P-chiral Bisphosphane Ligands

This chapter describes atropisomeric biaryl bisphosphine ligands modified DIOP-type ligands P-chiral bisphosphane ligands other bisphosphane ligands and their applications in the enantioselective hydrogenation of olefins. 

Fig. 2.10 The ligand universe A stunning breadth of structural variation with members representing various motifs, e.g. atropisomeric biaryls, ferrocene-based bisphosphanes, P-chiral bisphosphanes, bisphosphites, monodentate phosphoramidites, AJ,P-ligands.

Although the first P-chiral bisphosphane (DIPAMP) was developed by Knowles over 30 years ago, the discovery of new efficient P-chiral bisphosphanes has been slow partly because of the difficulties in ligand synthesis. Pye and Rossen have developed a planar chiral bisphosphine ligand, [2.2]-PHANEPHOS 40, based on a paracyclophane backbone.37 The ligand has shown excellent enantioselectivity in Rh- and Ru-catalyzed hydrogenations. 

In 2011, Nadeau and coworkers [27] developed the first rhodium-catalyzed asymmetric arylation of N-benzyl nicotinate stJts (other C=N double bond substrates) with arylboronic acids. The use of an axial chiral bisphosphane ligand (i )-CTH-P-Phos gave a variety of six-substituted dihydropy-ridines with excellent enantioselectivities (Scheme 6.22). The usefulness of the method lies on the facile conversion of the dihydropyridines into the synthetically useful piperidines. 

Bis(phoshacyclopentadienyl)titanium(II) complexes, preparation and reactivity, 4, 265 Bisphosphanes on DIOP modification, 10, 7 in hydrogenations, 10, 7 in hydrogenations, P-chiral ligands, 10, 11 Bisphosphinidenes, with platinum(II), 8, 453 -54 Bisphosphinites, in hydrogenations, 10, 14 Bis(phosphinoalkyl-thioether)arenes, in ruthenium isocyanides, 7, 138... 

Many chiral ferrocene-based bisphosphane ligands with great structural variations have been developed recently. Togni and Spindler introduced non-Crsymmetric ferrocene-based Josiphos type ligands. Josiphos 38 has been found to be effective for Rh-catalyzed hydrogenation of a-acetamidocinnamate, dimethyl itaconate, and P-keto esters. A class of non-Cj-symmetrical ferrocene-based 1,5-diphosphane ligands (TaniaPhos 39) has also been... 

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