Access to Chromenopyrrole via Tandem [3 + 2] Cycloaddition and Intramolecular C–O Coupling

Abstract

A mild and concise method for the synthesis of chromenopyrrole from 2′-hydroxychalcone is devised. The reaction proceeds via an initial [3 + 2] cycloaddition on the C�C bond of 2′-hydroxychalcone and 1,3-dipolarophile, generated in situ by the reaction of ethyl isocyanoacetate and AgOAc. This is then followed by an intramolecular C−O bond formation with the −OH group and C5−H of the in situ generated pyrrole, leading to chromenopyrroles. pyoluteorin, the marinopyrroles, TAN-876A, and TAN-876B. 4a,c Considering the wide utility of chromenopyrroles,