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Enders, D.1
Breuer, K.2
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Teles, J.H.4
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10
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22144480983
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For the syntheses of triazolium salts, see
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For the syntheses of triazolium salts, see: Kerr, M. S.; Read de Alaniz, J.; Rovis, T. J. Org. Chem. 2005, 70, 5725-5728.
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Kerr, M.S.1
Read de Alaniz, J.2
Rovis, T.3
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For other contributions, see: a
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For other contributions, see: (a) Pesch, J.; Harms, K.; Bach, T. Eur. J. Org. Chem. 2004, 2025-2035.
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Pesch, J.1
Harms, K.2
Bach, T.3
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12
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12744273171
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(b) Mennen, S. M.; Blank, J. T.; Tran-Dube, M. B.; Imbriglio, J. E.; Miller, S. J. Chem. Commun. 2005, 195-197.
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Mennen, S.M.1
Blank, J.T.2
Tran-Dube, M.B.3
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Miller, S.J.5
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54849432201
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Liu, Q.; Perreault, S.; Rovis, T. J. Am. Chem. Soc. 2008, 130, 14066-14067.
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Liu, Q.1
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Rovis, T.3
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19
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0036089366
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For a review, see
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(a) For a review, see Berner, O. M.; Tedeschi, L.; Enders, D. Eur. J. Org. Chem. 2002, 1877-1894.
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Berner, O.M.1
Tedeschi, L.2
Enders, D.3
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21
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33646146207
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Scheidt has reported a single example of the asymmetric conjugate addition of a stoichiometrically generated acyl anion equivalent to nitroalkenes mediated by a thiourea; see: Mattson, A. E, Zuhl, A. M, Reynolds, T. E, Scheidt, K. A. J. Am. Chem. Soc. 2006, 128, 4932-4933
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Scheidt has reported a single example of the asymmetric conjugate addition of a stoichiometrically generated acyl anion equivalent to nitroalkenes mediated by a thiourea; see: Mattson, A. E.; Zuhl, A. M.; Reynolds, T. E.; Scheidt, K. A. J. Am. Chem. Soc. 2006, 128, 4932-4933.
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23
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68249159091
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Other solvents: PhMe (trace), THF (trace), EtOH (59%, 70% ee).
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Other solvents: PhMe (trace), THF (trace), EtOH (59%, 70% ee).
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24
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0030457120
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Eberhardt, E. S.; Panasik, N., Jr.; Raines, R. T. J. Am. Chem. Soc. 1996, 118, 12261-12266.
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Eberhardt, E.S.1
Panasik Jr., N.2
Raines, R.T.3
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25
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28044458136
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2-symmetric difluoro-pyrrolidine derivative has been shown to be a moderately effective ligand in the asymmetric epoxidation of an allylic alcohol: Marson, C. M.; Melling, R. C. J. Org. Chem. 2005, 70, 9771-9779.
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2-symmetric difluoro-pyrrolidine derivative has been shown to be a moderately effective ligand in the asymmetric epoxidation of an allylic alcohol: Marson, C. M.; Melling, R. C. J. Org. Chem. 2005, 70, 9771-9779.
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26
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44349084146
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4-Fluoroproline has been demonstrated to provide improved selectivities in transannular aldols. Chandler, C. L.; List, B. J. Am. Chem. Soc. 2008, 130, 6737-6739.
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(b) 4-Fluoroproline has been demonstrated to provide improved selectivities in transannular aldols. Chandler, C. L.; List, B. J. Am. Chem. Soc. 2008, 130, 6737-6739.
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27
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70349783652
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It has recently been argued that a fluorine substituent improves iminium ion geometry in asymmetric epoxidation of unsaturated aldehydes. Sparr, C, Schweizer, W. B, Senn, H. M, Gilmour, R. Angew. Chem, Int. Ed. 2009, 48, 3065-3068
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(c) It has recently been argued that a fluorine substituent improves iminium ion geometry in asymmetric epoxidation of unsaturated aldehydes. Sparr, C.; Schweizer, W. B.; Senn, H. M.; Gilmour, R. Angew. Chem., Int. Ed. 2009, 48, 3065-3068.
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28
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68249137793
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We are aware of the caveats associated with solid-state analysis of a precatalyst; however, these arguments are self-consistent and rationalize the observed results
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We are aware of the caveats associated with solid-state analysis of a precatalyst; however, these arguments are self-consistent and rationalize the observed results.
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31
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68249152895
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Another hyperconjugative effect that cannot be ruled out is a π to σ*C-F interaction. Schaefer et al. reported that fluorine in benzyl fluorides adopts a perpendicular arrangement with respect to the aromatic ring, due to π donation of the aromatic ring into the low lying σ*C-F. A similar effect can be rationalized for our system where hyperconjugation can only occur from the observed Cγ-exo ring pucker. We believe this is unlikely due to the developing positive charge in the azolium ring occurring in the transition state of the C-C bond-forming event but may play a small role. See: Schaefer, T, Schurko, R. W, Sebastian, R, Hruska, F. E. Can. J. Chem. 1995, 73, 816-825
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C-F. A similar effect can be rationalized for our system where hyperconjugation can only occur from the observed Cγ-exo ring pucker. We believe this is unlikely due to the developing positive charge in the azolium ring occurring in the transition state of the C-C bond-forming event but may play a small role. See: Schaefer, T.; Schurko, R. W.; Sebastian, R.; Hruska, F. E. Can. J. Chem. 1995, 73, 816-825.
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68249139362
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Benzaldehyde fails to participate under these conditions. The reasons for this are the subject of investigation in our laboratory. Evidence suggests that the role of the heteroatom is not simply that of a proximal Lewis base given that both pyridazine carboxaldehyde and furfural participate with equal facility in spite of their very low basicity
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Benzaldehyde fails to participate under these conditions. The reasons for this are the subject of investigation in our laboratory. Evidence suggests that the role of the heteroatom is not simply that of a proximal Lewis base given that both pyridazine carboxaldehyde and furfural participate with equal facility in spite of their very low basicity.
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33
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68249160253
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Numerical comparison of ee values is problematic. Comparison of er values can be equally problematic. For example, 3d is formed in 98:2 er with 8 and 93:7 er with 6, an apparent difference of 5 er points. However, a more instructive comparison here would be 13:1 vs 49:1 for 3d.
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Numerical comparison of ee values is problematic. Comparison of er values can be equally problematic. For example, 3d is formed in 98:2 er with 8 and 93:7 er with 6, an apparent difference of 5 er points. However, a more instructive comparison here would be 13:1 vs 49:1 for 3d.
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34
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Böhm, H. J.; Banner, D.; Bendels, S.; Kansy, M.; Kuhn, B.; Müller, K.; Obst-Sander, U.; Stahl, M. ChemBioChem 2004, 5, 637-643.
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, pp. 637-643
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Böhm, H.J.1
Banner, D.2
Bendels, S.3
Kansy, M.4
Kuhn, B.5
Müller, K.6
Obst-Sander, U.7
Stahl, M.8
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