Abstract

During the research on the Pd-catalyzed intramolecular cyclization reaction via C-H activation, the dehalogenation of 3-halo-2(5H)-furanones is unexpectedly discovered. Under the optimized conditions without any special anaerobic and anhydrous treatments, using N,N-diisopropylethylamine (DIPEA) simultaneously as hydrogen source and base, the reactions of 27 substrates with less Pd catalyst (5 mol% Pd(PPh₃)₄) usually give higher yields (70-99%, mostly over 82%). Especially for 3-halo-2(5H)-furanone substrates simultaneously containing aryl halide structure, this kind of Pd-catalyzed dehalogenation has good selectivity. After the selectivity is explained via the substrate theoretical calculation, a possible reaction mechanism of the Pd-catalyzed dehalogenation is proposed. These novel investigations provide an efficient, simple, practical and selective Pd-catalyzed dehalogenation method for the non-aromatic halide substrates with many different functional groups.

Keywords: Amines, chemoselectivity, dehalogenation, 2(5H)-Furanone, halide, mass spectroscopy, palladium.