10.1002/adsc.201900686
Advanced Synthesis & Catalysis
the catalyst was collected by centrifugation. It was
additionally washed twice with water (12 mL) and once
again with ethanol (12 mL). The isolated catalyst was used
in the next cycle.
going improvement of diverse catalysts for numerous
practical applications gives access to sustainable
development.
Experimental Section
Acknowledgments
Pd/C Catalyst preparation
This work was supported by the Russian Science Foundation
(RSF Grant 19-13-00460).
For the synthesis of Pd/C catalysts a freshly made
Pd2dba3·CHCl3
precursor
was
prepared
via
recrystallization and its quality was controlled by 1H
NMR.[23] The 1% Pd/Vulcan, Pd/MWCNT and Pd/graphite
catalysts were obtained following the “mix-and-stir”
approach, which was reported recently.[14] Palladium
content was 1% by weight.
References
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In typical procedure, Pd2dba3·CHCl3 (25.0 mg), Vulcan
carbon black (500 mg), CHCl3 (25 mL), and a magnetic
stirrer were loaded into a screw-capped reaction vessel and
placed in an oil bath at 80 °C under stirring. After the
dissolution of Pd2dba3, a dark red solution was formed, and
stirring was performed until the red color of the solution
disappears. The Pd/C catalyst was separated from the
solution by filtration or centrifugation, washed with
acetone (30 mL) to remove free dba, and dried under
reduced pressure (0.01 bar, 50 °C). A detailed step-by-step
procedure is provided in the dedicated video.[24]
Experimental Procedure for the
Hydrodebenzylation
1 mmol Scale
In typical case, an aliquot of 5 mL of reductant solution
and a magnetic stirring bar were placed into 15 mL
reaction vessel. Then, a portion of substrate (1 mmol) was
added. The reaction mixture was placed into a heating
block. After a short period of time, a portion of the catalyst
wais added to the heated reaction mixture. The conversion
was monitored by 1H NMR spectroscopy. After the
reaction, the mixture was cooled to room temperature and
filtered through PTFE membrane filter. The filter was
additionally washed with ethanol; the filtrates were
combined, evaporated and the crude product was purified
by flash column chromatography on a silica gel column to
obtain the desired product.
Experimental Procedure for the Multi-Gram Scale
Hydrodebenzylation (5 or 10 mmol scale)
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J. Gao, C.-J. Li, Angew. Chem., Int. Ed. 2018, 57,
16520-16524; Angew. Chem. 2018, 130, 16758-16762;
c) A. Grünwald, N. Orth, A. Scheurer, F. W.
Heinemann, A. Pöthig, D. Munz, Angew. Chem., Int.
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16463-16467; d) S. Mitchell, E. Vorobyeva, J. Pérez-
Ramírez, Angew. Chem., Int. Ed. 2018, 57, 15316-
15329; Angew. Chem. 2018, 130, 15538-15552.
In typical case, a magnetic stirring bar, a portion of a
substrate (X mmol) and 5X mL of reductant solution were
placed in a three-necked round-bottom flask. The ratio of
formic acid, KOH and ethanol was equal to that for 1
mmol scale hydrodebenzylation reaction. The reaction
mixture was heated at reflux conditions. After a short
period of time, a portion of the catalyst was added to the
heated reaction mixture. The conversion was monitored by
1H NMR spectroscopy. After the reaction, the mixture was
cooled to room temperature and filtered through a pad of
Celite®. The pad was additionally washed with ethanol; the
filtrates were combined, evaporated and crude product was
purified by flash column chromatography on a silica gel
column to obtain the desired product.
[3] a) Q. Wang, N. Tsumori, M. Kitta, Q. Xu, ACS Catal.
2018, 8, 12041-12045; b) X. Chen, Y. Zheng, F. Huang,
Y. Xiao, G. Cai, Y. Zhang, Y. Zheng, L. Jiang, ACS
Catal. 2018, 8, 11016-11028; c) Y. Chai, S. Liu, Z.-J.
Zhao, J. Gong, W. Dai, G. Wu, N. Guan, L. Li, ACS
Catal. 2018, 8, 8578-8589.
Recycling of the Pd/Vulcan catalyst
A 15 mL reaction vessel was loaded with 6 mmol of
HCO2H, 5 mmol of KOH, 5 mL of ethanol, substrate
(1 mmol for 1a; 0.5 mmol for 2b) and a magnetic stirring
bar. The vessel was placed in heating block with
temperature set to 40 °C. A sample of the Pd/Vulcan
catalyst (31.8 mg, 3 µmol of palladium) was added to the
heated reaction mixture and it was stirred at 40 °C for
[4] a) P. Slavík, D. W. Kurka, D. K. Smith, Chem. Sci.
2018, 9, 8673-8681; b) V. M. Chernyshev, O. V.
Khazipov, M. A. Shevchenko, A. Y. Chernenko, A. V.
Astakhov, D. B. Eremin, D. V. Pasyukov, A. S. Kashin,
V. P. Ananikov, Chem. Sci. 2018, 9, 5564-5577; c) L.-
1
60 min. After a probe for H NMR analysis was taken, the
reaction mixture was quenched with ethanol (7 mL) and
7
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