Catalytic synthesis of γ-lactams via direct annulations of enals and N-sulfonylimines

Organic Letters

Volumn 7, Issue 14, 2005, Pages 3131-3134

  He, Ming ^a   Bode, Jeffrey W ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 22244447100     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol051234w     Document Type: Article

References (26)

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15. Only a few reports on the use of 4-methoxybenzenesulfonyl imines as electrophiles have appeared. In both cases, these provided few or no advantages over the N-tosyl imines. See: (a) Fujihara, H.; Nagai, K.; Tomioka, K. J. Am. Chem. Soc. 2000, 122, 12055-12056.
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17. For experiments and spectral data, see Supporting Information. Further studies on the mechanism and kinetics of the reversible addition of the catalyst to the imine are in progress.
18. Typical Procedure for Catalytic Annulations. Cinnamaldehyde (0.90 7, 6.8 mmol, 1.0 equiv), imine 13 (2.05 g, 6.8 mmol, 1.0 equiv), and IMes-Cl (0.35 g, 1.0 mmol, 15 mol %) were weighed into an oven-dried flask. The flask was sealed with a septum, evacuated, and back-filled with argon. To this mixture was added 68 mL of tert-BuOH followed by DBU (0.10 mL, 0.68 mmol, 10 mol %), and the resulting solution was stirred for 14 h at 25°C. The reaction was concentrated under reduced pressure and purified by flash chromatography (4:1 hexane/EtoAc) to afford the lactam products as a white solid (1.8 g, 61% yield, 8/1 cis:trans).
19. 1H NMR NOE studies (See Supporting Information) and comparison to known lactams products: (a) Escalante, J.; Gonzálex-Tototzin, M. A. Tetrahedron: Asymmetry 2003, 14, 981-985.
20. (b) Yee, N. K.; Nummy, L. J.; Byrne, D. P. J. Org. Chem. 1998, 63, 326-330.
21. Imine decomposition and unreacted enal constitute the mass balance.
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24. (c) For the protonation of catalytically generated homoenolates by phenols, see: Chan, A.; Scheidt, K. A. Org. Lett. 2005, 7, 905-908.
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