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

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.