Rhodium-catalyzed hydroformylation diphosphine ligands

Escudero-Adan, E.C., Freixa, Z. and van Leeuwen. P.W.N.M. (2007) Catalysis by design Wide-bite-angle diphosphines by assembly of ditopic ligands for selective rhodium-catalyzed hydroformylation. Angeiv. Chem., Int. Ed., 46. 7247—4750. 

Kamer. P.C.J.. van Leeuwen, P.W.N.M., Goubitz, K. and Fraanje, J. (1995) New diphosphine ligands based on heterocychc aromatics inducing very high regioselectivity in rhodium-catalyzed hydroformylation - Effect of the bite angle. Organometallics, 14, 3081-3089. 

The series of new diphosphines have been tested in the rhodium-catalyzed hydroformylation (Table 1) of 1-octene. The reaction rates for the catalysts derived from the pyridyl-modified ligands 10-12 and POPpy are higher than those of BISBI and 13, which is consistent with earlier observations made for the pyridyl-modified triphenylphosphines [19]. 

Hughes, O.R. and Unruh, J.D. (1981) Hydroformylation catalyzed by rhodium complexes with diphosphine ligands. Journal of Molecular Catalysis, 12,71 Sanger, A.R. (1977) Hydroformylation of 1-hexene catalysed by complexes of rhodium(I) with di- or tritertiary phosphines. Journal of Molecular Catalysis, 3,221 Sanger, A.R. and Schallig, L.R. (1977) The structures and hydroformylation catalytic activities of polyphosphine complexes of rhodium(l), and related complexes immobilised on polymer supports. Journal of Molecular Catalysis, 3, 101 Pittman, C.U. and Hirao, A. (1978) Hydroformylation catalyzed by cis-chelated rhodium complexes - extension to polymer-anchored cis-chelated rhodium catalysts. The Journal of Organic Chemistry, 43, 640. 

The ligands 29-38 have been applied in a variety of catalytic reactions, but their initial purpose was to serve in rhodium-catalyzed hydroformylation. The selectivity of the xantphos ligands in the rhodium-catalyzed hydroformy-lation was tested with the use of 1-octene (Table 2). DPEphos, having a calculated natural bite angle of 102°, induced an enhanced, though moderate selectivity (compared to most diphosphines), but no isomerization was detected. The... 

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