Asymmetric nickel-catalyzed Negishi cross-couplings of secondary α-bromo amides with organozinc reagents

Journal of the American Chemical Society

Volumn 127, Issue 13, 2005, Pages 4594-4595

  Fischer, Christian ^a   Fu, Gregory C ^a  

^a MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; ASYMMETRIC SYNTHESIS; CATALYST; CHEMICAL REACTION KINETICS; CHEMICAL STRUCTURE; METAL BINDING; ORGANIC CHEMISTRY; PRODUCT RECOVERY; REACTION OPTIMIZATION; STEREOCHEMISTRY; STRUCTURE ANALYSIS;

AMIDES; CATALYSIS; HYDROCARBONS, BROMINATED; NICKEL; ORGANOMETALLIC COMPOUNDS; STEREOISOMERISM; ZINC;

EID: 16844363000     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja0506509     Document Type: Article

References (29)

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2. For pioneering studies of iron-, copper-, and cobalt-catalyzed couplings of Grignard reagents, see: (a) Brinker, U. H.; König, L. Chem. Ber. 1983, 116, 882-893 (iron),
3. (b) Donkervoort, J. G.; Vicario, J. L.; Jastrzebski, J. T. B. H.; Gossage, R. A.; Cahiez, G.; van Koten, G. J. Organomet. Chem. 1998, 555, 61-69 (copper).
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6. (e) Nagano, T.; Hayashi, T. Org. Lett. 2004, 6, 1297-1299 (iron).
7. (f) Martin, R.; Fürstner, A. Angew. Chem., Int. Ed. 2004, 43, 3955-3957 (iron).
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9. (b) (organoboron reagents) Zhou, J.; Fu, G. C. J. Am. Chem. Soc. 2004, 126, 1340-1341.
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11. (d) (organotin reagents) Powell, D. A.; Maki, T.; Fu, G. C. J. Am. Chem. Soc. 2005, 127, 510-511.
12. For examples of other types of metal-catalyzed asymmetric cross-coupling processes, see: (a) Hayashi, T. In Comprehensive Asymmetric Catalysis; Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer: New York, 1999; Chapter 25.
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17. For reviews of applications of oxazoline-based chiral ligands, including pybox, in asymmetric catalysis, see: (a) McManus, H. A.; Guiry, P. J. Chem. Rev. 2004, 104, 4151-4202.
18. (b) Nishiyama, H. In Advances in Catalytic Processes; Doyle, M. P., Ed.; JAI Press: Greenwich, CT, 1997; Volume 2, pp 153-188.
19. 2·diglyme can also be used, although they are somewhat less effective.
20. (b) (i-Pr)-Pybox, unlike (s-Bu)-Pybox, is commercially available.
21. (c) We have not been able to employ commercially available HexZnBr (Aldrich) in this process. We recommend that pure organozinc reagents be prepared from the corresponding alkyl bromides according to the straightforward procedure of Huo: Huo, S. Org. Lett. 2003, 5, 423-425.
22. (d) At room temperature, the product is generated in 91% ee. At -20 °C, the cross-coupling process is slow.
23. 2O) to remove inorganic salts and most of the DMI. The filtrate was concentrated, and the resulting orange oil was purified by flash chromatography.
24. Notes: (a) The yield of the reaction is sensitive to the steric demand of the coupling partners. Thus, we have not been able to efficiently cross-couple a secondary organozinc reagent or an α-isopropyl-α-bromo amide.
25. (b) Under the standard conditions, benzylzinc reagents are not suitable substrates.
26. (c) For the cross-coupling illustrated in entry 1 of Table 1, when the reaction is run on a 10 mmol scale, we obtain the product in 88% yield (3.0 g) and 95% ee.
27. (d) The process is not highly sensitive to oxygen or moisture; when we conduct a coupling under air in a closed vial with 1.6 equiv of the organozinc reagent, we obtain essentially identical yield and enantiomeric excess.
28. (e) Under identical conditions, α-bromoesters furnish lower yield and lower enantiomeric excess.
29. Anderson, T. J.; Jones, G. D.; Vicic, D. A. J. Am. Chem. Soc. 2004, 126, 8100-8101.