Inorganic Chemistry
Communication
presence of K CO as a base using our previously optimized
and represent a new family of catalysts containing an unusual
1,3,5,7-tetraza-2,6-dipalladocane frame.
2
3
4
d,e
conditions.
A high yield of the corresponding cross-
coupling product was obtained when the reaction proceeded
at 20−40 °C for 15−30 min using isoxazole complexes
ASSOCIATED CONTENT
sı Supporting Information
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1
2
Pd Cl (L -H) and Pd Cl (L -H) (Table 1, entries 1, 2, 4 and
*
2
2
2
2
2
2
5
), whereas at 100 °C the reaction time decreased to 1−2 min
for isoxazole complexes (entries 3 and 6) and 20 min for
isothiazole complexes (entries 12 and 15). It is noteworthy
that under the catalysis by new complexes we did not observe
the formation of Pd black even after full completion of the
reaction (controlled by optical microscopy). It is possible that
only a “homeopathic” part of the initial palladium complex
participates in the catalytic cycle, and it is logical to try to
reduce its amount. Indeed, when the amount of palladium was
Details of synthesis, X-ray diffraction studies, and
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2
decreased to 0.01−0.001 mol % Pd [complex Pd Cl (L -H) ],
a quantitative amount of cross-coupling product was obtained
2
2
2
after 4−5 min at 100 °C with TON up to 100 000 and TOF up
−
1
to 1 200 000 h (entries 7 and 8). When using aryl iodides in
the reaction, the amount of catalyst can be reduced even to
Corresponding Authors
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0
.0001 mol % (1 ppm). Under these conditions, the reaction
proceeded quantitatively in 5 min with high TON of 1 000 000
and TOF of 12 000 000 h− (entry 9). It is important to note
that in the presence of Na PdCl (without N-ligands) reaction
Alexey V. Kletskov − Chemical Department, M.V. Lomonosov
Moscow State University, Moscow 119991, Russian Federation;
Institute of Physical Organic Chemistry, National Academy of
Sciences of Belarus, Minsk 220072, Belarus; Peoples’ Friendship
Nikolay A. Bumagin − Chemical Department, M.V. Lomonosov
1
2
4
mixtures quickly changed to a dark color and Pd-black
formation was observed (entries 16 and 17).
The reaction of different aryl bromides 11a−d with electron-
deficient arylboronic acids 12a−f in the presence of 0.01 mol
Pd led to the desired biaryls in high yields (93−98%, Table
S, entries 1−7, SI). Moreover, sterically hindered 2-
formylphenyboronic acid 12d underwent coupling with 11d
to produce the bifunctional product 13dd in 95% yield (Table
Vladimir I. Potkin − Institute of Physical Organic Chemistry,
1
S, entry 5). These results indicate that N-(pyrimidin-2-yl)-
1
,2-azole-3-carboxamide complexes Pd Cl (L -H) −
2
2
2
4
Pd Cl (L -H) are very effective catalysts for the Suzuki
2
2
2
Authors
Sergey K. Petkevich − Institute of Physical Organic Chemistry,
National Academy of Sciences of Belarus, Minsk 220072,
Evgenij A. Dikusar − Institute of Physical Organic Chemistry,
National Academy of Sciences of Belarus, Minsk 220072,
To demonstrate the potential utility of the new catalytic
system, the gram-scale synthesis of the key intermediate in the
synthesis of Boscalid fungicide was performed (Scheme 2,
1
0
compound 16), as well as one-step synthesis of 2′,4′-
difluoro-4-hydroxy-[1,1′-biphenyl]-3-carboxylic acid (diflu-
nisal) 19, a nonsteroidal anti-inflammatory drug (NSAID)
Alexander S. Lyakhov − Research Institute for Physical
Chemical Problems of Belarusian State University, Minsk
1
1
(
Scheme 3).
We also evaluated the catalytic activity of Pd Cl (L-H)
2
2
2
2
Ludmila S. Ivashkevich − Research Institute for Physical
Chemical Problems of Belarusian State University, Minsk
shira reaction (Tables 2, 3, 3S, and 4S). The practical
applicability was demonstrated by the scaled-up synthesis of
the UV-sunscreen agent octinoxate (Scheme 4) and 2-
2
Iryna A. Kolesnik − Institute of Physical Organic Chemistry,
National Academy of Sciences of Belarus, Minsk 220072,
Belarus
(
phenylethynyl)aniline 28 (Scheme 5), as 2-alkynyl anilines,
12
key intermediates in the indole synthesis.
It should be emphasized that the reactions of water-insoluble
reagents easily proceed in water in the presence of trace
amounts (1 mol %) of Bu NBr as the phase transfer catalyst
4
Notes
(Tables 2 and 3; Schemes 2, 4, and 5). No byproducts were
The authors declare no competing financial interest.
detected for the catalysts, and cross-coupling products were
isolated without the application of chromatography.
For the first time, cyclic phosphine-free “head to tail” N,N,N
pincer-like Pd(II) complexes on N-(pyrimidin-2-yl)-1,2-azole-
ACKNOWLEDGMENTS
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The publication has been prepared with the support of the
Russian Foundation for Basic Research (Grant 18-58-00013-
Bel_a, 20-58-00005-Bel_a), the Belarusian Republican Foun-
dation for Fundamental Research (Grant X18P-010, X20P-
017). The publication has been prepared with the support of
the “RUDN University Program 5-100”.
3
-carboxamide frameworks with deprotonated amide groups
were obtained and used as high TON and TOF catalysts for
C−C cross-coupling reactions under green conditions. The
obtained complexes conceptually mimic the coordination
centers of much less accessible N,N,N-pincer-type complexes
D
Inorg. Chem. XXXX, XXX, XXX−XXX