Abstract
Ligand-exchange reactions of manganese (III) acetate with 1, 3-dicarbonyl compounds were found to occur in situ in acetic acid with consequent formation of new manganese (III) -enolate complexes. Manganese (III) -enolate complexes were reacted with alkenes in acetic acid at over 100°C to produce the corresponding carbon radicals which were then oxidized with manganese (III) followed by intramolecular cyclization to produce 4, 5-dihydrofurans. Reactions of α, ω-alkadienes with malonic acid or malonamide resulted in inter- and intra-molecular cyclization to afford bicyclic and/or tricyclic lactones and/or lactams. Manganese (III) -based oxidation of oligomethylene di (3-oxobutanoate) s with α, ω-alkadienes gave macrodiolides, each possessing two fused dihydrofuran rings, in good yields. The macrocyclic compounds were shown to have the capacity to incorporate alkali metal ions. Similar reactions of manganese (III) -enolate complexes with alkenes at 23°C in air slowly produced similar carbon radicals. Molecular oxygen was trapped in the reaction mixture with carbon radicals to produce peroxyl radicals which subsequently underwent reduction by manganese (II) and cyclization to quantitatively yield 1, 2-dioxan-3-ols. Using pyrrolidinedione and piperidone derivatives in reaction at 23°C provided azabicyclic peroxides. Acid-catalyzed decomposition of 1, 2-dioxan-3-ols yielded the corresponding functionalized furans, while palladium-catalyzed hydrogenolysis of azabicyclic peroxides led to extrusion of one peroxide oxygen to give tetrahydrofuran derivatives. Manganese (III) -based oxidation of alkenes with 1, 3-dicarbonyl compounds may thus be concluded an effective means for organic synthesis
