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33646064214
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4
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34247472772
-
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4- tetraphenylcyclobutadiene)cobalt]-dipalladium. This catalyst is commercially available from Aldrich.
-
4- tetraphenylcyclobutadiene)cobalt]-dipalladium. This catalyst is commercially available from Aldrich.
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6
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33947092413
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20
-
-
0027288055
-
-
The thermal diastereoselective allylic trichloroacetimidate rearrangement has been computationally studied using semiempirical methods. See: Eguchi, T, Koudate, T, Kakinuma, K. Tetrahedron 1993, 49, 4527-4540
-
The thermal diastereoselective allylic trichloroacetimidate rearrangement has been computationally studied using semiempirical methods. See: Eguchi, T.; Koudate, T.; Kakinuma, K. Tetrahedron 1993, 49, 4527-4540.
-
-
-
-
21
-
-
0037458598
-
-
2-catalyzed allylic N-(p-methoxyphenyl) benzimidate rearrangement was proposed. See: Kang, J.; Kim, T. H.; Yew, K. H.; Lee, W. K. Tetrahedron: Asymmetry 2003, 14, 415-418.
-
2-catalyzed allylic N-(p-methoxyphenyl) benzimidate rearrangement was proposed. See: Kang, J.; Kim, T. H.; Yew, K. H.; Lee, W. K. Tetrahedron: Asymmetry 2003, 14, 415-418.
-
-
-
-
22
-
-
33748551071
-
-
After the present study was completed, the Peters research group published a model for the enantioselectivity observed in the allylic N-(p-methoxyphenyl)trifluoroacetimidate rearrangement catalyzed by a palladium(II) compound with a ferrocenium-based chiral ligand. Their model is based upon structure-activity relationships of systematically varied catalysts. See: Weiss, M. E.; Fischer, D. F.; Xin, Z.-Q.; Jautze, S.; Schweizer, W. B.; Peters, R. Angew. Chem., Int. Ed. 2006, 45, 5694-5698.
-
After the present study was completed, the Peters research group published a model for the enantioselectivity observed in the allylic N-(p-methoxyphenyl)trifluoroacetimidate rearrangement catalyzed by a palladium(II) compound with a ferrocenium-based chiral ligand. Their model is based upon structure-activity relationships of systematically varied catalysts. See: Weiss, M. E.; Fischer, D. F.; Xin, Z.-Q.; Jautze, S.; Schweizer, W. B.; Peters, R. Angew. Chem., Int. Ed. 2006, 45, 5694-5698.
-
-
-
-
23
-
-
34247469994
-
-
1,3,5-Trimethoxybenzene was used as an NMR internal standard.
-
1,3,5-Trimethoxybenzene was used as an NMR internal standard.
-
-
-
-
24
-
-
34247489478
-
-
We make the assumption that fragmentation of alkylpalladium intermediate 19 is rapid based on the exothermicity of the overall reaction, which is thermodynamically favored by approximately 14 kcal/mol (see ref 16, If formation of alkylpalladium intermediate 19 were rate-determining, then its fragmentation to form the C=O bond will have an early transition state, close in energy to intermediate 19. Our computations (discussed below) are in agreement with this assumption. Alternatively, we could assume that formation of η2-(alkene)palladium intermediate 20 is the first irreversible step. This would add a k3 term to our general rate law but would not alter the rate dependence on catalyst, imidate, or chloride
-
3 term to our general rate law but would not alter the rate dependence on catalyst, imidate, or chloride.
-
-
-
-
25
-
-
0000176481
-
-
Conversion of the imidate to the amide is thermodynamically favored by about 14 kcal/mol. See: (a) Beak, P.; Bonham, J.; Lee, J. T. J. Am. Chem. Soc. 1968, 90, 1569-1582.
-
Conversion of the imidate to the amide is thermodynamically favored by about 14 kcal/mol. See: (a) Beak, P.; Bonham, J.; Lee, J. T. J. Am. Chem. Soc. 1968, 90, 1569-1582.
-
-
-
-
27
-
-
0010851829
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-
(c) Beak, P.; Lee, J.-K.; Zeigler, J. M. J. Org. Chem. 1978, 43, 1536-1538.
