Thermal promotion of the cobalt catalyzed intramolecular Pauson-Khand reaction - An alternative experimental protocol for cyclopentenone synthesis

Tetrahedron Letters

Volumn 39, Issue 42, 1998, Pages 7637-7640

  Belanger, David B ^a   O'Mahony, Donogh J R ^a   Livinghouse, Tom ^a  

^a MONTANA STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

COBALT; CYCLOPENTENONE;

ARTICLE; CATALYSIS; CHELATION; CYCLIZATION; MOLECULAR INTERACTION; STRUCTURE ANALYSIS;

EID: 0032532517     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)01693-1     Document Type: Article

References (17)

1. 1. Recipient of a Japan Society for the Promotion of Science Fellowship, 1997.
2. 2. Geis, O.; Schmalz, H. G. Angew. Chem. Int. Ed. Engl. 1998, 37, 911-914.
3. 3. (a) Khand, I. U.; Knox, G. R.; Pauson, P. L.; Watts, W. E.; Foreman, M. I. J. Chem. Soc. Perkin Trans. I 1973, 977-981.
4. (b) The formation of enones was first described, though poorly, in a communication: Khand, I. U.; Knox, G. R.; Pauson, P. L. J. Chem. Soc. Chem. Commun. 1971, 36.
5. 4. Kim, J. W.; Chung, Y. K. Synthesis 1998, 142-144.
6. 5. (a) Hicks, F. A.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 11688-11689.
7. (b) Hicks, F. A.; Kablaoui, N. M.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 9450-9651.
8. 6. Koga, Y. ; Kobayashi, T. ; Narasaka, K. Chem. Lett. 1998, 249-250.
9. 7. (a) Kondo, T.; Suzuki, N.; Okada, T.; Mitsudo, T. J. Am. Chem. Soc. 1997, 119, 6187-6188.
10. (b) Chatani, N.; Morimoto, T.; Fukumoto, Y.; Murai, S. J. Am. Chem. Soc. 1998, 120, 5335-5336.
11. 8. Jeong, N.; Hwang, S. H.; Lee, Y. W.; Lim, J. S. J. Am. Chem. Soc. 1997, 119, 10549-10550.
12. 9. Pagenkopf, B. L.; Livinghouse, T. J. Am. Chem. Soc. 1996, 118, 2285-2286
13. 10. Jeong has reported a catalytic thermally promoted protocol at higher temperatures (120 °C) and pressures (4-5 atm) in the presence of phosphite coligands. For lower turnovers in other intramolecular cases see ref. 6 therein: Jeong, N.; Hwang, S. H.; Lee, Y. J. Am. Chem. Soc. 1994, 116, 3159-3160. An intermolecular cyclization with highly strained alkenes was also described in the initial work: see ref. 3a. Higher temperatures (150 °C) and pressures (310-360 atm) were also described for a catalytic preparation of 2-pentyl-cyclopentenone: Rautenstrauch, V.; Mégard, P.; Conesa, J. Küster, W. Angew. Chem. Int. Ed. Engl. 1990, 29, 1413-1416.
14. 10. Jeong has reported a catalytic thermally promoted protocol at higher temperatures (120 °C) and pressures (4-5 atm) in the presence of phosphite coligands. For lower turnovers in other intramolecular cases see ref. 6 therein: Jeong, N.; Hwang, S. H.; Lee, Y. J. Am. Chem. Soc. 1994, 116, 3159-3160. An intermolecular cyclization with highly strained alkenes was also described in the initial work: see ref. 3a. Higher temperatures (150 °C) and pressures (310-360 atm) were also described for a catalytic preparation of 2-pentyl-cyclopentenone: Rautenstrauch, V.; Mégard, P.; Conesa, J. Küster, W. Angew. Chem. Int. Ed. Engl. 1990, 29, 1413-1416.
15. 11. The narrow thermal window may be a result of decreased solubility of CO as the solvent approaches its boiling point. Side reactions of hexacarbonyldicobalt 1,6-enyne complexes in refluxing toluene yield predominantly 1,3-dienes under a nitrogen atmosphere: Krafft, M. E.; Wilson, A. M.; Dasse, O. A.; Bonaga, L. V. R; Cheung, Y. Y.; Fu, Z.; Shao, B.; Scott, I. L. Tetrahedron Lett. 1998, 39, 5911-5914.
16. 4) followed by evaporation of solvent and final purification by flash chromatography on silica gel (15-30% EtOAc /hexane gradient for elution) afforded 111 mg (83%) of enone 1b as a slightly yellow oil. On preparative scale, comparable results can be obtained. Accordingly, a solution of enyne 1a (2.38 g, 10.0 mmol) and dicobalt octcarbonyl (171 mg, 5 mol %) in degassed 1,2-DME (100 mL) was magnetically stirred at room temperature under an atmosphere of CO for 30 min. The resulting solution was then heated for 12 h at 60 °C. The reaction mixture was concentrated in vacuo, and the resulting oil was purified by chromatography on silica gel (0-30% EtOAc/hexane gradient for elution) to afford 2.10 g (79%) of enone 1b as a yellow oil.
17. 8 (Strem Chemical Co., Inc.) that was stored in a Vacuum Atmosphere drybox was utilized.