Reconstructive synthesis of fluorinated dihydropyrido[1,2-a]indolones by a cyclohexadione cut-to-fuse strategy

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.