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-
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Beak, P.1
Lee, J.-K.2
Zeigler, J.M.3
-
28
-
-
34247519849
-
-
This analysis assumes that olefin displaces chloride in an associative manner. Another possibility is reversible dissociation of chloride followed by palladium-olefin coordination in an independent elementary step. This mechanism is unlikely, because ligand dissociation from a 16-electron palladium(II) complex creates a 14-electron, coordinatively unsaturated intermediate. In general, associative pathways for ligand substitution are strongly favored for palladium(II) complexes. See: Crabtree, R. H. The Organometallic Chemistry of the Transition Metals, 2nd ed, John Wiley & Sons, Inc, New York, 1994; pp 89-90
-
This analysis assumes that olefin displaces chloride in an associative manner. Another possibility is reversible dissociation of chloride followed by palladium-olefin coordination in an independent elementary step. This mechanism is unlikely, because ligand dissociation from a 16-electron palladium(II) complex creates a 14-electron, coordinatively unsaturated intermediate. In general, associative pathways for ligand substitution are strongly favored for palladium(II) complexes. See: Crabtree, R. H. The Organometallic Chemistry of the Transition Metals, 2nd ed.; John Wiley & Sons, Inc.: New York, 1994; pp 89-90.
-
-
-
-
29
-
-
34247533479
-
-
Nonlinear decay and growth curves were fit using: KaleidaGraph, version 3.6, Synergy Software: Reading, PA, 2003
-
Nonlinear decay and growth curves were fit using: KaleidaGraph, version 3.6.; Synergy Software: Reading, PA, 2003.
-
-
-
-
31
-
-
34247542301
-
-
The concentration of tetrabutylammonium hexafluorophosphate was varied from 12-48 mM at constant concentrations of imidate 2a (117 mM), dichloropalladate 5e (9.0 mM), and tetrabutylammonium chloride (24 mM).
-
The concentration of tetrabutylammonium hexafluorophosphate was varied from 12-48 mM at constant concentrations of imidate 2a (117 mM), dichloropalladate 5e (9.0 mM), and tetrabutylammonium chloride (24 mM).
-
-
-
-
33
-
-
0027370376
-
-
Gepasi, version 3.3, was employed in these simulations. See: (a) Mendes, P. Comput. Appl. Biosci. 1993, 9, 563-571
-
Gepasi, version 3.3, was employed in these simulations. See: (a) Mendes, P. Comput. Appl. Biosci. 1993, 9, 563-571.
-
-
-
-
36
-
-
34247470457
-
-
0 = 0 mM. The initial concentration of all other metabolites was defined to be 0 mM.
-
0 = 0 mM. The initial concentration of all other metabolites was defined to be 0 mM.
-
-
-
-
37
-
-
34247545879
-
-
While we attained a good fit using these randomly chosen values, a good fit was also attained using different initial guesses for these rate constants, provided that the equilibria in steps 1, 2, and 5 were established rapidly compared to the rate of step 3. For example, an equally good fit was attained using the following initial values: k1, 0.1 mM -2·min-1; k-1, 500 mM -1·min-1; k2, 0.1 mM -2·min-1; k-2, 2 ± 106 mM-1·min-1; k5, 5000 mM-1·min-1; k-5, 0.1 mM-2·min-1. Similarly, a good fit was attained using these initial values: k1, 10 000 mM -2·min-1; k-1, 50 000 000 mM-1·min-1; k
-
-1. Because a good fit does not depend on the absolute value of these rate constants, these kinetic simulations do not provide the absolute values of these constants.
-
-
-
-
38
-
-
34247528737
-
-
We assume that the fragmentation of alkylpalladium intermediate 26 is more facile than its formation. This assumption is supported by our computational studies below
-
We assume that the fragmentation of alkylpalladium intermediate 26 is more facile than its formation. This assumption is supported by our computational studies below.
-
-
-
-
39
-
-
34247503435
-
-
The rate constants and graphs comparing the experimental and simulated data for each data set are included in the Supporting Information
-
The rate constants and graphs comparing the experimental and simulated data for each data set are included in the Supporting Information.
-
-
-
-
40
-
-
34247538149
-
-
-5) were randomly made. However, none of our numerous initial guesses provided a good fit between the simulated and experimental concentration of nitrogen-bound palladium adduct 21b.
-
-5) were randomly made. However, none of our numerous initial guesses provided a good fit between the simulated and experimental concentration of nitrogen-bound palladium adduct 21b.
