D
K. Ping et al.
Letter
Synlett
ingly, catalyst TAL-7-900 performed similarly to TAL-1-900
in the oxidation of toluene (Scheme 2; isolated yield 38% vs.
34%); however, the yield from the oxidation of ethylben-
zene was significantly less (28% vs. 44%).
References and Notes
(1) Yuan, S.; Feng, L.; Wang, K.; Pang, J.; Bosch, M.; Lollar, C.; Sun, Y.;
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We have previously shown by microwave plasma atom-
ic-emission spectroscopy that the total amount of iron in
TAL-1-900 (0.896 ± 0.006 wt%) differs from that in TAL-7-
900 (3.603 ± 0.035 wt%).11 Despite the fact that TAL-7-900
contains about four times as much iron as TAL-1-900, we
found that TAL-1-900 performed as well as or slightly better
than TAL-7-900 in oxidative transformations (Reactions A
and B; Table 1 and Scheme 2). Notably, whereas the two
benzimidazole-based organic linkers used to prepare TAL-
1- and TAL-7-derived catalysts both contain electron-do-
nating groups (OH and OMe, respectively), only the unpro-
tected catechol had the propensity to form bis- and triscat-
echolato complexes with iron.25 Hence, the precise nature
of the iron complexes formed at the surface of the catalyst
material following carbonization might contribute to the
overall catalytic performance of our heterogeneous cata-
lysts. In practice, one would seek to employ additional po-
rous carbon supports,26 which might increase the accessible
specific surface area of the final catalyst material.
In summary, we have shown that iron-based TAL-1-900
is a reliable catalyst for the oxidation of alkylarenes to the
corresponding carboxylic acids or ketones. Because the to-
tal iron content in this heterogeneous catalyst is very low
(≤1%), its performance as a catalyst is promising. The long-
term advantages of using metal-doped carbonized materi-
als as catalysts for organic transformations include their re-
cyclability, low metal leaching, and no requirement for ad-
ditional ligands.
(9) Kong, D.; Gao, Y.; Xiao, Z.; Xu, X.; Li, X.; Zhi, L. Adv. Mater. ; DOI:
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(10) For leading references on the use of MOF-derived carbonized
materials in ORR/OER, see: (a) Zhao, S.; Yin, H.; Du, L.; He, L.;
Zhao, K.; Chang, L.; Yin, G.; Zhao, H.; Liu, S.; Tang, Z. ACS Nano
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Wang, X. Nat. Energy 2016, 1, 15006. (c) Li, J.; Chen, M.; Cullen,
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(11) Ping, K.; Braschinsky, A.; Alam, M.; Bhadoria, R.; Mihkli, V.;
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Sammelselg, V.; Tammeveski, K.; Kongi, N.; Starkov, P. ChemRxiv
2019; preprint; DOI: 10.26434/chemrxiv.7687358
(12) For recent references on the use of MOF-derived carbonized
materials in organic transformations, see: (a) Jagadeesh, R. V.;
Murugesan, K.; Alshammari, A. S.; Neumann, H.; Pohl, M.-M.;
Radnik, J.; Beller, M. Science 2017, 358, 326–332. (b) Murugesan,
K.; Beller, M.; Jagadeesh, R. V. Angew. Chem. Int. Ed. 2019, 58,
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1808341. (d) Xie, F.; Lu, G.-P.; Xie, R.; Chen, Q.-H.; Jiang, H.-F.;
Zhang, M. ACS Catal. 2019, 9, 2718. (e) Wu, Y.; Chen, Z.; Cheong,
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Funding Information
Funding Information: Tallinna Tehnikaülikool, (Grant/Award Number:
B62) Eesti Teadusagentuur, (Grant/Award Number: IUT19-9, IUT34–
14, PSG250, and PUT1290).
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Acknowledgment
(15) Masa, J.; Xia, W.; Muhler, M.; Schuhmann, W. Angew. Chem. Int.
Ed. 2015, 54, 10102.
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2016, 2, e1501122.
This research was funded by Estonian Research Council Grant
PUT1290 and TalTech Young Investigator Grant B62 (both to P.S.). K.P.
acknowledges the Estonian Smart Specialization Ph.D. Fellowship. The
BET measurements were funded by Institutional Research Grant
IUT34–14. The HRMS facilities are funded by Institutional Research
Funding IUT19–9. N.K. is funded by Estonian Research Council Grant
PSG250.
(18) Zhang, L.; Xiao, J.; Wang, H.; Shao, M. ACS Catal. 2017, 7, 7855.
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Supporting Information
Supporting information for this article is available online at
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A mixture of mesitylene (100 mg, 0.832 mmol, 1.0 equiv), 70%
aq TBHP (2.05 mL, 14.98 mmol, 18.0 equiv), and TAL-1–900 (4.2
© 2019. Thieme. All rights reserved. — Synlett 2019, 30, A–E