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Volumn , Issue 20, 2006, Pages 3467-3477

Synthesis of indoles: Efficient functionalisation of the 7-position

Author keywords

2 vinylanilines; Heck reaction; Indoles; Larock's cyclisation; Palladium

Indexed keywords

ACETYLENE; CHEMICAL MODIFICATION; SUBSTITUTION REACTIONS; SYNTHESIS (CHEMICAL);

EID: 33750598471     PISSN: 00397881     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-2006-950223     Document Type: Article
Times cited : (27)

References (61)
  • 2
    • 33750600956 scopus 로고    scopus 로고
    • note
    • A search for the indole core in the WDI database retrieved more than 3700 hits. See also ref. 12a.
  • 9
    • 84990086006 scopus 로고
    • For a review on the Use of transition metals in the synthesis and functionalisation of indoles, see: (a) Hegedus, L. S. Angew. Chem., Int. Ed. Engl. 1988, 27, 1113.
    • (1988) Angew. Chem., Int. Ed. Engl. , vol.27 , pp. 1113
    • Hegedus, L.S.1
  • 10
    • 22944454156 scopus 로고    scopus 로고
    • For a recent and very well-documented review on the synthesis of indoles through palladium-catalysed reactions, see: (b) Cacchi, S.; Fabrizi, G. Chem. Rev. 2005, 105, 2873.
    • (2005) Chem. Rev. , vol.105 , pp. 2873
    • Cacchi, S.1    Fabrizi, G.2
  • 15
    • 17444414639 scopus 로고    scopus 로고
    • see also ref. 7b
    • This list is not exhaustive. For example, since the completion of this work, a one-pot synthesis of indoles via enamines has been reported, see: Barluenga, J.; Fernandez, M. A.; Aznar, F.; Valdes, C. Chem. Eur. J. 2005, 11, 2276; see also ref. 7b.
    • (2005) Chem. Eur. J. , vol.11 , pp. 2276
    • Barluenga, J.1    Fernandez, M.A.2    Aznar, F.3    Valdes, C.4
  • 19
    • 0026769043 scopus 로고
    • It is possible to functionalise the 3-position in situ, but it needs concomitant substitution at the 2-position: (a) Arcadi, A.; Cacchi, S.; Marinelli, F. Tetrahedron Lett. 1992, 33, 3915.
    • (1992) Tetrahedron Lett. , vol.33 , pp. 3915
    • Arcadi, A.1    Cacchi, S.2    Marinelli, F.3
  • 32
    • 33750600955 scopus 로고    scopus 로고
    • note
    • The synthesis of the 7-substituted indoles will be described with ethyl or n-propyl at the 3-position. The synthetic routes described in this paper are applicable to both substituents.
  • 37
    • 0000629440 scopus 로고    scopus 로고
    • Liebeskind, L. S., Ed.; JAI Press: Greenwich CT
    • (d) Jeffery, T. In Advances in Metal-Organic Chemistry, Vol. 5; Liebeskind, L. S., Ed.; JAI Press: Greenwich CT, 1996, 153-260.
    • (1996) Advances in Metal-Organic Chemistry , vol.5 , pp. 153-260
    • Jeffery, T.1
  • 40
    • 85083010444 scopus 로고
    • For a review on iodination of aryl compounds, see: Merkushev, E. B. Synthesis 1988, 923.
    • (1988) Synthesis , pp. 923
    • Merkushev, E.B.1
  • 41
    • 3142720289 scopus 로고    scopus 로고
    • This side reaction is not observed with 2-nitro aniline: Ragagnin, G.; Knochel, P. Synlett 2004, 951.
    • (2004) Synlett , pp. 951
    • Ragagnin, G.1    Knochel, P.2
  • 45
    • 33750576285 scopus 로고    scopus 로고
    • note
    • An NOE experiment proved that the stereochemistry of the exocyclic double bond is as shown in Scheme 7.
  • 48
    • 33750591724 scopus 로고    scopus 로고
    • note
    • See references 133d and 136a-e cited in ref. 7b.
  • 49
    • 33750588200 scopus 로고    scopus 로고
    • note
    • Compounds 28a and 28b are drawn as acids for convenience, but are isolated as trimers. See ref. 20a.
  • 54
    • 85083276516 scopus 로고
    • The synthesis of indoles from 2-halogenated anilines and a (2-alkoxyvinyl)boronic ester, followed by hydrolysis and in situ cyclisation has also been described. However, the synthesis of the (2-alkoxyvinyl)boronic ester requires two steps and we felt this route would not offer significant advantages compared to the others (see below): Satoh, M.; Miyaura, N.; Suzuki, A. Synthesis 1987, 373.
    • (1987) Synthesis , pp. 373
    • Satoh, M.1    Miyaura, N.2    Suzuki, A.3
  • 55
    • 33750586086 scopus 로고    scopus 로고
    • note
    • The structure of 30 was assigned by an NOE experiment.
  • 56
    • 33750578288 scopus 로고    scopus 로고
    • note
    • We ensured that we were able to reproduce Larock's results on 2-iodoaniline. Under the same conditions, methyl 4-amino-3-iodo-benzoate gave a 94:6 mixture of isomers. Within this set of examples, the selectivity appears related to the electron deficiency of the aromatic ring.
  • 57
    • 33750594485 scopus 로고    scopus 로고
    • note
    • We did not attempt to increase the yield of the ring formation by using substituents more stable than trimethylsilyl to the reaction conditions, since the yield obtained was adequate for our purposes.
  • 58
    • 33750578137 scopus 로고    scopus 로고
    • note
    • Removal of the trifluoroacetamido group proved easier for 25 (deprotection takes 45 minutes at room temperature) than for 14 (deprotection not complete after two days under similar conditions).


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.