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Volumn 7, Issue 4, 2005, Pages 645-648

One-pot four-component reaction: Aqueous TiCl3/PhN 2+-mediated alkyl radical addition to imines generated in situ

Author keywords

[No Author keywords available]

Indexed keywords

CHLORINE DERIVATIVE; DIAZONIUM COMPOUND; IMINE; IODINE; NITROGEN DERIVATIVE; PHENYL GROUP; TITANIUM DERIVATIVE;

EID: 14844354033     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol047595d     Document Type: Article
Times cited : (40)

References (37)
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  • 4
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    • For reviews on radical addition to C=N bond, see: (a) Miyabe, H.; Ueda, M.; Naito, T. Synlett 2004, 1140-1157. (b) Ishibashi, H.; Sato, T.; Ikeda, M. Synthesis 2002, 695-713. (c) Friestad, G. K. Tetrahedron 2001, 57, 5461-5496. (d) Naito, T. Heteocycles 1999, 50, 505-541.
    • (2004) Synlett , pp. 1140-1157
    • Miyabe, H.1    Ueda, M.2    Naito, T.3
  • 5
    • 0036248015 scopus 로고    scopus 로고
    • For reviews on radical addition to C=N bond, see: (a) Miyabe, H.; Ueda, M.; Naito, T. Synlett 2004, 1140-1157. (b) Ishibashi, H.; Sato, T.; Ikeda, M. Synthesis 2002, 695-713. (c) Friestad, G. K. Tetrahedron 2001, 57, 5461-5496. (d) Naito, T. Heteocycles 1999, 50, 505-541.
    • (2002) Synthesis , pp. 695-713
    • Ishibashi, H.1    Sato, T.2    Ikeda, M.3
  • 6
    • 0035948184 scopus 로고    scopus 로고
    • For reviews on radical addition to C=N bond, see: (a) Miyabe, H.; Ueda, M.; Naito, T. Synlett 2004, 1140-1157. (b) Ishibashi, H.; Sato, T.; Ikeda, M. Synthesis 2002, 695-713. (c) Friestad, G. K. Tetrahedron 2001, 57, 5461-5496. (d) Naito, T. Heteocycles 1999, 50, 505-541.
    • (2001) Tetrahedron , vol.57 , pp. 5461-5496
    • Friestad, G.K.1
  • 7
    • 0032837567 scopus 로고    scopus 로고
    • For reviews on radical addition to C=N bond, see: (a) Miyabe, H.; Ueda, M.; Naito, T. Synlett 2004, 1140-1157. (b) Ishibashi, H.; Sato, T.; Ikeda, M. Synthesis 2002, 695-713. (c) Friestad, G. K. Tetrahedron 2001, 57, 5461-5496. (d) Naito, T. Heteocycles 1999, 50, 505-541.
    • (1999) Heteocycles , vol.50 , pp. 505-541
    • Naito, T.1
  • 9
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    • and references quoted therein
    • (b) Yamada, K.; Yamamoto, Y.; Tomioka, K. Org. Lett. 2003, 5, 1797-1799 and references quoted therein.
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    • Yamada, K.1    Yamamoto, Y.2    Tomioka, K.3
  • 20
    • 0001270538 scopus 로고
    • Ti(IV) is known to promote imine formation. (a) Weingarten, H.; Chupp, J. P.; White, W. A. J. Org. Chem. 1967, 32, 3246-3249. (b) Desai, M. C.; Thadeio, P. F. Tetrahedron Lett. 1989, 30, 5223-5226. In a blank experiment we proved that an aqueous acidic solution of Ti(IV) is much more efficient than an aqueous acidic solution of Ti(III) in promoting imine formation.
    • (1967) J. Org. Chem. , vol.32 , pp. 3246-3249
    • Weingarten, H.1    Chupp, J.P.2    White, W.A.3
  • 21
    • 8544280430 scopus 로고
    • Ti(IV) is known to promote imine formation. (a) Weingarten, H.; Chupp, J. P.; White, W. A. J. Org. Chem. 1967, 32, 3246-3249. (b) Desai, M. C.; Thadeio, P. F. Tetrahedron Lett. 1989, 30, 5223-5226. In a blank experiment we proved that an aqueous acidic solution of Ti(IV) is much more efficient than an aqueous acidic solution of Ti(III) in promoting imine formation.
    • (1989) Tetrahedron Lett. , vol.30 , pp. 5223-5226
    • Desai, M.C.1    Thadeio, P.F.2
  • 23
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    • note
    • +) or as a N-Ti(IV)-complexed imine.
  • 24
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    • +), thus, at pH = 1, the equilibrium aminyl ↔ aminium radical, is by far shifted in favor of the latter. Russel, G. A.; Wang, L.; Rajaratnam, R. J. Org. Chem. 1996, 61, 8988-8991.
    • (1996) J. Org. Chem. , vol.61 , pp. 8988-8991
    • Russel, G.A.1    Wang, L.2    Rajaratnam, R.3
  • 32
    • 0034704336 scopus 로고    scopus 로고
    • The PMP amine protecting group has been also chosen because it can be readily removed upon further CAN-oxidative transformations. Hasegawa, M.; Tanijama, D.; Tomioka, K. Tetrahedron 2000, 36, 10153-10158.
    • (2000) Tetrahedron , vol.36 , pp. 10153-10158
    • Hasegawa, M.1    Tanijama, D.2    Tomioka, K.3
  • 33
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    • note
    • This sensitivity to steric hindrance is in line with a crowded transition state due to Ti(IV) complexation rather than imine protonation
  • 35
    • 14844366360 scopus 로고    scopus 로고
    • note
    • Additional N-alkylation was not observed with the other more volatile and/or less reactive alkyl iodides. In fact, by extracting the reaction mixture with EtOAc prior to neutralization of the aqueous acidic solution, the C-alkylated products were isolated in their protonated form. Further concentration of the organic extracts, at a reduced pressure, allowed elimination of the excess RI, thus hampering the additional N-alkylation, which may occur during further basic workup.


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