Reconstructive Synthesis of Fluorinated Dihydropyrido[1,2‐<i>a</i>] indolones by a Cyclohexadione Cut‐to‐Fuse Strategy

Abstract We describe a fluorinative ring‐cleavage reaction that breaks C−C bonds in cyclic β‐diketones bearing an aryl moiety by using N ‐fluorobenzenesulfonimide (NFSI) in the presence of inorganic carbonates (Cs 2 CO 3 or K 2 CO 3 ) in methanol at room temperature within one hour. The generated fluorinated keto acid esters bearing ortho ‐nitro aryl groups were transformed into fluorinated dihydropyrido[1,2‐ a ]indolones (DHPIs) via reductive cyclization using B 2 (OH) 4 followed by amidation in the presence of K 2 CO 3 . This “cut‐to‐fuse” strategy enables the reconstructive synthesis of valuable fused heterocycles from relatively simple cyclohexadiones.