over an-
hydrous sodium sulfate. The crude product was finally
purified by column chromatography on silica-gel to give
the isolated products.
.7 Hz, 2H, H-14), 7.68 (d, J = 7.8 Hz, 1H, H-3), 7.91 (s,
H, H-12). C-NMR (CDCl3, 75 MHz) δ: 40.2 (NMe
11.5 (C-15), 117.8 (C-3), 121.3 (C-6), 121.6 (C-5),
21.9 (C-13), 125.9 (C-4), 128.3 (C-14), 130.2 (C-7),
44.9 (C-12), 150.0 (C-2), 151.5 (C-16), 168.3 (C-9);
13
2
),
1
1
The purified product was identified by means of mp
1
13
IR (KBr) ν: 3074, 3040, 2883, 2799, 1920, 1877, 1624,
1
determination and by H and C-NMR; the data ob-
-
1
+
[25]
576, 1556 cm ;. MS (DART) m/z (%): 297 (98, M +
tained are consistent with literature.
H).
4
-Cholorobenzaldehyde 2-(2-benzothiazolyl)hydrazone
Results and discussion
2
e. (720 mg, 97 %) as white crystals, mp 143-145 °C (lit
[
23b]
1
We carried out the synthesis of two arylhydrazone
derivatives containing the benzothiazole moiety, com-
pounds 1 and 2 (Figure 1).
1
40-142 °C). H-NMR (CDCl3, 300 MHz) δ: 7.20 (t,
J 14.1, 2H, H-4, H-5), 7.35 (d, J = 7.2 Hz, 1H, H-3),
7
.40 (d, J = 8.4 Hz, 2H, H-15), 7.55 (d, J = 7.8 Hz, 1H,
H-6), 7.65 (d, J = 8.4 Hz, 2H, H-14), 7.8 (s, 1H, H-12).
1
3
C-NMR (CDCl3, 75 MHz) δ: 118.3 (C-3), 121.8 (C-6),
24.5 (C-5), 125.3 (C-4), 128.9 (C-15), 130.6 (C-14),
30.8 (C-7), 134.9 (C-13), 136.6 (C-16), 143.3 (C-12),
50.1 (C-2), 169.8 (C-9); IR (KBr) ν: 3078, 2965, 1931,
1
1
1
1
(
4
-1
884, 1626, 1575, 1489 cm ; MS (DART) m/z (%): 288
+
98, M + H).
-Nitrobenzaldehyde 2-(2-benzothiazolyl)hydrazone 2f.
770 mg, 99 %) as yellow crystals, mp 118-120 °C (lit
(
[
23b]
1
1
17-119 °C). H-NMR (CDCl3, 300 MHz) δ: 7.14 (t,
J = 14.1 Hz, 2H, H-3), 7.60-7.67 (m, 2H, H-4, H-6),
.85 (d, J = 9.0 Hz, 2H, H-14), 7.95-7.96 (m, 2H, H-5,
Figure 1 Structure of arylhydrazones.
7
13
The syntheses of arylhydrazones 1a-c were achieved
by the reaction of benzothiazol-2-carbaldehyde with the
corresponding arylhydrazine in methanol for 12 h ob-
taining good yields. Arylhydrazones 2a-f were synthe-
tized by the reaction of 2-hydrazinobenzothiazole with
the appropriate substituted benzaldehyde in methanol
for 30 min obtaining excellent yields.
H12), 8.0 (d, J = 8.4 Hz, 2H, H-15). C-NMR (CDCl3,
7
1
1
1
1
5 MHz) δ: 116.9 (C-3), 121.7 (C-6), 123.1 (C-15),
23.2 (C-14), 126.0 (C-5), 126.9 (C-4), 127.2 (C-7),
29.0 (C-13), 144.7 (C-12), 147.5 (C-2), 161.6 (C-16),
68.2 (C-9); IR (KBr) ν: 3073, 2966, 1936, 1893, 1623,
-
1
+
570, 1510 cm ; MS (DART) m/z (%): 299 (98, M +
H).
