Highly Enantioselective diels-alder reactions of maleimides catalyzed by activated chiral oxazaborolidines

Organic Letters

Volumn 12, Issue 3, 2010, Pages 632-635

  Mukherjee, Santanu ^a   Corey, E J ^a  

^a HARVARD UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALKENE; BORON DERIVATIVE; MALEIMIDE DERIVATIVE;

ARTICLE; CATALYSIS; CHEMICAL STRUCTURE; CHEMISTRY; CYCLIZATION; STEREOISOMERISM;

ALKENES; BORON COMPOUNDS; CATALYSIS; CYCLIZATION; MALEIMIDES; MOLECULAR STRUCTURE; STEREOISOMERISM;

EID: 75749121796     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol902865d     Document Type: Article

References (20)

1. Corey, E. J.; Shibata, T.; Lee, T. W. J. Am. Chem. Soc. 2002, 124, 3808-3809
2. Canales, E.; Corey, E. J. Org. Lett. 2008, 10, 3271-3273.
3. Liu, D.; Canales, E.; Corey, E. J. J. Am. Chem. Soc. 2007, 129, 1498-1499.
4. Corey, E. J. Angew. Chem. Int. Ed. 2009, 48, 2100-2117,
5. Also see: Corey, E. J. Angew. Chem. Int. Ed. 2002, 41, 1650-1667.
6. (a) Tripathy, R.; Carroll, P. J.; Thornton, E. R. J. Am. Chem. Soc. 1991, 113, 7630-7640.
7. (b) Menezes, R. F.; Zezza, C. A.; Sheu, J.; Smith, M. B. Tetrahedron Lett. 1989, 30, 3295-3298, and the references therein.
8. Corey, E. J.; Sarshar, S.; Lee, D.-H. J. Am. Chem. Soc. 1994, 116, 12089-12090.
9. Corey, E. J.; Letavic, M. A. J. Am. Chem. Soc. 1995, 117, 9616-9617.
10. Soh, J. Y.-T.; Tan, C.-H. J. Am. Chem. Soc. 2009, 131, 6904-6905.
11. Twenty mol percent catalyst was used typically for faster reaction. It is possible to reduce the catalyst loading to 10 mol % without affecting the reaction yield and enantioselectivity. However, in these cases reactions must be carried out in more concentrated solution (1.0 M instead of 0.5 M).
12. Adams, D. J.; Blake, A. J.; Cooke, P. A.; Gill, C. D.; Simpkins, N. S. Tetrahedron 2002, 58, 4603-4-615. Also see Supporting Information.
13. 2O (2 mL), allowed to warm to ambient temperature and filtered through a Celite pad. The filtrate was concentrated in vacuo and the residue purified by silica gel column chromatography using hexanes/EtOAc (5:1 to 3:1) to obtain, as a white crystalline solid, the desired product 6a (117 mg, 0.46 mmol, 92% yield; mp 124-125 °C). For further details about determination of enantiomeric purity by HPLC-analysis, see Supporting Information.
14. 2O (2 mL), brought to ambient temperature and filtered through a Celite pad. The filtrate was concentrated to a colorless oil. 1H-NMR analysis of the crude product revealed a 6:1 ratio of 10 and 11. Purification by silica gel column chromatography using hexanes/EtOAc (5:1 to 4:1 to 3:1) afforded, as colorless crystals, 10 (mp 141-143 °C) and 11 (mp 193-195 °C). For further details about determination of enantiomeric purity by HPLCanalysis, see Supporting Information.
15. For a recent report on asymmetric Diels-Alder reactions of substituted cyclopentadiene see: Payette, J. N.; Yamamoto, H. J. Am. Chem. Soc. 2007, 129, 9536-9537.
16. Reaction was slow and interrupted before completion (approximately 80% conversion).
17. For determination of enantiomeric purity and absolute configuration, see Supporting Information.
18. Experimental procedure for the preparation of 1: (S)-1.1- Diphenylpyrrolidinemethanol 15 (697 mg; 2.75 mmol) was placed in a 25 mL oven- and flame-dried round bottom flask together with 2.5 mL abs. benzene and Hünig's base (0.96 mL; 5.50 mmol) under nitrogen. A solution of dibromo(o-tolyl)borane 14 (720 mg; 2.75 mmol) in 2.5 mL abs. benzene was added via syringe over 30 min at rt. After the addition was complete, the resulting white suspension was heated at 40 °C for 1 h. The reaction mixture was cooled to ambient temperature and the precipitate was filtered through a sintered glass funnel under nitrogen. The filtrate was concentrated under reduced pressure to a pale yellow oil, which was taken in abs. toluene to make a 0.25M solution of 1 and used subsequently for Diels-Alder experiments. Also see Supporting Information.
19. Ryu, D. H.; Lee, T. W.; Corey, E. J. J. Am. Chem. Soc. 2002, 124, 9992-9993.
20. Also see: Chein, R. J.; Yeung, Y.-Y.; Corey, E. J. Org. Lett. 2009, 11, 1611-1614.