Mechanistic comparison between Pd-catalyzed ligand-directed C-H chlorination and C-H acetoxylation

Organic Letters

Volumn 11, Issue 20, 2009, Pages 4584-4587

  Stowers, Kara J ^a   Sanford, Melanie S ^a  

^a UNIVERSITY OF MICHIGAN   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CARBON; HYDROGEN; LIGAND; PALLADIUM; SUCCINIMIDE DERIVATIVE;

ARTICLE; CATALYSIS; CHEMISTRY; COMPARATIVE STUDY; HALOGENATION;

CARBON; CATALYSIS; HALOGENATION; HYDROGEN; LIGANDS; PALLADIUM; SUCCINIMIDES;

EID: 70349934422     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol901820w     Document Type: Article

References (48)

1. For reviews, see: (a) Dick, A. R.; Sanford, M. S. Terahedron 2006, 62, 2439.
2. (b)Daugulis, O.: Zaitsev, V. G.; Shabashov. D.; Pham, Q. N.; Lazareva. A. Synlett 2006, 3382.
3. (c)Alberico. D.; Scott, M. E.: Lautens, M. Chem. Rev. 2007, 107, 174.
4. (d)Li. B. J.; Yang, S. D.; Shi, Z. J. Synlett 2008. 949.
5. (e)Chen. X.; Engle, K. M.; Wang. D. H.: Yu, J. Q. Angew, Chem., Int. Ed. 2009, 48, 5094.
6. For examples, see: (a)Desai, L. V.; Hull, K. L.: Sanford, M. S. J. Am. Chem. Soc. 2004, 126. 9542.
7. (b)Giri, R.; Liang. J.; Lei, J. G.; Li, J. J.; Wang, D. H.; Chen, X.; Naggar, I. C.; Guo. C.; Foxman, B. M.: Yu, J. Q. Angew, Chem., Int. Ed. 2005. 44. 7420.
8. (c)Reddy, B. V. S.: Reddy, L. R.: Corey, E. J. Org Lett. 2006. 8. 3391.
9. For examples, see: (a) Dick. A. R.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, /26, 2300.
10. (b)Giri, R.; Chen, X.: Yu, J. Q. Angew Chem., Int, Ed. 2005,44, 2112.
11. (c)Kalyani, D.; Dick, A. R.; Anani, W. Q.; Sanford, M. S. Tetrahedron 2006, 62, 11483.
12. (d)Hull, K. L.: Anani, W. Q.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 7134.
13. (e)Wan. X.; Ma. Z.; Li, B.: Zhang, K.: Cao, S.; Zhang, S.; Shi, Z. J. Am. Chem. Soc. 2006, 128, 7416.
14. (f)Wang, X.; Mei, T. S.; Yu, J. Q. J. Am. Chem. Soc. 2009, 131. 7520.
15. For examples, see: (a)hu, H. Y.; Yu. W. Y.: Che, C. M. J. Am. Chem. Soc. 2006, 28, 9048.
16. (b)Jordon-Hore. J. A.: Johansson. C. C. C.: Gulias, M.: Beck, E. M.; Gaunt, M. J. J. Am. Chem. Soc. 2008, 130, 16184.
17. (c)Mei. T. S.; Wang, X.; Yu. J. Q. J. Am. Chem. Soc. 2009, 131, 10806.
18. (d)Zhao, X.; Dimitrijevic, E.: Dong, V. M. J. Am. Chem. Soc. 2009, 131, 3466.
19. (e)Wasa. M.; Engle, K. M.; Yu. J. Q. J. Am. Chem. Soc. 2009. 131, 9886.
20. (a)Hull, K. L.; Lanni, E. L.: Sanford, M. S. J. Am. Chem. Soc. 2007, 128, 14047.
21. (b)Desai, L. V.; Stowers, K. J.; Sanford. M. S.Sanford J. Am. Soc. 2008. 130, 13285.
22. (c)Hull. K. L.; Sanford, M. S. J. Am. Chem. Soc 2009, ;31, 9651.
23. (d)Racowski. J. M.: Dick. A. R.; Sanford. M. S. J. Am. Chem. Soc. 2009, 131. 10974.
24. (e)Deprez, N. R.: Sanford, M. S. J. Am. Chem. Soc. 2009, 131. 11234.
25. (a)Chiong, H. A.: Pham, Q. N.; Daugulis, O. J. Am. Chem. Soc. 2007, 129, 9879.
26. (b)Li, J. J.; Giri, R.; Yu. J. Q. Inrahedron 2008, 64. 6979.
27. (c)Powers, D. C.; Ritter, T. Nat. Chem. 2009, 1, 302.
28. (d)The identity of the ancillary ligands in the catalytic intermediates is not known; as a result, these ligands are represented as sticks.
