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mmol), and 1-ethyl-3-(3-dimethylaminopropyl)carbodiamide
Acknowledgements
hydrochloride (EDC$HCl, 10 mmol) in THF (50 mL) was stir-
ꢀ
red overnight at 25 C. The resulting mixture was ltered, and
This research was nancially supported by National Science
Foundation of China (21462031), Program for Young Talents of
Science and Technology in Universities of Inner Mongolia
Autonomous Region (NJYT-17-A22).
the ltrate was evaporated in vacuo. The residue was puried by
ash column chromatography (silica gel, ethyl ether/petroleum
ether ¼ 1 : 3–1 : 10 as eluent) to afford a corresponding (hetero)
aryl esters.
Notes and references
General procedure for K2CO3-catalyzed transesterication
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In a typical reaction, aryl ester (0.10 mmol), phenol (0.17 mmol),
catalyst (0.01 mmol or 0.02 mmol), and the solvent 1,4-dioxane
(2.0 mL) were charged in a 25 mL oven dried reaction tube.
Reaction was carried out 60 ꢀC or 120 ꢀC for 48 h in an oil bath
under air condition. Aer being cooled to room temperature,
the reaction solution was evaporated in vacuo. The residue was
puried by ash column chromatography (silica gel, ethyl
acetate/petroleum ether ¼ 1 : 5–1 : 15 as an eluent) to afford the
desired product 3. All the products were also conrmed by
comparing the 1H NMR and 13C NMR data with authentic
samples.
3 (a) M. Kumar, S. Bagchi and A. Sharma, New J. Chem., 2015,
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10 gram-scale synthesis of 3aa
4 Some papers on Lewis acids as catalysts for
transesterications: (a) D. P. Sheng and I. O. Kady, Appl.
Catal., A, 2009, 365, 149; (b) J. W. J. Bosco and A. K. Saikia,
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In a 10 gram-scale reaction, pyridin-2-yl 2-methylbenzoate 1a
(10 g, 47.0 mmol), phenol 2a (7.51 g, 79.9 mmol), K2CO3 (0.65 g,
4.7 mmol), and the solvent (150 mL) were charged in a 250 mL
ꢀ
ovendried round ask. Reaction was carried out 60 C for 48 h
in an oil bath under air condition. Aer being cooled to room
temperature, the reaction solution was evaporated in vacuo. The
residue was puried by ash column chromatography (silica
gel, ethyl acetate/petroleum ether ¼ 1 : 5–1 : 15 as an eluent) to
afford the desired product 3aa (9.85 g, 99% yield).
´
V. Sridharan, M. Ruiz and J. C. Menendez, Synthesis, 2010,
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Conclusions
In conclusion, we have disclosed an alkali metal catalyzed
transesterication of various heteroaryl esters or aryl esters with
phenols. The chemistry proceeds under mild conditions and
enables the direct synthesis of a wide array of useful aryl esters,
with high tunability in both the ester and phenol. In general,
the pyridyloxy and electron-decient phenoxy of the aryl esters
are easily exchanged by electron-rich phenols. But some exam-
ples could not be explained by a simple nucleophilic substitu-
tion reaction process. Being insoluble in many of the solvent
systems, K2CO3 offers the advantages of ease of recovery from
the reaction medium by mere ltration and reuse of the
recovered material. This methodology meets the requirement of
the ideal transesterication, which is to achieve quantitative
yield with the reactants in a ratio near 1 : 1 by use of mild,
recyclable catalysts without requiring any technology to remove
any coproduct. Detailed mechanistic studies by computational
and experimental methods are underway.
6 Some papers on NHCs as catalysts for transesterications:
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7 C. Yu, H. Huang, X. Li, Y. Zhang and W. Wang, J. Am. Chem.
Soc., 2016, 138, 6956–6959.
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Z. J. Shi, Angew. Chem., Int. Ed., 2010, 49, 4566; (b) Z. Chen,
H. Zeng, S. A. Girard, F. Wang, N. Chen and C. J. Li, Angew.
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A. Dom&nguez-Huerta, Z. Hearne, Z. Chen and C. J. Li, ACS
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Conflicts of interest
10 (a) H. Xu, K. Muto, J. Yamaguchi, C. Zhao, K. Itami and
D. G. Musaev, J. Am. Chem. Soc., 2014, 136, 14834–14844;
There are no conicts to declare.
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RSC Adv., 2018, 8, 25168–25176 | 25175