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Molecules 2013, 18(9), 10901-10911; doi:10.3390/molecules180910901
Article

A Recyclable Palladium-Catalyzed Synthesis of 2-Methylene-2,3-Dihydrobenzofuran-3-ols by Cycloisomerization of 2-(1-Hydroxyprop-2-ynyl)phenols in Ionic Liquids

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Received: 29 July 2013 / Revised: 21 August 2013 / Accepted: 2 September 2013 / Published: 4 September 2013
(This article belongs to the Special Issue Palladium Catalysts)
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Abstract

A recyclable palladium-catalyzed synthesis of 2-methylene-2,3-dihydrobenzofuran-3-ols 2 by heterocyclization of 2-(1-hydroxyprop-2-ynyl)phenols 1 in an ionic liquid medium (BmimBF4) is presented. The process takes place under relatively mild conditions (100 °C, 5 h) in the presence of catalytic amounts (2 mol %) of PdI2 in conjunction with KI (5 equiv with respect to PdI2) and an organic base, such as morpholine (1 equiv with respect to 1), to give 2 in high yields (70%–86%). The PdI2-KI catalytic system could be recycled up to six times without appreciable loss of activity. Moreover, products 2 could be easily converted in a one-pot fashion into 2-hydroxymethylbenzofurans 3 (52%–71%, based on 1) and 2-methoxymethylbenzofurans 4 (52%–80%, based on 1) by acid-catalyzed allylic isomerization or allylic nucleophilic substitution.
Keywords: benzofurans; cycloisomerization; dihydrobenzofurans; ionic liquids; palladium; recyclable synthesis benzofurans; cycloisomerization; dihydrobenzofurans; ionic liquids; palladium; recyclable synthesis
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Mancuso, R.; Gabriele, B. A Recyclable Palladium-Catalyzed Synthesis of 2-Methylene-2,3-Dihydrobenzofuran-3-ols by Cycloisomerization of 2-(1-Hydroxyprop-2-ynyl)phenols in Ionic Liquids. Molecules 2013, 18, 10901-10911.

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