Dehalogenation of 3-halide-2(5H)-furanones in the absence of Pd catalyst

During the studies on the Pd-catalyzed dehalogenation reaction, it was accidentally found that the dehalogenation reaction of 3-halo-2(5H)-furanone also could occur even without any Pd catalysts. Under the optimized reaction conditions, such as base 12 equiv. Et3N, solvent CH3CN, and reaction temperature 150 °C, the best yield can be 52%. For the substrates simultaneously containing aryl halide structure, this Pd-catalyst-free dehalogenation reaction has good selectivity. The combination of this unique selectivity with the Pd-catalyzed dehalogenation reaction can provide many control choices for the selective dehalogenation of the non-aromatic halide substrates with many different functional groups, especially varied halogen atoms. The studies on the reaction mechanism by D2O experiments show that triethylamine is used as not only organic base, but also the hydrogen source of dehalogenation reaction. However, it is difficult to completely remove the possibility of water as a hydrogen source in this reaction.