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Volumn 131, Issue 31, 2009, Pages 10974-10983

Detailed study of C-O and C-C bond-forming reductive elimination from stable C2N2O2-ligated palladium(IV) complexes

Author keywords

[No Author keywords available]

Indexed keywords

BOND FORMING; C-C BONDS; CYCLOMETALATED LIGAND; HAMMETT PLOTS; REDUCTIVE ELIMINATION;

EID: 68249154737     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja9014474     Document Type: Article
Times cited : (329)

References (75)
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    • 2, see: (a) Dick, A. R.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300.
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    • For examples of directed C-H bond acetoxylation with other oxidants, see: (a) 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
    • For examples of directed C-H bond acetoxylation with other oxidants, see: (a) 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.
  • 10
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    • For examples of other PdII/IV-catalyzed acetoxylation reactions using PhI(OAc)2, see: (a) Alexanian, E. J, Lee, C, Sorensen, E. J. J. Am. Chem. Soc. 2005, 127, 7690
    • 2, see: (a) Alexanian, E. J.; Lee, C.; Sorensen, E. J. J. Am. Chem. Soc. 2005, 127, 7690.
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    • 2. See: Yoneyama, T.; Crabtree, R. H. J. Mol. Catal. A 1996, 108, 35.
    • 2. See: Yoneyama, T.; Crabtree, R. H. J. Mol. Catal. A 1996, 108, 35.
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    • IV complexes containing O-donor ligands were detected at low temperature, see: (a) Canty, A. J.; Jin, H. J. Organomet. Chem. 1998, 565, 135.
    • IV complexes containing O-donor ligands were detected at low temperature, see: (a) Canty, A. J.; Jin, H. J. Organomet. Chem. 1998, 565, 135.
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    • For examples of rigid bidentate ligands stabilizing PdIV complexes, see: (a) Canty, A. J. Acc. Chem. Res. 1992, 25, 83
    • IV complexes, see: (a) Canty, A. J. Acc. Chem. Res. 1992, 25, 83.
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    • IV center, see: Byers, P. K.; Canty, A. J.; Skelton, B. W.; White, A. H. J. Chem. Soc., Chem. Commun. 1986, 1722. For numerous more recent examples, see refs 8, 9.
    • IV center, see: Byers, P. K.; Canty, A. J.; Skelton, B. W.; White, A. H. J. Chem. Soc., Chem. Commun. 1986, 1722. For numerous more recent examples, see refs 8, 9.
  • 48
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    • IV complexes stabilized by cyclometalated ligands, see: (a) Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 15142.
    • IV complexes stabilized by cyclometalated ligands, see: (a) Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 15142.
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    • Ph.D. Thesis, University of Michigan
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    • 3) with the corresponding silver carboxylate. See the Supporting Information for full details.
    • 3) with the corresponding silver carboxylate. See the Supporting Information for full details.
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    • Isaacs, N. S. Physical Organic Chemistry, 2nd ed.; Pearson Education: New York, 1995.
    • Isaacs, N. S. Physical Organic Chemistry, 2nd ed.; Pearson Education: New York, 1995.
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    • Initial investigations revealed that clean first order kinetics were not observed in some solvents, and we hypothesized that this might be due to formation of a highly reactive 3-coordinate PdII intermediate. Closely related challenges have been observed in reductive elimination reactions from PdII centers (for example, see ref 19a) and have been resolved by the addition of external ancillary ligands, which serve to trap unsaturated intermediates. Similarly, we found that the addition of 5% of pyridine-d5 to the reductive elimination reactions of 7 in each solvent resulted in clean first order kinetics over greater than three half-lives. Qualitative time studies showed that added pyridine had little effect on the relative rate in each of the solvents studied
    • 5 to the reductive elimination reactions of 7 in each solvent resulted in clean first order kinetics over greater than three half-lives. Qualitative time studies showed that added pyridine had little effect on the relative rate in each of the solvents studied.
  • 69
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    • Carboxylate exchange in toluene progressed too slowly to measure quantitatively at -38°C (i.e., no observable exchange occurred after 6 h).
    • Carboxylate exchange in toluene progressed too slowly to measure quantitatively at -38°C (i.e., no observable exchange occurred after 6 h).
  • 70
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    • More investigation is needed to understand why the entropy of activation is so small in this system. See ref 34 for a possible explanation
    • More investigation is needed to understand why the entropy of activation is so small in this system. See ref 34 for a possible explanation.
  • 72
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    • 2 have the added complication that these complexes contain two different carboxylate ligands. If mechanism A were operating, these two ligands would serve two very different roles in the first step of the reaction - one would dissociate to form an anion (stabilized by electron withdrawing groups), while the other would remain bound to cationic intermediate II (stabilized by electron donating groups).
    • 2 have the added complication that these complexes contain two different carboxylate ligands. If mechanism A were operating, these two ligands would serve two very different roles in the first step of the reaction - one would dissociate to form an anion (stabilized by electron withdrawing groups), while the other would remain bound to cationic intermediate II (stabilized by electron donating groups).
  • 73
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    • ‡ = 31.4 and 26.4 kcal/mol, respectively). In contrast, mechanism C was calculated to have a much larger activation energy of 44.3 kcal/mol.
    • ‡ = 31.4 and 26.4 kcal/mol, respectively). In contrast, mechanism C was calculated to have a much larger activation energy of 44.3 kcal/mol.
  • 74
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    • While the observed solvent effects and activation parameters are somewhat unexpected for a system involving ionic intermediates, they may result from an unusually early or late transition state that has relatively little charge buildup
    • While the observed solvent effects and activation parameters are somewhat unexpected for a system involving ionic intermediates, they may result from an unusually early or late transition state that has relatively little charge buildup.
  • 75
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    • Only C-O coupled products were formed in this reaction; however, both acetoxylated product 73 and the corresponding phenol (presumably formed by ester hydrolysis under the reaction conditions) were observed.
    • Only C-O coupled products were formed in this reaction; however, both acetoxylated product 73 and the corresponding phenol (presumably formed by ester hydrolysis under the reaction conditions) were observed.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.