Phosphanorbornadienephosphonates as a New Type of Water-Soluble Phosphines for Biphasic Catalysis

The reaction of (phenylethynyl)phosphonates or- phosphonamides with 1-phenyl-3,4-dimethylphosphole at 140 °C affords the corresponding α-P(O)-substituted 1-phosphanorbornadienes ( 1 − 3 ). The corresponding PO 3 Na 2 salt ( 5 ) displays some solubility in water (20 g/L) but is a poor ligand both for the rhodium-catalyzed hydrogenation and hydroformylation of olefinic bonds. The reaction of an unsubstituted ethynylphosphonamide with the same phosphole yields a 3:1 mixture of α- and β-P(O)-substituted 1-phosphanorbornadienes 7 and 8 . The β-PO 3 Na 2 salt ( 10 ) is a good ligand for the hydrogenation of ( Z )-α-( N -acetamido)cinnamic acid and displays a high solubility in water (230 g/L). The chelation of rhodium by the α-P(O)-substituted 1-phosphanorbornadienes probably explains the loss of hydrogenation efficiency for [RhL 2 ] + when L = 5 .