-
-
-
-
41
-
-
34247466194
-
-
As before, we assume that the binding constant of the terminal olefinic group of amide 3a is approximately equal to the binding constant of (Z)-2-hexene.
-
As before, we assume that the binding constant of the terminal olefinic group of amide 3a is approximately equal to the binding constant of (Z)-2-hexene.
-
-
-
-
42
-
-
34247506034
-
-
13C NMR, IR, and mass spectroscopy as well as elemental analysis. In addition, X-ray crystallographic analysis of benzoxazole-bound palladium monomer 28 showed that benzoxazole is bound trans to the oxazoline ligand. See the Supporting Information for details.
-
13C NMR, IR, and mass spectroscopy as well as elemental analysis. In addition, X-ray crystallographic analysis of benzoxazole-bound palladium monomer 28 showed that benzoxazole is bound trans to the oxazoline ligand. See the Supporting Information for details.
-
-
-
-
43
-
-
84877935319
-
-
These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
-
CCDC 626772 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
-
CCDC 626772 contains the supplementary crystallographic data for this paper
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44
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0000189651
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For information on the B3LYP functional, see: (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
-
For information on the B3LYP functional, see: (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
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33751157732
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Jaguar 5.5, release 11; Schrödinger, L.L.C.: Portland, OR, 1991-2003.
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2-(alkene) palladium compounds, the four Pd-C distances in cyclooctadienylpalladium(II) chloride were determined to be 2.200, 2.209, 2.211, and 2.259 Å by X-ray crystallography. See: Rettig, M. F.; Wing, R. M.; Wiger, G. R. J. Am. Chem. Soc. 1981, 103, 2980-2986.
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2-(alkene) palladium compounds, the four Pd-C distances in cyclooctadienylpalladium(II) chloride were determined to be 2.200, 2.209, 2.211, and 2.259 Å by X-ray crystallography. See: Rettig, M. F.; Wing, R. M.; Wiger, G. R. J. Am. Chem. Soc. 1981, 103, 2980-2986.
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56
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34247508318
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See the Supporting Information for details
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See the Supporting Information for details.
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57
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0001724007
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65
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33847087937
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Examples of C-N bond distances in simple molecules include 1.474, 1.462, and 1.451 Å. See: Dewar, M. J. S.; Thiel, W. J. Am. Chem. Soc. 1977, 99, 4907-4917.
-
Examples of C-N bond distances in simple molecules include 1.474, 1.462, and 1.451 Å. See: Dewar, M. J. S.; Thiel, W. J. Am. Chem. Soc. 1977, 99, 4907-4917.
-
-
-
-
66
-
-
34247480654
-
-
See the Supporting Information for details
-
See the Supporting Information for details.
-
-
-
-
67
-
-
0042964469
-
-
2-(alkene) palladium compounds, the four Pd-C distances in cyclooctadienylpalladium(II) chloride were determined to be 2.200, 2.209, 2.211, and 2.259 Å by X-ray crystallography. See: Rettig, M. F.; Wing, R. M.; Wiger, G. R. J. Am. Chem. Soc. 1981, 103, 2980-2986.
-
2-(alkene) palladium compounds, the four Pd-C distances in cyclooctadienylpalladium(II) chloride were determined to be 2.200, 2.209, 2.211, and 2.259 Å by X-ray crystallography. See: Rettig, M. F.; Wing, R. M.; Wiger, G. R. J. Am. Chem. Soc. 1981, 103, 2980-2986.
-
-
-
-
68
-
-
34247548940
-
-
From the preceding π-complexed palladium intermediates, the activation energies for these transition states were calculated to be 11.9 kcal/mol for transition structure 37, 16.3 kcal/mol for transition structure 38, 16.4 kcal/ mol for transition structure 39, and 11.5 kcal/mol for transition structure 40.
-
From the preceding π-complexed palladium intermediates, the activation energies for these transition states were calculated to be 11.9 kcal/mol for transition structure 37, 16.3 kcal/mol for transition structure 38, 16.4 kcal/ mol for transition structure 39, and 11.5 kcal/mol for transition structure 40.
-
-
-
-
69
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34247508789
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-
Ph.D. Dissertation, University of California, Irvine, CA
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Anderson, C. E. Ph.D. Dissertation, University of California, Irvine, CA, 2003.