Compounds 1 and 2 were fully characterized by con-
General procedure for Mizoroki–Heck coupling re-
actions
A mixture of aryl halide (2 mmol), methyl acrylate
3.3 mmol), and base (2.5 mmol) was placed in 5 mL of
1
ventional spectroscopic methods, FT-IR, H-NMR, and
1
3
C-NMR, and the data spectra are in full accordance
[
22,23]
with previous reports.
Compared with some previous results,
(
[
23]
we ob-
solvent in a 50-mL round-bottom flask; then, the source
served that the syntheses of arylhydrazones 2a-f can be
performed at room temperature, with short reaction
times, and without the use of reflux or acid catalysis.
Once efficiently prepared arylhydrazones 1a-c and
of palladium and the corresponding arylhydrazone, 1 or
2
, were added. The reaction mixture was irradiated with
[20,21]
IR energy
for the time reported in Tables 1 and 2.
The reaction was thereafter cooled at room temperature
and the mixture was diluted with 10 mL of water and
extracted with either ether or hexane (3 X 10 mL). The
combined organic layers were dried over anhydrous
sodium sulfate. The crude product was finally purified
by flash column chromatography on silica-gel to give
the isolated products.
2
a-f they were used as ligands in the palladi-
um-catalyzed Mizoroki-Heck reaction under IR irradia-
tion as a source of energy. We chose Pd(OAc) and 1a
2
as model pre-catalyst and we firstly evaluated the effect
of the concentration of the catalytic system
[
(
Pd(OAc)
2
/1a] on the reaction between 4-iodotoluene
3a) and methyl acrylate (4) (Table 1)
The purified product was identified by means of mp
This article is protected by copyright. All rights reserved.

a
Table 1 Optimization of conditions for the Mizoroki-Heck cross-coupling reaction.
d
Entry
Ligand
Source of
Base
Solvent
Time
Yield
TON
TOF
b
c
-1 e
(
% mol)
Pd (% mol)
(min)
90
(%)
(h )
1
2
3
4
5
6
7
8
9
1a (0.5)
Pd(OAc)
2
2
(0.5)
(0.1)
K
K
K
K
3
3
3
3
PO
PO
PO
PO
4
4
4
4
DMF
DMF
DMF
DMF
DMA
NMP
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
70
65
85
83
90
85
60
50
75
76
80
70
87
85
80
84
80
85
87
86
85
10
0
200
650
133
433
1a (0.1)
Pd(OAc)
90
1a (0.05)
1a (0.01)
1a (0.05)
1a (0.05)
1a (0.05)
1a (0.05)
1a (0.05)
1a (0.05)
1b (0.05)
1c (0.05)
2a (0.05)
2b (0.05)
2c (0.05)
2d (0.05)
2e (0.05)
2f (0.05)
1a (0.05)
1a (0.05)
1a (0.05)
None
Pd(OAc)
Pd(OAc)
2
2
(0.05)
(0.01)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
(0.05)
60
1700
8300
1800
1700
1200
1000
1500
1520
1600
1400
1740
1700
1600
1680
1600
1700
1740
1720
1700
200
1700
1660
1800
1700
1200
250
300
60
Pd(OAc)
2
K
3
PO
PO
PO
PO
CO
KOAc
4
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
2
K
3
4
60
2
Na
3
4
60
2
2
2
2
2
2
2
2
2
2
2
Li
3
4
240
90
K
2
3
1000
1013
1600
1400
1740
850
10
11
12
13
14
15
16
17
18
19
20
21
22
23
90
K
K
K
K
K
K
K
K
K
K
K
K
K
K
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
3
PO
4
4
4
4
4
4
4
4
4
4
4
4
4
4
60
60
60
120
60
1600
1680
1066
850
60
90
120
90
PdCl
Pd(PhCN)
Pd(PPh
Pd(OAc)
None
Pd(OAc) (0.05)
2
(0.05)
1160
1720
1700
200
Cl
2 2
(0.05)
60
3
)
Cl
2 2
(0.05)
60
2
(0.05)
60
1a (0.05)
1a (0.05)
0
0
0
f
2
4
2
360
90
1800
300
a
b
Reaction conditions: 4-iodotoulene (1 mmol), methyl acrylate (2 mmol), base (2 mmol), 5 mL solvent, reflux. Based on total consump-
c
d
e
tion of aryl iodide determined by TLC. Isolated yields. TON = ratio of moles of product formed to moles of catalyst used. TOF =
TON/t (h). Employing heating blanket.
