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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

*  and *
Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Ponte Pietro Bucci 12/C, Arcavacata di Rende (CS) 87036, Italy
* Authors to whom correspondence should be addressed.
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 (CC BY 3.0).
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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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