An improved synthesis of 2-substituted-3-furoic acids leading to an intramolecular Diels–Alder reaction between a dienophile and furan diene both containing an electron withdrawing group

An improved preparation of various 2-substituted-3-furoic acids by lithiation of 2-methyl-3-furoic acid with 2.0 equiv. of butyllithium, and a successful intramolecular Diels–Alder reaction using 0.1 equiv. of methylaluminium dichloride between a dienophile and furan diene, which are both substituted with an electron withdrawing moiety, are described.