f
.
The coupling reaction was stirred under reflux, using
different concentrations of the [Pd(AcO) /1a] system
and different solvents (DMF, DMA and NMP); also,
different bases, such as K PO , Na PO , Li PO , K CO
and KOAc, were evaluated (entries 1-10, Table 1). The
best yield was obtained when DMA, K PO , and 0.05 %
mol of the [Pd(OAc) /1a] system were used (entry 5,
Table 1). Under similar conditions, the cross-coupling
reaction was carried out using ligands 1b-c (entries 11
and 12, Table 1) and 2a-f, that afforded 5a (entries
13-18, Table 1) though yielded less. Thus, hydrazone 1a
provides better performance in comparison to others
compounds, with turn over numbers (TON) around
2
3
4
3
4
3
4
2
3
,
3
3
4
~10 .
2
Once the best catalyst and the appropriate solvent
were identified, different palladium sources (entries
*
Email address; fdo.ortega@unam.mx Tel.: +52-555-623-2024; Fax: +52-555-623-2024
Received ((will be filled in by the editorial staff)); revised ((will be filled in by the editorial staff)); accepted ((will be filled in by the editorial staff)).
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.2011xxxxx or from the author. ((Please delete
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1
9-21, Table 1) were tested and 5a was obtained with
the coupling product in absence of ligand but in a low
yield (entry 22, Table 1). Afterwards, in order to com-
pare the energy sources, conventional heating (entry 24,
Table 1) was used, which increased the reaction time in
comparison with the use of IR heating.
good yields; however, these yields did not exceed the
efficiency of entry 5. Furthermore, we conducted two
additional experiments; the first one was performed in
absence of ligand and the second experiment was per-
formed in absence of Pd(OAc)
2
(entries 22 and 23, Ta-
ble 1). As expected, we only observed the formation of
a
Table 2 Scope of Mizoroki-Heck cross-coupling of aryl halides and methyl acrylate under IR irradiation.
b
c
d
Entry
X
R
3
Product
Time (min)
Yield (%)
TON
TOF
-
1 e
(
h )
1
2
3
4
5
6
7
8
9
I
I
4-CH
2-CH
3
3
5a
5b
5c
5d
5e
5f
60
70
90
90
94
90
85
80
85
80
75
80
10
85
80
90
85
90
65
80
50
70
1800
1800
1880
1800
1700
1000
1400
1600
900
1800
1551
3760
3600
1700
200
I
4-OCH
3
30
I
4-NH
2
30
I
H
60
I
4-Ac
4-Br
300
60
I
5g
5h
5i
1400
3200
150
I
4-AcO
30
I
4-NO
2
360
420
120
60
1
0
1
I
4-CF
4-CH
4-CH
2-CH
3
5j
1600
200
228
1
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
3
3
3
5a
5a
5b
5c
5d
5e
5f
100
f
12
1800
1600
1880
1800
1700
1000
1600
900
1800
533
1
3
180
60
f
f
f
f
f
f
f
1
1
1
1
1
1
2
4
4-OCH
3
3760
3600
1700
200
5
6
7
8
9
0
4-NH
2
60
H
90
4-Ac
4-AcO
150
120
300
90
5h
5i
3200
150
4-NO
4-Cl
2
5k
1400
1400
a
b
Aryl halide (2 mmol), methyl acrylate (4) (3.3 mmol), DMA (5 mL), K
3
PO
consumption of aryl iodide determined by TLC. Isolated yields after SiO column chromatography. TON = ratio of moles of product
formed to moles of catalyst used. TOF = TON/t (h). Used TBAB (40%) as additive and 1 % mol of [Pd(OAc) /1a] system.
