La(OTf)₃‑CatalyzedBenzannulationof 2‑Arylidene‑1<i>H</i>‑indene-1,3(2<i>H</i>)‑diones with Enamino Esters: Direct Access to FunctionalizedFluorenone Derivatives

An attractive method for the preparation of functional fluorenone derivatives has been developed via La(OTf)₃-catalyzed benzannulation of 2-arylidene-1<i>H</i>-indene-1,3(2<i>H</i>)-diones with enamino esters. The reaction involves Michael addition, intramolecular cyclization, dehydration, and aromatization in a one-step process and affords a wide range of functional fluorenone derivatives in moderate to good yields. Moreover, this protocol provides several advantages, including broad substrate scope, readily available materials, high atom economy, and applicability for large-scale synthesis.