Synthesis of pyrrolyl-, indolyl-, and carbazolylphosphanes and their catalytic application as ligands in the hydroformylation of 2-pentene

The synthesis of pi -acceptor ligands of the type PArxR3-x (x = 0-2; R = py rrolyl, indolyl, carbazolyl; Ar = aryl) (1-8, 10, 12, 13) and P(pyrrolyl)(2 )(carbazolyl) (11) is described. These ligands can be prepared in good to e xcellent yields by treatment of the corresponding free,e heterocyclic amine s with phosphorus chlorides in the presence of base. The utilization of pyr rolyl-, indolyl-, and carbazolylphosphanes in the rhodium-catalyzed hydrofo rmylation of 2-pentene demonstrates the influence of the ligand pi -acidity on regioselectivity and activity in the hydroformylation of internal olefi ns. In general, increasing pi -acidity of the ligand results in an increase d yield of the linear oxo product, The best n/iso ratios of about 60:40 are obtained at low synthesis gas pressure (10 bar) in the presence of the P(p yrrolyl)(3) (1) ligand.