Mizoroki-Heck carbon-carbon cross-coupling reactions by water-soluble palladium (II) complexes in neat water

Abstract

Water-soluble palladium complexes were synthesized, characterized, tested as (pre)catalyst for Mizoroki-Heck carbon-carbon cross-coupling reactions in water. Cross-coupling of aryl iodides and bromides with methyl and ethyl acrylates was achieved at 140 °C. When styrene was employed as the substrate excellent conversion to trans-stilbene was observed using 5 mol% catalyst loading in the presence of TBAB. The catalysts are versatile and can couple various substrates in a non-toxic and benign solvent. After extraction of the organic product the catalyst containing aqueous layer could be recycled twice with a significant drop in the aryl halide conversion after the third recycle. No catalyst poisoning was observed in the mercury poisoning experiments with both catalysts and this proves that both catalytic systems function as molecular homogeneous catalysts.