title: 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.
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.
authors.affiliation: Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, Ponte Pietro Bucci 12/C, Arcavacata di Rende (CS) 87036, Italy. raffaella.mancuso@unical.it
authors.forename: Raffaella
authors.initials: R
authors.lastname: Mancuso
authors.forename: Bartolo
authors.initials: B
authors.lastname: Gabriele
mesh_terms: D001572:Benzofurans / Q000138:chemical synthesis*; D002384:Catalysis; D003500:Cyclization; D055772:Green Chemistry Technology; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry; D010165:Palladium / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: C419324:1-butyl-3-methylimidazolium tetrafluoroborate; D001572:Benzofurans; D007093:Imidazoles; D052578:Ionic Liquids; D010636:Phenols; D010165:Palladium