Synthesis of Chromenopyrroles (Azacoumestans) from Functionalized Enones and Alkyl Isocyanoacetates

Elegant synthetic strategies for chromenopyrroles (azacoumestans) have been devised via cycloaddition of 2-hydroxychalcone/cyclic enones and alkyl isocyanoacetate, followed by lactonization. Herein, ethyl isocyanoacetate acts as a C–NH–C–CO synthon contrary to its hitherto applications as a C–NH–C synthon. Subsequently, pentacyclic-fused pyrroles were also constructed from the o-iodo benzoyl chromenopyrroles using the Pd­(II) catalyst.