4 2
(2.5 mmol), [Pd(AcO) /1a] = 0.05 % mol. Based on total
c
d
2
e
f
2
The next step was to explore the scope for the Mi-
zoroki-Heck reaction in order to afford methyl
trans-cinnamates 5a-k. In this context, we carried out
the reaction with a variety of activated and deactivated
aryl iodides (3a-j) and aryl bromides (6a-i,k) with me-
the reaction condition and, thus, used TBAB as additive,
2
and 1 % mol of the [Pd(OAc) /1a] system (entries 12-20,
Table 2).
This study shows that the Mizoroki-Heck reaction
can be carried out using IR irradiation as a heating
source to reduce reaction times and increase the effi-
ciency of the reaction.
thyl acrylate (4), using the [Pd(OAc)
catalyst (Table 2). However, the coupling reaction of
-bromotoluene (6a) and methyl acrylate (3), produced
2
/1a] system as the
4
To extend the study of the catalytic properties of the
methyl trans-cinnamate 5a in a very low yield in 120
2
[Pd(AcO) /1a] system, we performed a series of ex-
min (entry 11, Table 2). As a result, we had to improve
periments using the Suzuki-Miyuara cross-coupling re-
This article is protected by copyright. All rights reserved.

action (Table 3). The coupling reaction between
-bromoanisole and phenylboronic acid was selected as
a model reaction. The approach used for the proposed
Mizoroki–Heck reaction was also followed for the Su-
zuki–Miyaura reaction. In a first attempt, we used 0.05 %
2
mol of the [Pd(AcO) /1a] system in methanol/water 3
mL (1:1) (entry 1, Table 3) using IR as the energy
source for the optimization of conditions.
4
a
Table 3 Optimization of the conditions for the Suzuki-Miyaura cross-coupling reaction using the [Pd(OAc)
2
/1a] system.
l
Entry
Catalyst
Base
Solvent
Time
Yield
TON
TOF
j
k
-1 m
[
Pd(AcO)
2
/1a] (%)
(min)
15
(%)
(h )
b
b
b
b
b
b
c
1
2
3
4
5
6
7
8
0.05
0.01
0.001
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
K
K
K
3
3
3
PO
PO
PO
4
4
4
MeOH/H
2
2
2
2
2
2
O (1:1)
99
99
80
99
99
60
99
99
99
99
99
99
80
45
0
1980
9900
80000
9900
9900
6000
9900
9900
9900
9900
9900
9900
9900
4500
0
7920
39600
160000
9900
MeOH/H
MeOH/H
MeOH/H
MeOH/H
MeOH/H
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
15
30
K
2
CO
3
60
KOH
30
19800
9090
KOAc
40
K
K
3
PO
PO
4
4
MeOH/H
2
O (1:1)
15
39000
39600
39600
24146
30000
9900
d
3
MeOH
15
e
10
K
3
PO
4
H
2
O
15
f
11
K
K
K
K
K
K
3
PO
PO
PO
PO
PO
PO
4
EtOH
25
g
12
13
14
15
16
3
3
3
3
3
4
EtOH/H
2
O (1:1)
20
h
4
4
4
4
H
2
O
60
i
H
2
O
1020
120
120
582
n
H
2
2
O
O
2250
o
H
0
a
b
c
4
-Bromoanisole 6b (0.5 mmol), phenylboronic acid (7) (0.6 mmol), solvent (3 mL), Base (1 mmol), TBAB 0.5 mol. T = 75 °C. The
d
e
f
g
h
reaction was conducted in absence of TBAB T = 75 °C. T = 65 °C. T = 96 °C. T = 78 °C. T = 82 °C. Under conventional heating T
=
umn chromatography. TON = ratio of moles of product formed to moles of catalyst used. TOF = TON/t (h). Without ligand. Without
Pd sourse.
