An air-stable palladium/N-heterocyclic carbene complex and its reactivity in aryl amination

Organic Letters

Volumn 4, Issue 13, 2002, Pages 2229-2231

  Viciu, Mihai S ^a   Kissling, Rebecca M ^a   Stevens, Edwin D ^a   Nolan, Steven P ^a  

^a UNIVERSITY OF NEW ORLEANS   (United States)

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ARTICLE;

EID: 0001591967     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol0260831     Document Type: Article

References (37)

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4. (d) Heck, R. F. Palladium Reagents in Organic Synthesis; Academic Press: New York, 1985.
5. See for example: (a) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L. Acc. Chem. Res. 1998, 31, 805-818.
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14. For an in situ catalyst generation, see for example: Harris, M. C.; Buchwald, S. L. J. Org. Chem. 2000, 65, 5327-5333.
15. Recently palladium tertiary phosphine complexes have been used as catalyst precursors in cross-coupling and related chemistry. See for example: Dai, C.; Fu, G. C. J. Am. Chem. Soc. 2001, 123, 2719-2724.
16. For recent reports of defined catalysts for Suzuki coupling, see: (a) Bedford, R. B.; Cazin, C. S. J. Chem. Commun. 2001, 1540-1541.
17. (b) Andreu, M. G.; Zapf, A.; Beller, M. Chem. Commun. 2000, 2475-2476.
18. (a) Huang, J.; Grasa, A.; Nolan, S. P. Org. Lett. 1999, 1, 2053-2055
19. (b) Grasa, G. A.; Viciu, M. S.; Huang, J.; Nolan, S. P. J. Org. Chem. 2001, 66, 7729-7737.
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21. (d) Zhang, C.; Huang, J.; Trudell, M. T.; Nolan, S. P. J. Org. Chem. 1999, 64, 3804-3805
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24. (g) Gradel, B.; Brenner, E.; Schneider, R.; Fort, Y. Tetrahedron Lett. 2001, 42, 5689-5692.
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26. Herrmann has recently reported a palladium complex bearing two bulky NHC leading to a stable Pd(0) complex. Its reactivity has been investigated in Suzuki-Miyaura cross coupling: Gstöttmayr, C. W. K.; Böhn, V. P. W.; Herdtweck, E.; Grosche, M.; Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1363-1365.
27. 7c The ligand precursor (IPr·HCl) can be deprotonated by use of a strong base; see for example: Jafarpour, L.; Stevens, E. D.; Nolan, S. P. J. Organomet. Chem. 2000, 606, 49-54.
28. 2 solution via cannula, and the mixture was stirred for 2 h at room temperature during which time the solution changed color to cloudy dark red-orange. The reaction mixture was filtered through Celite, and 60% of the solvent was removed in vacuo. Hexanes were added with stirring until a persistent precipitate formed (20 mL). The product was collected on a frit and dried in vacuo, yielding a tan-orange powder in 83%.
29. tBu (75% in 1.5 h). The increased solubility of the amylate base in DME may be responsible for the increased reactivity.
30. tAm in DME were made and used over the course of several days' experiments without apparent loss in activity.
31. Hartwig, J. F.; Kawatsura, M.; Hauk, S. I.; Shaughnessy, K. H.; Alcazar-Roman, L. M. J. Org. Chem. 1999, 64, 5575-5580.
32. Alcazar-Roman, L. M.; Hartwig, J. F. J. Am. Chem. Soc. 2001, 123, 12905-12906.
33. See for example: Zhang, X.-X.; Sadighi, J. P.; Mackewitz, T. J.; Buchwald, S. L. J. Am. Chem. Soc. 2000, 122, 7606-7607.
34. tAm in the glovebox. On the bench DME, ArX, and amine (used as received) were added to the open vials. The vials were capped to prevent evaporation and suspended in an 80°C oil bath for the duration of the reaction.
35. (a) Li, G. Y.; Zheng, G.; Noonan, A. F. J. Org. Chem. 2001, 66, 8677-8681.
36. (b) Kwong, F. Y.; Klapars, A.; Buchwald, S. L. Org. Lett. 2002, 4, 581-584.
37. 2 without deleterious effects.