Abstract Methyl 3-formylcyclobutene-3-carboxylate was synthesized in five steps from commercially available cyclobutane-1, 1-dicarboxylic acid. Thermolysis afforded methyl (2H)- pyrane-5-carboxylate, which was formed by electrocyclization of the formyl-in, ester-out product of ring opening. This confirms theoretical predictions.
