Cascade Reactions: Catalytic Synthesis of Functionalized 1,3-Dihydroisobenzofuran and Tetrahydrofuran Derivatives by Sequential Nucleophilic Ring Opening-Heterocyclization-Oxidative Carbonylation of Alkynyloxiranes

Differently substituted alkynyloxiranes were efficiently converted into functionalized 1,3-dihydroisobenzofurans and tetrahydrofuran derivatives in fair to good yields by a new cascade reaction, consisting of a sequential nucleophilic ring opening–heterocyclization– oxidative carbonylation process. Reactions were carried out at 80–100 8C and under a 3:1 mixture of carbon monoxide and air (total pressure= 32–42 atm at 25 8C) in methanol or acetonitrile/ methanol mixtures in the presence of catalytic amounts of palladium diiodide in conjunction with an excess of potassium iodide. The nucleophilic species beginning the cascade process by regioselective attack to the less hindered carbon of the oxirane ring can be methanol itself or iodide anions.