Influence of Lewis Acids on the Diels–Alder Reaction. VII. The Reaction of Furan with Ethyl Propiolate

Abstract

Reaction of furan and ethyl propiolate at 130° affords a low yield of 2,6-dicarbethoxy-9-oxatetracyclo[3.2.1.1.3,802,4]non-6-ene (4). This structure was confirmed by 1H and 13C n.m.r. spectroscopy. In the presence of AlCl3 the same addends give only a mixture of the Diels–Alder endo–endo10 and endo–exo11 diadducts. Isomer 11 is decomposed by AlCl3, the rate of decomposition, and therefore the product ratio 10:11, being as expected dependent on time, temperature, and reactant concentrations.