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 -iodo benzoyl chromenopyrroles using the Pd(II) catalyst.