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Volumn 127, Issue 38, 2005, Pages 13419-13427

Lewis acid-Lewis acid heterobimetallic cooperative catalysis: Mechanistic studies and application in enantioselective Aza-Michael reaction

Author keywords

[No Author keywords available]

Indexed keywords

AMINO ACIDS; BIMETALS; CATALYSIS; COORDINATION REACTIONS; RARE EARTH ELEMENTS;

EID: 25444512653     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja054066b     Document Type: Article
Times cited : (165)

References (69)
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    • Review for combined acid catalysis including Lewis acid-assisted Lewis acid catalysis, see: (a) Yamamoto, H.; Futatsugi, K. Angew. Chem., Int. Ed. 2005, 44, 1924.
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    • and references therein
    • For representative examples of Lewis acid-assisted Lewis acid catalysis, see: (b) Ishihara, K.; Kobayashi, J.; Inanaga, K.; Yamamoto, H. Synlett 2001, 394 and references therein.
    • (2001) Synlett , pp. 394
    • Ishihara, K.1    Kobayashi, J.2    Inanaga, K.3    Yamamoto, H.4
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    • Reviews for enantioselective conjugate addition: (a) Sibi, M. P.; Manyem, S. Tetrahedron 2000, 56, 8033.
    • (2000) Tetrahedron , vol.56 , pp. 8033
    • Sibi, M.P.1    Manyem, S.2
  • 28
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    • and references therein
    • For recent highly enantioselective catalytic asymmetric 1,4-additions of other nitrogen nucleophiles to afford β-amino carbonyl compounds, see: N-Benzylhydroxylamine: (a) Sibi, M. P.; Prabagaran, N.; Ghorpade, S. G.; Jasperse, C. P. J. Am. Chem. Soc. 2003, 125, 11796 and references therein.
    • (2003) J. Am. Chem. Soc. , vol.125 , pp. 11796
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  • 38
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    • A part of this article (addition to enones, section A) was reported previously as a preliminary communication. Yamagiwa, N.; Matsunaga, S.; Shibasaki, M. J. Am. Chem. Soc. 2003, 125, 16178.
    • (2003) J. Am. Chem. Soc. , vol.125 , pp. 16178
    • Yamagiwa, N.1    Matsunaga, S.2    Shibasaki, M.3
  • 39
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    • note
    • 2O are also discussed in detail in section D.
  • 40
    • 14944386585 scopus 로고    scopus 로고
    • 2O complex was essential to achieve good reactivity and enantioselectivity. Anhydrous YLB 1a complex gave cyanation adducts in poor ee; see: (a) Yamagiwa, N.; Tian, J.; Matsunaga, S.; Shibasaki, M. J. Am. Chem. Soc. 2005, 127, 3413.
    • (2005) J. Am. Chem. Soc. , vol.127 , pp. 3413
    • Yamagiwa, N.1    Tian, J.2    Matsunaga, S.3    Shibasaki, M.4
  • 46
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    • note
    • Ability of Drierite as desiccant toward THF was checked by Karl Fisher experiment. See Supporting Information. Absorption of methoxylamine 3a to molecular sieves was confirmed by NMR analysis of methoxylamine solution in THF using 2,4,6-trimethylbenzene as an internal standard.
  • 47
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    • note
    • 1 = alkyl) are not suitable substrates for the present system. For example, no reaction proceeded with benzalacetone.
  • 51
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    • Properties of N-acylpyrroles and carbonyl dipyrrole 5 were reported by Evans and co-workers in detail. (a) Evans, D. A.; Borg, G.; Scheidt, K. A. Angew. Chem., Int. Ed. 2002, 41, 3188.
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    • Evans, D.A.1    Borg, G.2    Scheidt, K.A.3
  • 55
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    • note
    • Similar tendency that β-aryl substituted carboxylic acid derivatives are much less reactive than β-alkyl substrates was observed in asymmetric aza-Michael reactions of alkoxylamines. See ref 7a and 7b. Trials to activate substrates by introducing an electron-withdrawing group on a pyrrole ring failed.
  • 56
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    • 4 and amine, see: Bongini, A.; Cardillo, G.; Gentilucci, L.; Tomasini, C. J. Org. Chem. 1997, 62, 9148. For the use of NaOt-Bu, see ref 7d. No loss of enantiomeric excess was observed during transformations in Scheme 1 as confirmed by HPLC analysis.
    • (1997) J. Org. Chem. , vol.62 , pp. 9148
    • Amine, S.1    Bongini, A.2    Cardillo, G.3    Gentilucci, L.4    Tomasini, C.5
  • 58
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    • Active species of the aza-Michael reaction was proved to have three BINOL units through preliminary kinetic studies. In the preliminary mechanistic studies, however, the reaction mode (Lewis acid-assisted Lewis acid) and coordination mode of substrates remained unclear; Yamagiwa, N.; Matsunaga, S.; Shibasaki, M. Angew. Chem., Int. Ed. 2004, 43, 4493.
    • (2004) Angew. Chem., Int. Ed. , vol.43 , pp. 4493
    • Yamagiwa, N.1    Matsunaga, S.2    Shibasaki, M.3
  • 59
    • 25444484560 scopus 로고    scopus 로고
    • note
    • For the full details of NMR analysis of YLB-3a complex, including YLB 1a region, see Supporting Information.
  • 60
    • 25444490274 scopus 로고    scopus 로고
    • note
    • The tendency observed in Table 5, entries 1-3 is different from results obtained by Inanaga and co-workers using Sc chiral Lewis acid catalysis. In their report, sterically crowded amine 3c gave the best enantioselectivity. See ref 7d.
  • 61
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    • note
    • The irreversibility of the present aza-Michael reaction was experimentally confirmed. See Supporting Information for detail results.
  • 63
    • 25444471969 scopus 로고    scopus 로고
    • note
    • 2O as the seventh ligand are reported. See refs 2, 12 and references therein.
  • 66
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    • For a review discussing kinetic aspects of nonlinear effects, see: (c) Blackmond, D. G. Acc. Chem. Res. 2000, 33, 402.
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  • 68
    • 25444453357 scopus 로고    scopus 로고
    • note
    • Conformationally rigid enones 4x, 4y, 4z and cyclohexenone were used. 4x and 4y with s-cis form afforded aza-Michael products in high ee, although the reactivity was low probably due to steric hindrance. Reaction did not proceed at all with cyclohexenone and enone 4z with s-trans form. Thus, we speculate the reaction would proceed through s-cis conformation. (Diagram presented) 5% yield 20% yield, dr = 1/1 84% ee 93% ee (one isomer) no reaction no reaction
  • 69
    • 25444449146 scopus 로고    scopus 로고
    • note
    • The possibility that amine 3a coordinates to the yttrium center and enone 2a coordinates to Li cannot be excluded completely. Considering the absolute configuration of aza-Michael products, however, we believe the transition state model in Figure 14 is more appropriate.


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