A novel reaction for annulation onto α,β-unsaturated ketones: W(CO)5·L promoted exo-and endo-selective cyclizations of ω-acetylenic silyl enol ethers prepared by 1,4-addition of propargyl malonate to enones

Organic Letters

Volumn 3, Issue 24, 2001, Pages 3871-3873

  Iwasawa, Nobuharu ^a   Maeyama, Katsuya ^b,c   Kusama, Hiroyuki ^a  

^a TOKYO INSTITUTE OF TECHNOLOGY   (Japan)

^b UNIVERSITY OF TOKYO   (Japan)

^c TOKYO UNIVERSITY OF AGRICULTURE AND TECHNOLOGY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001165674     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol016718g     Document Type: Article

References (21)

1. Only a few papers on such reactions have been reported. See for examples: (a) Negishi, E.; Tour, J. M. Tetrahedron Lett. 1986, 27, 4869.
2. (b) Snider, B. B.; Merritt, J. E.; Dombroski, M. A.; Buckman, B. O. J. Org. Chem. 1991, 56, 5544.
3. (c) Lemaire-Audoire, S.; Savignac, M.; Dupuis, C., Genêt, J.-P. Tetrahedron Lett. 1996, 37, 2003.
4. (d) Kim, K.; Okamoto, S.; Sato, F. Org. Lett. 2001, 3, 67.
5. Maeyama, K.; Iwasawa, N. J. Am. Chem. Soc. 1998, 120, 1928.
6. See also: (a) Maeyama, K.; Iwasawa, N. J. Org. Chem. 1999, 64, 1344.
7. (b) Iwasawa, N.; Shido, M.; Maeyama, K.; Kusama, H. J. Am. Chem. Soc. 2000, 122, 10226.
8. (c) Iwasawa, N.; Shido, M.; Kusama, H. J. Am. Chem. Soc. 2001, 123, 5814.
9. There are only a few methods for the endo-selective intramolecular nucleophilic addition of carbon nucleophiles to alkynes. For examples, see: (a) McDonald, F. E.; Olson, T. C. Tetrahedron Lett. 1997, 38, 7691.
10. (b) Imamura, K.; Yoshikawa, E.; Gevorgyan, V.; Yamamoto, Y. J. Am. Chem. Soc. 1998, 120, 5339.
11. (c) Imamura, K.; Yoshikawa, E.; Gevorgyan, V.; Yamamoto, Y. Tetrahedron Lett. 1999, 40, 4081. See also: McDonald, F. E. Chem. Eur. J. 1999, 5, 3103.
12. (c) Imamura, K.; Yoshikawa, E.; Gevorgyan, V.; Yamamoto, Y. Tetrahedron Lett. 1999, 40, 4081. See also: McDonald, F. E. Chem. Eur. J. 1999, 5, 3103.
13. It should be noted that TBSOTf does not silylate Na propargylmalonate but works as an effective activator of cyclohexenone.
14. 2O, as otherwise, partial isomerization of the double bond occurs to give α,β-unsaturated ketones.
15. Rücker, C. Chem. Rev. 1995, 95, 1009.
16. It is necessary to control the irradiation time when the reaction is run under conditions B. Longer irradiation results in a decrease in yield of the endo-cyclized product.
17. 6 employed is not the cause for this difference of the exo vs endo selectivity.
18. Under conditions A, exo-cyclized products 2a-2e were obtained as a single isomer, whose stereochemistry (ring junction) was confirmed to be cis by NOE experiments. 2f was obtained as a 10:1 isomeric mixture of two exo-cyclized products, accompanied by a small amount of endo-cyclized product 3f. (10) Under conditions B, all endo-cyclized products 3a-3f were obtained as a single isomer. The stereochemistry (ring junction) of 3a-3d was confirmed to be cis by NOE experiments. That of 3e and 3f was tentatively assigned as trans, because we could not observe NOE between protons on the ring junction. We are currently trying to confirm the stereochemistry of these two products.
19. 2. By this modified procedure, the desired substrates 4 were obtained in good vields.
20. See the Supporting Information for the details of the method for the determination of the stereochemistry of the starting materials and the products.
21. 6 in toluene in the presence of MeOH (conditions C) gave slightly better results than the direct irradiation method (conditions B).