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(2003)
-
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Anderson, C.E.1
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70
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34247487138
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-
As with [COP-Cl]2, the [COP-OCOCF3] 2-catalyzed rearrangement of electron-poor N-(p-methoxyphenyl) trifluoroacetimidates proceeds more quickly for E olefins than for Z. See ref 4i. In contrasting the reactivity of trifluoroacetimidates and benzimidates, then, the difference in relative rearrangement rates of E vs Z olefins most likely arises from differing nucleophilicity of the imidate nitrogen
-
2-catalyzed rearrangement of electron-poor N-(p-methoxyphenyl) trifluoroacetimidates proceeds more quickly for E olefins than for Z. See ref 4i. In contrasting the reactivity of trifluoroacetimidates and benzimidates, then, the difference in relative rearrangement rates of E vs Z olefins most likely arises from differing nucleophilicity of the imidate nitrogen.
-
-
-
-
72
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-
34247527083
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The magnitude of the energy difference between calculated transition-state structures 37 and 40 is 1.6 kcal/mol. This value is in close agreement to the ΔΔG‡ measured by the experimentally determined enantiomeric ratio (2.0 kcal/mol at 298 K). Because the entropy of these transition-state structures should be similar, the electronic energies plus zero-point corrections should correlate with the relative Gibbs free energies.
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The magnitude of the energy difference between calculated transition-state structures 37 and 40 is 1.6 kcal/mol. This value is in close agreement to the ΔΔG‡ measured by the experimentally determined enantiomeric ratio (2.0 kcal/mol at 298 K). Because the entropy of these transition-state structures should be similar, the electronic energies plus zero-point corrections should correlate with the relative Gibbs free energies.
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73
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85026878649
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(a) Anderson, C. E.; Overman, L. E.; Richards, C. J.; Watson, M. P.; White, N. Org. Synth. 2007, 84, 139-147.
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(2007)
Org. Synth
, vol.84
, pp. 139-147
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Anderson, C.E.1
Overman, L.E.2
Richards, C.J.3
Watson, M.P.4
White, N.5
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85026850769
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(b) Anderson, C. E.; Kirsch, S. F.; Overman, L. E.; Richards, C. J.; Watson, M. P. Org. Synth. 2007, 84, 148-155.
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(2007)
Org. Synth
, vol.84
, pp. 148-155
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Anderson, C.E.1
Kirsch, S.F.2
Overman, L.E.3
Richards, C.J.4
Watson, M.P.5
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75
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34247483714
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In addition to improving COP-based catalysts, this mechanistic model may also account for recently reported results (see ref 13, The Peters group tested a variety of ferrocenium-imidazoline palladacycles in the rearrangement of allylic N-(p-methoxyphenyl)trifluoroacetimidales. Whereas varying the imidazoline substituents had little effect on the enantioselectivity, increasing the size of the substituent on the terminal cyclopentadienyl ring led to substantially improved enantioselectivity. Our model for enantioinduction is consistent with these results. In the enantiodetermining step, the allylic trifluoroacetimidate fragment is bound trans to the imidazolinyl fragment. Enantioselectivity arises because the transition-state structure leading to the minor enantiomer is disfavored by steric hindrance between the C3-substituent of the allylic imidate fragment and the C5R5 fragment of the catalyst. This explanation assumes that the rate-determining step of the
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5 fragment of the catalyst. This explanation assumes that the rate-determining step of the rearrangement of allylic N-(p-methoxyphenyl)trifluoroacetimidates is C-N bond formation. This assumption seems valid, because the relative rearrangement rates of allylic N-(p-methoxyphenyl)trifluoroacetimidates with E vs Z olefin geometries mirror those of allylic trichloroacetimidates.
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76
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12344323451
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The importance of the planar chirality of COP catalysts has been previously investigated. See
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The importance of the planar chirality of COP catalysts has been previously investigated. See: Prasad, R. S.; Anderson, C. E.; Richards, C. J.; Overman, L. E. Organometallics 2005, 24, 77-81.
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(2005)
Organometallics
, vol.24
, pp. 77-81
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Prasad, R.S.1
Anderson, C.E.2
Richards, C.J.3
Overman, L.E.4
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77
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(n+1) ions.
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(n+1) ions.
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