Detection and elimination of product inhibition from the asymmetric catalytic hydrogenation of enamines

Organic Letters

Volumn 7, Issue 22, 2005, Pages 4935-4938

  Hansen, Karl B ^a   Rosner, Thorsten ^a   Kubryk, Michele ^a   Dormer, Peter G ^a   Armstrong III, Joseph D ^a  

^a MERCK RESEARCH LABORATORIES   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMINE; METHANOL; RHODIUM;

ARTICLE; CATALYSIS; CHEMICAL STRUCTURE; CHEMISTRY; HYDROGENATION;

AMINES; CATALYSIS; HYDROGENATION; METHANOL; MOLECULAR STRUCTURE; RHODIUM;

EID: 27644569266     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol051862d     Document Type: Article

References (19)

1. Hsiao, Y.; Rivera, N. R.; Rosner, T.; Krska, S. W.; Njolito, E.; Wang, F.; Sun, Y.; Armstrong, J. D., III.; Grabowski, E. J. J.; Tillyer, R. D.; Spindler, F.; Malan, C. J. Am. Chem. Soc. 2004, 126 (32), 9918-9919.
2. Nishimura, S. Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis; John Wiley & Sons: New York, 2001; Chapter 2.2.1.
3. (a) Marcazzan, P.; Patrick, B. O.; James, B. R. Organometallics 2003, 22, 1177-1179.
4. (b) Marcazzan, P.; Patrick, B. O.; James, B. R. Inorg. Chem. 2004, 43, 6838-6841 and references therein,
5. (c) Faller, J. W.; Tokunaga, M. Tetrahedron Lett. 1993, 34, 7359-7362
6. Ma, J.-A. Angew. Chem., Int. Ed. 2004, 42, 4290-4299
7. For an example of a system that performs the asymmetric reduction of N-acyl enamines with high ee, independent of the E/Z ratio of the enamine, see: Zhou, Y.-G.; Tang, W.; Wang, W.-B.; Li, W.; Zhang, X. J. Am. Chem. Soc. 2002, 124, 4952-4953.
8. The reactions were judged complete when 98% of the total heat flow for the experiment was obtained.
9. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis; John Wiley & Sons: New York, 1999; pp 518-525.
10. Carbon dioxide has been demonstrated to facilitate the reduction of nitriles to amines by protecting the product as a carbamic acid. Xie, X.; Liotta, C. L.; Eckert, C. A. Ind. Eng. Chem. Res. 2004, 43, 7907-7911.
11. 2O.
12. This type of plot provides a graphical equivalent to the rate of reaction versus conversion. See: Landau, R. N.; Blackmond, D. G.; Tung, H.-H. Ind. Eng. Chem. Res. 1994, 33, 814-820.
13. A plot of the differential % thermal conversion as a function of thermal conversion for reactions A, B, and C is contained in the Supporting Information.
14. Coordination of the substrate to catalyst Rh-1a has been proposed in this reaction. See ref 1.
15. a values of TFE and MeOH are 23.5 and 29 in DMSO, respectively. Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456-463.
16. 40 psig can be maintained with a stopper on a glass bottle.
17. A detailed reaction procedure is given in the Supporting Information.
18. The N-Boc amino ester and amide products are easily purified by flash chromatography, in contrast to the unprotected products.
19. The asymmetric hydrogenation of unprotected enamines has been proposed to proceed through the imine tautomer, which results in deuterium incorporation only in the β position of the product.