2 + 2 Cycloadditions of Benzofuran-3(2H)-one Enamines With Dimethyl Acetylenedicarboxylate

摘要

2 + 2Cycloaddition reactions have been used for the ring expansion by two-carbon atoms. The reactions of enamines derived from cyclic ketones with activated acetylenes via cycloadditions involve the formation of fused cyclobutene adducts which may then undergo thermal isomerization to yield two carbons-enlarged rearrangement products.