A novel cyclodehydration. Thermal conversion of diethyl 2-naphthoxyoxalacetate to diethyl naphtho[2,1-b]furan-1,2-dicarboxylate
Diethyl 2-naphthoxyoxalacetate, when heated at 205°, did not undergo the expected decarbonylation to give diethyl 2-naphthoxymalonate, but instead cyclised to yield diethyl naphtho[2,1–b]furan-1,2-dicarboxylate. The same cyclisation was effected in acetic acid–sulphuric acid and with toluene-p-sulphonic acid in toluene.
Diethyl 2-naphthoxymalonate was prepared from sodium 2-naphthoxide and diethyl chloromalonate. The reaction of sodium 2-naphthoxide with diethyl bromomalonate afforded diethyl 2-naphthoxymalonate and diethyl bis-(2-naphthoxy)malonate (V), both in poor yields.