i
j
k
2
96 °C. Under room temperature. Based on total consumption of 4-bromoanisole determined by TLC. Isolated yields after SiO col-
l
m
n
o
We evaluated the effect of the concentration of the
catalytic system on the reaction between
-bromoanisole and phenylboronic acid (entry 1-3, Ta-
ble 3). To find this optimum concentration, the reaction
was carried out with different bases (entries 4-6, Table
volve the use of 0.01% mol catalyst system
[Pd(OAc)2/1a], K PO as the base, and H O as the sol-
vent in absence of TBAB under IR-irradiation (entry 10,
Table 3).
Finally, we conducted two additional experiments;
the first one was performed in absence of ligand and the
second experiment was performed in absence of
3
4
2
4
3
3 4
). We observed excellent yields using K PO in the
absence of TBAB (entry 7; Table 3); different solvent
systems were tested, (entries 8-12, Table 3).
2
Pd(OAc) (entries 15 and 16, Table 3). As expected, we
Furthermore, to compare the energy sources, the re-
action at reflux conditions under conventional heating
was tested (entry 13, Table 3), obtaining a quantitative
yield of the coupling product of 8b. The same reaction
was performed at room temperature and produced 76%
yield of 8b, in 7 h (entry 14, Table 3). Thus, the opti-
mized conditions for this cross-coupling reaction in-
only observed the formation of the coupling product in
absence of ligand but in a longer time and lower yield
(entry 15, Table 3).
Subsequently, catalytic experiments were conducted
with various aryl halide and boronic acid derivatives
(entries 1-14, Table 4), including two heterocyclic sub-
strates as a representative examples (entries 15 and 16,
This article is protected by copyright. All rights reserved.

Table 4). In every case, the substrates were quantita-
tively converted to the corresponding biphenyl, in gen-
eral with good to excellent isolated yields after purifica-
tion. The results showed that the catalytic system
system promotes the C-Cl bond activation but is moder-
ately efficient compared to other aryl halides.
In order to compare other sources of palladium in the
[
20a]
Mizoroki-Heck coupling, we previously reported
the
[
Pd(OAc)
2
/1a] is active with a wide range of substitu-
use of this methodology with different commercial pal-
ladium compounds in combination with tri-
phenylphosphine due to this is the most used ligand in
this reaction.
ents, and good yields of the coupling product were ob-
tained. In spite of the reactivity of 4-chlorotoluene in the
same reaction conditions (entry 5, Table 4), the catalytic
a
Table 4 Scope of Suzuki-Miyaura cross-coupling of aryl halides and phenyl boronic acids under IR irradiation.
