Ligands TANIAPHOS

The recent introduction of the TaniaPhos ligands (34) provides another excellent catalyst system for the reduction of dehydroamino acid derivatives and enol... 

Spindler F, Malan C, Lotz M, Kesselgruber M, Pittelkow U, Rivas-Nass A, Briel O, Blaser HU (2004) Modular chiral ligands the profiling of the Mandyphos and Taniaphos ligand families. Tetrahedron Asym 15 2299-2306... 

The catalytic behaviour of MandyPhos (1) and TaniaPhos (2) ligands (see structures in Scheme 23.1) in chiral hydrogenations was explored in former publications by applying in situ catalytic procedures (1). 

Pre-Catalyst Systems Using TaniaPhos/MandyPhos Ligands... 

The coordination chemistry of MandyPhos and TaniaPhos with rhodium and palladinm has been explained by Knochel (1, Knochel). The chemistry of ligands snch as Duphos or BINAP with all relevant established ratheninm(II) precnrsors is known and was derived from their bidentating coordination behaviour ... 

Precursors synthesis The observed reaction of TaniaPhos (2) with [Ru(benzene)Cl2]2 or [Ru(p-cymene)Cl2]2 confirmed that defined and stable metal-complexes could also be synthesized with this ligand. 

It was not possible to isolate defined complexes with clear bidentate coordination for the ligands MandyPhos and TaniaPhos using established ruthenium precursors such as [Ru(COD)Cl2]x, [Ru(benzene)Cl2]2, [Ru(p-cymene)Cl2]2,... 

Riant et al. applied the catalytic system [CuF(Ph3P)3]2MeOH (0.1-1 mol%) and PhSiH3 (140 mol %) in the combination with Ph-TANIAPHOS as ligand to the syn-selective reductive coupling of aldehydes and methyl... 

A series of non-f, -symmetrical ferrocene-based 1,5-diphosphane ligands (TaniaPhos) has been developed by Knochel.88,88a,88b The ligands have been effectively used in Rh- or Ru-catalyzed asymmetric hydrogenations. The ligand 39, which has an MeO group at the chiral carbon center, has shown excellent applications in the hydrogenation of several olefin and ketone substrates.89 Weissensteiner and Spindler have reported a series of structurally different... 

A broad screening of ligands and ionic liquids was carried out by Feng et al. [104]. For rhodium-catalyzed hydrogenation of enamides the best catalysts were found to be the rhodium-ferrocenyl-diphosphine complexes with taniaphos, josiphos, walphos and mandyphos as ligands (Fig. 41.9). 

The second approach starts from achiral allylic substrates and uses a chiral metal catalyst. Among all ligands which have been tested binaphtol-derived phosphoramidites like 174 have led to excellent regio- and enantioselectivities (equation 103) °. Highly stereoselective substitutions are also obtained using ligand 175 (Taniaphos, equation 104... 

Figure 3.3 TANIAPHOS and JOSIPFIOS-type ligands used in the asymmetric reduction of en amides...

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... 

Sammakia and Uemara, the development of the 1,5-bisphosphine Taniaphos by Knochel and coworkers, and more recently by Fu for the preparation of chiral heterocycles, ferrocene-based ligands in asymmetric catalysisJ For a specialized recent review concerning apphcations of chiral ferrocene ligands in asymmetric catalysis, the reader may consult a review by Carretero et alP ... 

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