Thermal rearrangement of 4-cyano-2,3-dihydro-5-ethoxy-3-methyl-3-(4-oxo-4H-1- benzopyran-3-yl)furans: a reversed alkoxycarbonylcyclopropane → 5-alkoxy-2,3-dihydrofuran transformation
Abstract
The title dihydrofurans (3f, R1= H, Me, and Cl), prepared from the α-cyano-ester (1e) and diazomethane, thermally rearrange to the cyclopropanes (4f) in predominantly Z-isomeric form.