W(CO)5-amine catalyzed exo- and endo-selective cyclizations of ω-alkynyl silyl enol ethers: A highly useful method for the construction of polycyclic compounds

Organic Letters

Volumn 4, Issue 15, 2002, Pages 2569-2571

  Kusama, Hiroyuki ^a   Yamabe, Hokuto ^a   Iwasawa, Nobuharu ^a  

^a TOKYO INSTITUTE OF TECHNOLOGY   (Japan)

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Indexed keywords

EID: 0013263922     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol026202c     Document Type: Article

References (19)

1. 5(L) in synthesis (M = Cr, Mo, W), see; (a) Dötz, K. H.; Sturm, W. Organometallics 1987, 6, 1424.
2. (b) McDonald, F. E.; Chatterjee, A. K. Tetrahedron Lett. 1997, 38, 7687.
3. (c) Cutchins, W. W.; McDonald, F. E. Org. Lett. 2002, 4, 749.
4. (c) Painter, J. E.; Quayle, P. Tetrahedron Lett. 1995, 36, 8089.
5. (e) Ohe, K.; Yokoi, T.; Miki, K.; Nishino, F.; Uemura, S. J. Am. Chem. Soc. 2002, 124, 526.
6. (a) Iwasawa, N.; Maeyama, K.; Kusama, H. Org. Lett. 2001, 3, 3871.
7. (b) Maeyama, K.; Iwasawa, N. J. Am. Chem. Soc. 1998, 120, 1928. See also:
8. (c) Maeyama, K.; Iwasawa, N. J. Org. Chem., 1999, 64, 1344.
9. (d) Iwasawa, N.; Shido, M.; Kusama, H. J. Am. Chem. Soc. 2001, 123, 5814.
10. (e) Miura, T.; Iwasawa, N. J. Am. Chem. Soc. 2002, 124, 518.
11. For recent examples of nucleophilic endo-selective cyclization onto alkynes, see: (a) Kim, K.; Okamoto, S.; Sato, F. Org. Lett. 2001, 3, 67.
12. (b) Imamura, K.; Yoshikawa, E.; Gevorgyan, V.; Yamamoto, Y. Tetrahedron Lett. 1999, 40, 4081.
13. Imamura, K.; Yoshikawa, E.; Gevorgyan, V.; Yamamoto, Y. J. Am. Chem. Soc. 1998, 120, 5339.
14. No reaction occurred with amines such as DBU and pyridine, probably because of their strong coordination to tungsten.
15. 5(amine) complexes, see; Kirtley, S. W. Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds; Pergamon Press: Oxford, UK, 1982; Vol. 3, p 1079.
16. (6) We are currently pursuing research to clarify the effect of the amines on the exo vs. endo selectivity.
17. The tetracyclic ketals 6b and 6e were produced as follows: nucleophilic attack of the ester carbonyl on the silyloxonium moiety results in the tricyclic intermediates F. Then the alkenyl tungsten attacks the oxonium moiety to give carbene intermediates, which finally give 6 by a 1,2-hydrogen shift. (Matrix presented)
18. Deprotonation of the intermediate 11 would violate Bredt's rule.
19. The allene 13 is thought to be produced as shown below. (Matrix presented)