Palladium(II)-Catalyzed Oxidative Transformation of Allylic Alcohols and Vinyl Ethers into 2-Alkoxytetrahydrofurans:  Catechol as an Activator of Catalyst

<UFIGR ID="ol052377ln00001">A highly effective synthesis of 2-alkoxytetrahydrofurans from allylic alcohols and vinyl ethers was achieved by using catalytic amounts of Pd(OAc)<INF>2</INF>, Cu(OAc)<INF>2</INF>, and catechol (1:1:2) under O<INF>2</INF>. The use of catechol as an activator of Pd(II)−Cu(II) catalyst has been unprecedented. The 2-alkoxytetrahydrofurans are formed via oxypalladation of allylic alcohols toward vinyl ethers followed by 5-exo cyclization of the resulting oxypalladation intermediate and subsequent β-Pd−H elimination. No 6-endo cyclization of the oxypalladation intermediate occurs.