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Synthesis 2001(8): 1268-1274
DOI: 10.1055/s-2001-15067
PAPER
© Georg Thieme Verlag Stuttgart · New York

Solvent Trapping of Photochemically Generated Pyran-4-one-Derived Oxyallyls: A Convenient Cyclopentannulation Method

Mike Fleming, Peter V. Fisher, Gamini U. Gunawardena, Yinghua Jin, Chen Zhang, Wei Zhang, Atta M. Arif, Frederick G. West*
Department of Chemistry, University of Utah, 315 S. 1400 East, Rm. 2020, Salt Lake City, UT, USA 84112-0850
Fax: +1(801)5818433; e-Mail: west@chemistry.chem.utah.edu;
Further Information

Publication History

Received 5 March 2001
Publication Date:
24 September 2004 (online)

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Abstract

Fused bicyclic pyran-4-ones 2a-f are readily available via one-step annulation with diketene or diketene equivalents. Irradiation of 2b-e in methanol furnished ring-contracted solvent adducts 4 in moderate yields, whereas irradiation in aqueous H2SO4 gave the corresponding glycols 8 and 9. The unusual predominance of cis-fused product 8b appears to result from in situ acid-catalyzed equilibration. Substrate 2f could also be trapped in aqueous acid, and displayed a modest stereoselectivity that may derive from conformational control by the methyl group on the starting material’s stereogenic center.

Key Words

annulations - bicyclic compounds - diols - heterocycles - photochemistry - ring contractions

    References and Notes

  • 1a Zimmerman HE. Lynch DC. J. Am. Chem. Soc.  1985,  107:  7745 
    CrossrefGoogle Scholar
  • 1b Nuss JM. West FG. In The Chemistry of Dienes and Polyenes   Rappoport Z. Wiley; Chichester: 1997.  p.263-324  
    CrossrefGoogle Scholar
  • 2 West FG. In Advances in Cycloaddition   Vol. 4:  Lautens M. JAI Press; Greenwich, CT: 1997.  p.1-40  
    Google Scholar
  • 3a Barltrop JA. Day AC. Samuel CJ. J. Am. Chem. Soc.  1979,  101:  7521 
    Google Scholar
  • 3b Pavlik JW. Keil EB. Sullivan EL. J. Heterocycl. Chem.  1992,  29:  1829 
    Google Scholar
  • 3c Pavlik JW. Kirincich SJ. Pires RM. J. Heterocycl. Chem.  1991,  28:  537 
    Google Scholar
  • 4 West FG. Fisher PV. Gunawardena GU. Mitchell S. Tetrahedron Lett.  1993,  34:  4583 
    CrossrefGoogle Scholar
  • 5 Hünig S. Benzing E. Hübner K. Chem. Ber.  1961,  94:  486 
    Google Scholar
  • 6a Coleman RS. Grant EB. Tetrahedron Lett.  1990,  31:  3677 
    Google Scholar
  • 6b Sato M. Ogasawara H. Kato K. Sakai M. Kato T. Chem. Pharm. Bull.  1983,  31:  4300 
    Google Scholar
  • Notably, intermolecular trapping of non-photochemically generated oxyallyl cations seems to favor attack at the less substituted terminus:
  • 7a Noyori R. Shimizu F. Fukuta K. Takaya H. Hayakawa Y. J. Am. Chem. Soc.  1977,  99:  5196 
    CrossrefGoogle Scholar
  • 7b Giese S. Kastrup L. Stiens D. West FG. Angew. Chem. Int. Ed.  2000,  40:  1970 
    CrossrefGoogle Scholar
  • 7c Giese S. West FG. Tetrahedron  2000,  56:  10221 
    CrossrefGoogle Scholar
  • 8 For an earlier report of in situ Norrish type II cleavage in a similar system, see: Keil EB. Pavlik JW. J. Heterocycl. Chem.  1976,  13:  1149 
    Google Scholar
  • 9 Barltrop JA. Barrett JC. Carder RW. Day AC. Harding JR. Long WE. Samuel CJ. J. Am. Chem. Soc.  1979,  101:  7510 
    CrossrefGoogle Scholar
  • 10 Pavlik JW. Spada AP. Snead TE. J. Org. Chem.  1985,  50:  3046 
    Google Scholar
  • 17 Takeuchi N. Nakagawa H. Kamisato M. Tobinaga S. Chem. Pharm. Bull.  1980,  2460 
    Google Scholar
11

Molecular mechanics calculations (AM1)indicate that cis-isomer 8b is more stable than trans-isomer 9b by as much as 12 kcal/mol.

12

In contrast, trans-isomers 9c and 9d did not undergo any isomerization under the reaction conditions.

13

X-ray diffraction data for 4e, 8d and 8f have been deposited with the Cambridge Crystallographic Data Centre (deposition numbers CCDC 158715, CCDC 158907 and CCDC 158908, respectively).

14

Hydroxyl proton assignments were confirmed by D2O exchange. In acetone-d 6, the hydroxyl protons of both cis-8 and trans-9 all appeared downfield of 4 ppm.

15

Higher concentrations of H2SO4 led to variable product ratios, presumably via acid-catalyzed isomerization as noted with 8b/9b.

16

The UV absorbance data for known compounds 2a,b have been previously reported: 2a (MeOH): λmax 252 nm (e = 12.6 × 103 cm-1M-1); [5] 2b (MeOH): λmax 252 nm (e = 13.6 × 103 cm-1M-1); [5] 2b (EtOH): λmax 252 (e = 5.6 × 103 cm-1M-1). [17] The data for 2c-f are: 2c (MeOH): λmax 256 nm (e = 10.2 × 103 cm-1M-1); 2d (MeOH): λmax 256 nm
(10-5 M; e = 11.4 × 103 cm-1M-1); 2e (MeOH): λmax 256 nm (10-5 M; e = 11.1 × 103 cm-1M-1); 2f (EtOH): λmax 262 nm (e = 7.5 × 103 cm-1M-1.