Synthesis and use of water-soluble sulfonated dibenzofuran-based phosphine ligands

The syntheses of three triphenylphosphine analogues with one, two or three phenyl groups replaced by 2-dibenzofuranyl groups, respectively, and one enantiopure analogue of the atropisomeric diphosphine MeO-BIPHEP with all four phenyl groups replaced by 2-dibenzofuranyl are reported. Sulfonation of these compounds with sulfuric acid at rt proceeded with complete regioselectivity at the 8-position in the dibenzofuran moieties. These results proved the usefulness of dibenzofuran as a structural moiety in the synthesis of water-soluble phosphine ligands. The dibenzofuran-based, water-soluble triphenylphosphine analogues were used as ligands in palladium-catalysed aqueous phase Heck and Suzuki reactions and in the rhodium-catalysed two-phase hydroformylation of propene. (C) 1999 Elsevier Science Ltd. All rights reserved.