b
c
e
-1 f
Entry
X
I
Ar
R
4
Product
8a
Time (min)
Yield (%)
99
TON
TOF (h )
1
2
3
4
5
6
7
4-CH
3
3
3
3
3
C
6
6
6
6
6
H
H
H
H
H
5
5
5
5
5
H
H
15
20
15
30
60
15
30
30
15
15
15
15
15
40
60
120
9900
9600
9900
9500
1500
9900
9000
7500
9700
9900
9900
8500
9900
9900
5500
6000
39600
2909
I
2-CH
4-CH
2-CH
4-CH
C
C
C
C
8b
8a
96
Br
Br
Cl
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
H
99
39600
19000
1500
H
8b
8a
95
H
15
4-OCH
3
6
C H
5
H
8c
99
39600
18000
15000
38800
39600
39600
34000
39600
15000
5500
C
6
H
5
H
8d
8e
90
d
8
10
C H
8
H
75
9
4-ClC
4-AcC
4-NO
6
H
5
H
8f
97
10
6
H
5
H
8g
8h
8i
99
11
2
C
6
H
5
H
99
12
13
14
15
16
4-OCH
4-OCH
4-OCH
3
3
3
C
6
C
6
C
6
H
5
5
5
CH
3
85
H
H
Cl
8j
99
NO
H
2
8k
8l
99
2-Pyridine
2-Thiophene
55
H
8m
60
3000
a
b
Aryl halide 6 (0.5 mmol), phenylboronic acid (7) (0.6 mmol), H
2 3
O (3 mL), K PO
4 2
(1 mmol), ), [Pd(AcO) /1a] = 0.01 % mol, T = 96 °C
c
Based on total consumption of aryl halide determined by TLC. Isolated yields after extraction with hexane and SiO
graphy. 1-Bromonaphtalene was used as starting material. TON = ratio of moles of product formed to moles of catalyst used. TOF =
TON/t (h).
2
column chromato-
d
e
f
These previously reported results show that the sys-
tem formed by Pd(AcO) /PPh /K PO can be considered
the most efficient catalytic system, however our results
herein presented are similar to these results. Moreover,
compared to other ligands in the Mizoroki-Heck cou-
pling previously reported, our protocol using the
organic solvent at high temperature and/or under an in-
[31,32,33-35]
2
3
3
4
ert atmosphere.
der aerobic conditions at room temperature can be ac-
complished by using a simple amine/Pd(OAc) or gly-
oxal bis(N-methyl-N-phenylhydrazone)/Pd(OAc) sys-
with a Pd loading as high as 2 mol % and the
reaction time is longer. In addition the use of Pd(AcO)
and PdCl –free ligands to carry out such coupling is
Suzuki-Miyaura reactions un-
2
2
[
36, 37a]
tem
[
Pd(OAc)
2
/arylhidrazone] system shows important ad-
2
-
[
26]
vantages in terms of lower reaction times, lower cat-
alytic system loading,
phere. These advantages also exceed the results ob-
tained by studies where the Mizoroki-Heck reaction was
carried out in the absence of ligands using various pal-
2
[27]
and the use of open atmos-
also reported, the results show good efficiency of the
catalytic system, reaction at room temperature and good
[
28]
[34]
yields.
However, palladium loads are usually used
above 0.5 mol% and the system only works well with
electron donor groups on the arylhalide.
[
29,30]
ladium sources.
Regarding the Suzuki-Miyaura coupling, many
N-based compounds have been reported to be efficient
ligands, in most cases the reactions were carried out in
Furthermore, in comparison to other studies on the
Suzuki-Miyaura coupling reaction available in the liter-
ature, the present reaction protocol is advantageous in
This article is protected by copyright. All rights reserved.

[
38]
terms of arylboronic acid loading, lower reaction
[36,37,39a,40]
omet. Chem. 2015, 29, 543; (b) Bumagin, N. A. Catal.
Commun. 2016, 79, 17. Mino, T.; Shindo, H.; Kaneda, T.;
Koizumi, T.; Kasashima, Y.; Sakamoto, M.; Fujita, T. Tet-
rahedron Lett. 2009, 50, 5358
[
36,39]
times,
low catalyst loading,
[4u1s]e of open
[
28]
atmosphere and the absence of additives.
Finally, the use of infrared irradiation as the energy
source promotes the Mizoroki-Heck and Suzu-
ki-Miyaura cross-coupling reactions in an efficient way
in lower reaction times, compared to experiments per-
formed using conductive heating.