29. (e)For the oxidation of a Pd" model complex to PdIV with NCS, see: Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129. 15142.
30. (f)2-Benzylpyridines were used in a previous mechanistic study of Pd-catalyzed C-H acetoxylation (ref 7b). However, these substrates reacted with NCS to form undesired benzylic chlorination side products.
31. 2 catalyst.
32. (h)The kinetic studies were ran at different concentrations (0.024 M for chlorination versus 0.048 M for acetoxylation) because the data for each reaction was significantly more reproducible under these conditions. However, the same kinetic orders and analogous Hammett trends were observed for chlorination at 0.048 M. See the Supporting Information.
33. (i)Intermolecular primary KIE values between 3.58 and 1.85 were observed in the Pd-catalyzed C-H acetoxylation of 2-benzylpyridines (ref 7b).
34. (j)Interpretation of the Hammett data is somewhat complicated by the conjugated biaryl system in 1, since substitution of Y and Z can influence the electronics of both the pyridine (which binds to the metal) and the orthoC-H bond (which undergoes activation). We note that the observed p value for C-H acetoxylation (+0.89 in MeCN) is reasonably similar to that reported for benzylpyridines (+1.40 in benzene, ref 7b), where the pyridine and aryl group are electronically isolated. Thus, we hypothesize that the effect observed here is predominantly due to pyridine electronics.
35. For examples, see: (a) Deeming, A. J.: Rothwell, I. P. ;Organomet. Chem. 1981, 205, 117.
36. (b)Ryabov. A. D.; Sakodinskaya, I. K.; Yatsimirsky, A. K. J. Am. Chem. Soc. Dalton Trans. 1985, 2629.
37. (c)Ryabov, A. D. Chem. Rev. 1990, 90, 403, and references therein.
38. (d)Kurzeev, S. A.; Kazankov. G. M.; Ryabov, A. D. lnorg. Chim. Acta 2002, 340, 192,
39. (e)A dimeric resting state followed by C-H activation at a dimeric intermediate is also possible based on the kinetic data for C-H chlorination. However, literature reports suggest that dimeric complexes like Pd2(X)4(L)2 only predominate in solution under conditions where L:[Pd] < 2:1. Vicente, J.; Saura-Llamas, I. Comments lnorg. Chem. 2007, 28, 39.
40. (f)For examples of cyclometalation mechanisms analogous to path a, see ref 16c as well as:
41. (a)Yatsimirsky, A. K. Zh. Neorg. Khim. 1979, 24, 2711.
42. (b)Yagyu, T.; Aizawa, S.; Funahashi, S. Bull. Chem. Soc. Jpn. 1998, 71, 619.
43. (c)Yagyu, T.; Iwatsuki, S.; Aizawa, S.; Funahashi, S. Bull. Chem. Soc Jpn. 1998, 71, 1857.
44. (d)Martin-Matute, B.; Mateo, C.; Cardenas, D. J.; Echavarren, A. M. Chem.-Eur. J. 2001, 7, 2341.
45. (e)For examples of cyclometalation mechanisms analogous to path b, see:
46. (a)Alsters, P. L.; Engel, P. F.; Hogerheide, M. P.; Copijn, M.; Spek, A. L.; van Koten, G. Qrganometallics 1993, 12, 1831.
47. (b)Otto, S.; Chanda, A.; Samuleev, P. V.; Ryabov, A. D. Eur. J. lnorg. Chem. 2006, 2561, and references therein.
48. 2 should to be fast and essentially quantitative, particularly at 70 °C See refs 16-18.