Communication
served.[17] The strong Lewis acid zinc trifluoromethanesulfonate
[Zn(OTf)2] exhibited poor catalytic performance. To facilitate
Zn(OTf)2 catalysis, the reaction was performed under neat con-
ditions (Scheme 3, b). Whereas the combined use of
Zn4(OCOCF3)6O (1) and DMAP (5) provided the product in 99 %
yield without undesired polymerization, Zn(OTf)2 promoted
only polymerization, presumably initiated by the conjugate ad-
dition of the alcohols,[18,19] which suggested that hard zinc alk-
oxide generation was crucial for highly chemoselective trans-
esterification.
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M. Hatano, K. Ishihara, Chem. Commun. 2013, 49, 1983.
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Conclusion
In summary, we developed a highly chemoselective trans-
esterification of acrylate derivatives through hard zinc alkoxide
generation. High functional group compatibility, including the
hydrophilic ether functionality, clearly demonstrated the utility
of the present zinc catalysis for the synthesis of functionalized
monomers. Further application of the present catalysis for the
preparation of functionalized monomers with novel features
and functional evaluation of their polymers are underway.
[10] a) L. G. Hess, C. W. Va, U. S. patent 3227628 A, 1966; b) J. W. Breitenbach,
H. Axmann, Polymerization Kinetics and Technology (Ed.: N. A. J. Platzer),
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[11] Inferior results were observed at elevated temperatures by using toluene
as the solvent.
Acknowledgments
[12] Co4(OCOCF3)6O afforded a trace amount of product 4aa.
[13] 4 Å Molecular sieves were used to remove the methanol generated.
[14] Although product 4aa was observed in high yield by using a slight ex-
cess amount of 2a (Table 1, entries 11 and 12), we used neat conditions
to evaluate the substrate scope because both methyl methacrylate (2a)
and methyl acrylate (2b) are inexpensive. 2a: $18/500 mL, 2b: $20/
500 mL from TCI America as of May 2016.
[15] We also performed the reaction without Zn(OCOCF3)2 (1). In these cases,
no reaction was observed by using DMAP or trifluoroacetic acid as a
catalyst.
This work was financially supported by the Ministry of Educa-
tion, Culture, Sports, Science and Technology (MEXT), Scientific
Research on Innovative Area 2707 Middle Molecular Strategy
and Platform for Drug Discovery, Informatics, and Structural Life
Science from the. The authors thank the research group of Prof.
Hiroshi Suemune at Kyushu University for the use of a polarime-
ter.
[16] Along with tris(acrylate) product 9bf, bis(acrylate) product was obtained
in 34 % yield.
[17] Zn4(OCOCF3)6O (1) would be generated from Zn(OCOCF3)2 under heat-
ing conditions, which would allow for chemoselective transesterification,
see: Y. Hayashi, T. Ohshima, Y. Fujii, Y. Matsushima, K. Mashima, Catal. Sci.
Technol. 2011, 1, 230.
Keywords: Chemoselectivity · Transesterification ·
Acrylates · Alkoxides · Zinc
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Received: June 16, 2016
Published Online: ■
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