[16] (a) Hashmi, A.S.K.; Lothschütz, C.; Böhling, C.; Rominger,
F. Organometallics 2011, 30, 2411; (b) Zeiler, A.; Rudolph,
M.; Rominger, F.; Hashmi, A.S. K Chem. Eur. J. 2015, 21,
11065; (c) Tšupova, S.; Rudolph, M.; Rominger, F.; Hash-
mi, A.S.K. Adv. Synth. Catal. 2016, 358, 3999; (d) Riedel,
D.; Wurm, T.; Graf, K.; Rudolph, M.; Rominger, F.; Hashmi
A.S.K. Adv. Synth. Catal. 2015, 357, 1515; (e) Hashmi,
A.S.K.; Lothschtz, C.; Bçhling, C.; Hengst, T.; Hubbert, C.;
Rominger, F. Adv. Synth. Catal. 2010, 352, 3001.
Conclusions
Arylhydrazones 1-2 containing the benzothiazole
moiety are an efficient ligand in the palladium-catalyzed
Mizoroki-Heck and Suzuki-Miyaura cross-coupling
reactions under infrared irradiation. The stability of the
[
17] Kappe, C.O.; Dallinger, D.; Murphree, S.S. Practical Mi-
crowave Synthesis for Organic Chemists Strategies, Instru-
ments and Protocols, Wiley-VCH, Weinheim, 2009.
[
2
Pd(OAc) /arylhydrazone] system to both air and mois-
ture, avoids the use of inert conditions and facilitates all
the manipulation processes in open atmosphere. There-
fore, we evidence that infrared irradiation is an efficient,
economical, and accessible alternative source of energy
to assist Mizoroki-Heck and Suzuki-Miyaura
cross-coupling reactions.
[
18] Nowak, F.M. Sonochemistry: Theory, Reactions, Syntheses,
and Applications, Nova Science Publishers New York,
2
011.
19] Escobedo, R.; Miranda, R.; Martínez, J. Int. J. Mol. Sci.
016, 17, 453.
[
[
2
20] (a) Ortega-Jiménez, F.; Domínguez-Villa, F.X.;
Rosas-Sánchez, A.; Penieres-Carrillo, J.G.; López-Cortés,
J.G.; Ortega-Alfaro, M.C. Appl. Organomet. Chem. 2015,
Acknowledgement
2
9, 556; (b) Ortega-Jiménez, F.; Penieres-Carrillo, J.G.;
The authors would like to acknowledge the technical
assistance provided by Luis Velasco and Javier Pérez.
The authors also thank DGAPA-PAPIIT 215116 and
FES Cuautitlán-UNAM PIAPIC14 grants.
Lagunas-Rivera, S.; López-Cortés, J.G.; Álvarez-Toledano,
C.; Ortega-Alfaro, M.C. RSC Adv.2015, 5, 80911.
[
21] Balam-Villarreal, J.A.; Sandoval-Chávez, C.I.; Orte-
ga-Jiménez. F.; Toscano, R.A.; Carreón-Castro, M.P.;
López-Cortés, J.G.; Ortega-Alfaro, M.C. J. Organomet.
Chem. 2016, 818, 7.
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Entry for t hh e Table of Contents
Page No.
Arylhydrazon ee s derivatives contain-
ing the benz oo thiazole moiety, efficient
ligands in tt he palladium-catalyzed
Mizoro-ki-He cc k and Suzuki-Miyaura
cross-coupli nn g reactions under IR
irradiation.
Fernando
Ortega-Jiménez*
José
A simple arylhydrazone 1 and 2 that containing a benzothiazole moiety are used as effi-
Guillermo Penieres-Carrillo, José Gua-
dalupe López -- Cortés, M. Carmen Orte-
ga-Alfaro and SS elene Lagunas-Rivera.
cient ligand in the Mizoroki-Heck and Suzuki-Miyaura cross-coupling to the palladi-
um-catalyzed under infrared irradiation
ported.
aa s an alternative source of energy is herein re-
This article is protected by copyright. All rights reserved.