4-Hydroxy-2-butenolide. A Versatile Reagent for the Synthesis of Heterocyclic Compounds

Article abstract of DOI:10.1021/jo00140a015

The base-catalyzed reaction of hydroxy lactone 1 with several cyclic and acyclic vinylogous amides and 1,3-dicarbonyl compounds was found to provide a smooth method to prepare pyrrole, furan, tetrahydroindole, and tetrahydrobenzofuran ring systems.The reaction of 1 with the cyclic enaminone 2 affords 3 which can be isomerized to the tetrahydroindole-2-acetic acid 4.The reaction of 1 with 6 and 8 produces, after esterification, the methyl tetrahydroindole-and pyrrole-2-acetates 7a and 9a, respestively.With acyclic 1,3-dicarbonyl compounds, 1 reacts to give furan-2-acetic acids, whereas the reaction of 1 with cyclic β-diketones leads to furo<3,2-b>benzofuran derivatives.The latter can be easily isomerized by heating with diluted acid to the corresponding tetrahydrobenzofuran-2-acetic acids.A possible mechanism for these reactions is proposed.