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Volumn 73, Issue 18, 2008, Pages 7336-7341

A novel synthesis of 2-functionalized benzofurans by palladium-catalyzed cycloisomerization of 2-(1-hydroxyprop-2-ynyl)phenols followed by acid-catalyzed allylic isomerization or allylic nucleophilic substitution

Author keywords

[No Author keywords available]

Indexed keywords

CHEMICAL REACTIONS; ELECTRON TRANSITIONS; ISOMERIZATION; ISOMERS; PALLADIUM; PHENOLS;

EID: 52449131351     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo801444n     Document Type: Article
Times cited : (60)

References (123)
  • 31
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    • For recent advances in the synthesis of benzofuran derivatives, see: a
    • For recent advances in the synthesis of benzofuran derivatives, see: (a) Sakai, N.; Uchida, N.; Konakahara, T. Tetrahedron Lett. 2008, 49, 3437-3440.
    • (2008) Tetrahedron Lett , vol.49 , pp. 3437-3440
    • Sakai, N.1    Uchida, N.2    Konakahara, T.3
  • 49
    • 33846157728 scopus 로고    scopus 로고
    • (s) Zhao, B.; Lu, X. Org. Lett. 2006, 8, 5987-5990.
    • (2006) Org. Lett , vol.8 , pp. 5987-5990
    • Zhao, B.1    Lu, X.2
  • 83
    • 46849092817 scopus 로고    scopus 로고
    • We have recently shown that PdI2 in conjunction with an excess of KI is an excellent catalyst for the heterocyclization of several acetylenic substrates bearing a suitably placed nucleophilic group. See ref 2r, ii, yy and: (a) Gabriele, B, Mancuso, R, Salerno, G, Lupinacci, E, Ruffolo, G, Costa, M. J. Org. Chem. 2008, 73, 4971-4977
    • We have recently shown that PdI2 in conjunction with an excess of KI is an excellent catalyst for the heterocyclization of several acetylenic substrates bearing a suitably placed nucleophilic group. See ref 2r, ii, yy and: (a) Gabriele, B.; Mancuso, R.; Salerno, G.; Lupinacci, E.; Ruffolo, G.; Costa, M. J. Org. Chem. 2008, 73, 4971-4977.
  • 120
    • 52449097925 scopus 로고    scopus 로고
    • The methodology could not be applied to alcohols of low nucleophilicity, such as isopropyl alcohol (R = i-Pr) or tert-butylalcohol (R = t-Bu), or to phenols (R = Ar); in these cases, the GLC, GLC-MS, and TLC analyses of the reaction crudes showed that substrates 2 preferentially underwent decomposition, with formation of small amounts of the desired products, which, however, owing to the complexity of the mixture, could not be isolated at the pure state.
    • The methodology could not be applied to alcohols of low nucleophilicity, such as isopropyl alcohol (R = i-Pr) or tert-butylalcohol (R = t-Bu), or to phenols (R = Ar); in these cases, the GLC, GLC-MS, and TLC analyses of the reaction crudes showed that substrates 2 preferentially underwent decomposition, with formation of small amounts of the desired products, which, however, owing to the complexity of the mixture, could not be isolated at the pure state.
  • 121
    • 0001088331 scopus 로고    scopus 로고
    • 2-promoted deprotection of the corresponding methylthiomethyl ether) by classical intramolecular conjugate addition to give a mixture of (3-hydroxy-3-methyl-3H-benzofuran-2-ylidene) acetic acid ethyl ester (15%) and hydroxy-(3-methylbenzofuran-2-yl)acetic acid ethyl ester (68%) was reported some years ago. Pflieger, D.; Muckensturm, B. Tetrahedron 1989, 45, 2031-2040.
    • 2-promoted deprotection of the corresponding methylthiomethyl ether) by classical intramolecular conjugate addition to give a mixture of (3-hydroxy-3-methyl-3H-benzofuran-2-ylidene) acetic acid ethyl ester (15%) and hydroxy-(3-methylbenzofuran-2-yl)acetic acid ethyl ester (68%) was reported some years ago. Pflieger, D.; Muckensturm, B. Tetrahedron 1989, 45, 2031-2040.
  • 122
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    • +], 161 (13), 160 (87), 145 (7), 132 (21), 118 (16), 117 (41), 103 (30), 102 (43), 89 (100), 77 (22), 63 (59), 62 (23), 53 (33), 51 (22).
    • +], 161 (13), 160 (87), 145 (7), 132 (21), 118 (16), 117 (41), 103 (30), 102 (43), 89 (100), 77 (22), 63 (59), 62 (23), 53 (33), 51 (22).


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