Asymmetric enamide hydrogenation using planar-chiral cyrhetrenes

Tetrahedron Letters

Volumn 48, Issue 35, 2007, Pages 6189-6191

  Stemmler, René T ^a   Bolm, Carsten ^a  

^a RWTH AACHEN UNIVERSITY   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

ACETAMIDE DERIVATIVE;

ARTICLE; CATALYST; CHIRALITY; HYDROGENATION;

EID: 34547452233     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2007.06.113     Document Type: Article

References (27)

1. For overviews of industrial aspects see:. Jäkel C., and Paciello R. Chem. Rev. 106 (2006) 2912-2942
2. Federsel H.-J. Nat. Rev. Drug Disc. 4 (2005) 685-697
3. Hawkins J.M., and Watson T.J.N. Angew. Chem., Int. Ed. 43 (2004) 3224-3228
4. Angew. Chem. 116 (2004) 3286-3290
5. In: Blaser H.-U., and Schmidt E. (Eds). Asymmetric Catalysis on Industrial Scale (2004), Wiley-VCH, Weinheim, Germany
6. Blaser H.-U. Chem. Commun. (2003) 293-296
7. Blaser H.-U., Spindler F., and Studer M. Appl. Catal. A: Gen. 221 (2001) 119-143
8. For overviews of phosphorous ligands for asymmetric hydrogenation, see:. Tang W., and Zhang X. Chem. Rev. 103 (2003) 3029-3070
9. Blaser H.-U., Malan C., Pugin B., Spindler F., Steiner H., and Studer M. Adv. Synth. Catal. 345 (2003) 103-151
10. 5-cyclopentadienylrhenium(I) tricarbonyl complexes.
11. Bolm C., Xiao L., Hintermann L., Focken T., and Raabe G. Organometallics 23 (2004) 2362-2369
12. Stemmler R.T., and Bolm C. J. Org. Chem. 70 (2005) 9925-9931
13. Stemmler R.T., and Bolm C. Synlett (2007) 1365-1370
14. Preliminary results of the hydrogenation of enamide 6a have been reported earlier, see Ref. 4b.
15. 2Re: C, 57.93; H, 4.48. Found: C, 57.65; H, 4.81.
16. The following enantioselectivities have been achieved: 1a (in DCM): 87% ee; 1b (in EtOAc): 93% ee; 1c (in EtOAc): 77% ee; 1d (in EtOAc): 78% ee.
17. All enamides were prepared according to reported procedures by Burk:. Burk M.J., Wang Y.M., and Lee J.R. J. Am. Chem. Soc. 118 (1996) 5142-5143
18. Burk M.J., Casy G., and Johnson N.B. J. Org. Chem. 63 (1998) 6084-6085
19. 2 as the carrier gas; 49.4 min (minor), 50.7 min (major).
20. ortho-Substituted α-arylenamides are generally challenging substrates in the hydrogenation reaction, and they often lead to low enantiomeric excesses of the corresponding acetamides. The influence of ortho-substitutents has been studied, and alternative modes of coordination of the enamide, which are competitive in the case of ortho-substituted α-arylenamides, were suggested by Imamoto:. Gridnev I.D., Yasutake M., Higashi N., and Imamoto T. J. Am. Chem. Soc. 123 (2001) 5268-5276
21. For examples of insensitive catalyst systems see:. Burk M.J., Wang Y.M., and Lee J.R. J. Am. Chem. Soc. 118 (1996) 5142-5143
22. Zhu G., and Zhang X. J. Org. Chem. 63 (1998) 9590-9593
23. Li W., and Zhang X. J. Org. Chem. 65 (2000) 5871-5874
24. Zeng Q.-H., Hu X.-P., Duan Z.-C., Liang X.-M., and Zheng Z. J. Org. Chem. 71 (2006) 393-396
25. For an example of a catalyst system sensitive to the configuration of the enamide-double bond see:. Imamoto T., Oohara N., and Takahashi H. Synthesis (2004) 1353-1358
26. 2, 80.4 min (minor), 81.0 min (major); 7j: OD-H, Heptan/2-PrOH 90:10, 0.55 mL/min, 210 nm, 28.2 min (minor), 33.3 min (major).
27. */Rh(I) catalyst system, see Ref. 12.