Synlett 2016; 27(04): 581-585
DOI: 10.1055/s-0035-1561677
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© Georg Thieme Verlag Stuttgart · New York

Study of Stereocontrolling Elements in Chiral Phosphoric Acid Catalyzed Addition Reaction of Vinylindoles with Azlactones

Kyohei Kanomata
a   Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
,
Masahiro Terada*
a   Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
b   Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan   eMail: mterada@m.tohoku.ac.jp
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Publikationsverlauf

Received: 21. Oktober 2015

Accepted after revision: 19. Januar 2016

Publikationsdatum:
04. Februar 2016 (online)


Abstract

DFT studies were carried out to clarify the reaction mechanism and the stereocontrolling elements in the addition reaction of vinylindoles with azlactones catalyzed by a chiral phosphoric acid. The results suggest that the reaction proceeds via a six-membered transition state that is composed of the vinyl group of vinylindole and the enol moiety of azlactone.

Supporting Information

 
  • References

  • 1 Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Kyoto 615-8510, Japan.
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  • 13 A mechanistic study of chiral phosphoric acid catalyzed reaction of vinyl ethers with azlactones11a was carried out. Kanomata, K.; Nagasawa, Y.; Shibata, Y.; Egawa, F.; Yamanaka, M.; Terada, M. manuscript in preparation.
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  • 16 Relative and absolute configurations were determined by X-ray crystallographic analysis after derivatization of the product. See ref. 5 for details.
  • 17 See the Supporting Information for the structures and energies of TSa-rs and TSa-sr, leading to the formation of minor anti-5a.
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  • 23 These substituent effects are in sharp contrast to those in the reaction of vinyl ethers with azlactones. In the reaction of vinyl ethers with azlactones, the 3,5-dimethoxyphenyl group was the optimal substituent. See refs. 5 and 11a for details. See also: Lu G, Birman VB. Org. Lett. 2011; 13: 356
  • 24 See the Supporting Information for the structures of TSb-ss and TSb-rr.