Access to the Phosphorylindenopyrazole Scaffold via a Metal-Free Domino Reaction of Diazoalkylphosphonates with 3‑Bromophthalides

A novel strategy is reported here for the synthesis of an indenopyrazole scaffold bearing a phosphonate group. The entire sequence includes nucleophilic addition–elimination, Seyferth–Gilbert homologation, transphosphorylation, and a 1,3-dipolar cycloaddition reaction of diazoalkylphosphonates in a perfect “domino” manner.