Furan oxidation by Mn(iii)/Co(ii) catalysts - application to benzofuran synthesis

Furans containing a beta-ketoester group at 2-position undergo oxidative ring-opening by Mn(iii)/Co(ii) catalysts under an O-2 atmosphere to produce 1,4-dicarbonyl moieties through an endoperoxide intermediate, which consecutively cyclized with the beta-ketoester unit to afford 4-hydroxy-2-cyclohexen-1-ones. This oxidation/cyclization products were efficiently transformed into versatile benzofuran derivatives after consecutive aromatization and Paal-Knorr reaction.