Intramolecular Diels–Alder Cycloaddition of Furan-Derived β-Enamino Diketones: An Entry to Diastereoselective Synthesis of Polycyclic Pyrano[3,2-c]quinolin-5-one Derivatives

Abstract

A series of 1,3-cyclodiketone- and tetrahydroepoxyisoindole-fused β-enamino dicarbonyl heterocycles were synthesized via a 1,4-diazabicyclo[2.2.2]octane-catalyzed, CH3NO2-mediated three-component reaction of 1,3-cyclodiketone, furfural, and allylamine in toluene. The target compounds were generated via the formation of β-enamino diketone as a key intermediate, followed by intramolecular Diels-Alder cycloaddition. The prepared molecules bearing a quinoline-2,4-dione moiety could be further brominated with N-bromosuccinimide and diastereoselectively reduced by NaBH4 to afford pyrano[3,2-c]quinolin-5-one-derived heterocycles with six vicinal stereogenic centers.