Novel Tunable CuX₂-Mediated Cyclization Reaction of Cyclopropylideneacetic Acids and Esters for the Facile Synthesis of 4-Halomethyl-2(5<i>H</i>)-furanones and 4-Halo-5,6-dihydro-2<i>H</i>-pyran-2-ones

Abstract

[reaction: see text] A mixture of cyclopropylideneacetic acids (or esters) and CuBr(2) (or CuI/I(2)) in aqueous acetonitrile afforded 4-substituted 2(5H)-furanones or 3,4-substituted 5,6-dihydro-2H-pyran-2-ones in moderate to good yields. The selectivity of the reaction greatly depended on the reaction temperature.