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.

TLDR: The title dihydrofurans (3f, R1= H, Me, and Cl) as discussed by the authors is derived from the α-cyano-ester (1e) and diazomethane, which thermally rearrange to cyclopropanes (4f) in predominantly Z-isomeric form.

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.