Reconstructive Synthesis of Fluorinated Dihydropyrido[1,2‐a] 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 aryl moiety using N‐fluorobenzenesulfonimide (NFSI) in the presence of inorganic carbonates (Cs2CO3 or K2CO3) in methanol at room temperature within one hour. Generated fluorinated keto acid esters bearing ortho‐nitro aryl groups were transformed into fluorinated dihydropyrido[1,2‐a]indolones (DHPIs) via reductive cyclization using B2(OH)4 followed by amidation in the presence of K2CO3. This "cut‐to‐fuse" strategy enables the reconstructive synthesis of valuable fused heterocycles from relatively simple cyclohexadione.