A new class of Rh(III) catalyst containing an aminoalcohol tethered to a tetramethylcyclopentadienyl group for asymmetric transfer hydrogenation of ketones

The Development of Phosphine‐Free "Tethered" Ruthenium(II) Catalysts for the Asymmetric Reduction of Ketones and Imines

“…In 2004–2005, Wills et al introduced a series of new catalysts, 5 – 8 , each containing the required tethering moiety (Figure ). The Rh(III)/Cp* complex 5 was derived from an amino alcohol,17 as was the Ru(II) complex 6 ,18 whereas 7 and 8 were prepared from DPEN 19–21. The aminoalcohol derivatives 5 and 6 proved to be effective as catalysts, but were not very stable, whereas the diamine‐derived catalysts worked more effectively.…”

An outstanding catalyst for asymmetric transfer hydrogenation in aqueous solution and formic acid/triethylamine

“…10 The performance of 8 was similar to that of the tethered Ru(II)TsDPEN catalyst 9 that we have previously reported 11 but represented a significant improvement over our earlier Rh(III) tethered catalyst 10 containing an amino alcohol ligand. 12 Upon examination of the publications in this area, we noted that, in contrast to the Ru(II)/TsDPEN 2 system, several successful catalysts based on Rh(III)/monotosylated diamines are derived from TsDAC 3. 8,9 We therefore sought to prepare the 'tethered' catalyst 11 from this diamine.…”

A Stereochemically Well-Defined Rhodium(III) Catalyst for Asymmetric Transfer Hydrogenation of Ketones

“…We have already reported the synthesis and use of the tethered amino alcohol/ Rh(III) catalyst 5; however, this proved to be unstable under the reduction conditions used. 10 In contrast, catalysts containing TsDPEN 2 have generally proved to be significantly more stable than those containing amino alcohols, and are therefore much more useful catalysts. Furthermore, and in contrast to Ru(II) and Rh(III) complexes of amino alcohol ligands, the TsDPEN 2 complexes are stable to the preferred formic acid/ triethylamine (FA/TEA) solvent system.…”