Efficient Synthesis of Water-Soluble Alkyl-bis(m-sulfonated-phenyl)- and Dialkyl-(m-sulfonated-phenyl)-phosphines and Their Evaluation in Rhodium-Catalyzed Hydrogenation of Maleic Acid in Water

The combined application of P-31 NMR and pH measurements during the tri-isooctylamine-assisted aqueous/organic separation and purification steps after the sulfonation of diphenyl-alkyl-phosphines (Ph2PR; R = Me, n-Bu) and phenyl-dialkyl-phosphines (PhPR2; R = Me, n-Bu) resulted in the preparation of water-soluble alkyl-bis(m-sulfonated-phenyl)-(C6H4-m-SO3Na)(2)PR; R = Me, n-Bu) and dialkyl-(m-sulfonated-phenyl)- (C6H4-m-SO3Na)PR2; R = Me, n-Bu) phosphines in the presence of less than 0.5% phosphine oxides. When 2 equiv of the water-soluble phosphines were used per rhodium atom, no significant effect on the tu mover frequency of the hydrogenation of maleic acid can be observed by using these phosphines.