Transfer hydrogenation reduction of ketone catalyzed by Ru(II) and Rh(I) complexes with ligands derived from (1R,2R)-cyclohexane-1,2-diamine

Abstract

A number of bidenate and tridentate ligands were synthesized from chiral mono sulfonamides, which were derived from cyclohexane-1,2-diamine. These ligands were tested with Ru(II) and Rh(I) for catalytic activity in the transfer hydrogenation reaction of ketone.

Heterocycle-containing Noyori–Ikariya catalysts for asymmetric transfer hydrogenation of ketones

“…4-chromanone and tetralone, were also reduced in very high ee; these compounds are known to be very compatible with ATH using Noyori–Ikariya catalysts. 2,5–10,16 In addition, substrates containing substituents at the α-position to the ketone, including chloro and phenoxy, were also compatible substrates. The ATH of the pentafluorophenyl analogue of acetophenone is known to be difficult to achieve in high ee due to the electron-poor nature of the aromatic ring, 4 d but could be reduced in up to ca .…”

“…7 Substitution of the non-tosylated amine is also tolerated. 8 The ligand can also be modified at the sulfonamide with functional groups that can, for example, improve the solubility of the catalysts in water. 9 Although there are many other reported modifications to the sulfonamide component, 10 we were aware of very few examples of the replacement of the tosyl group with a heterocyclic sulfonamide, a modification which could potentially alter the reactivity and selectivity of the catalysts.…”

“…13 Apart from moderating the selectivity and activity of the catalysts, heterocyclic groups may also help to facilitate the recovery of the catalysts after use, and improve their solubility in specific solvents, including water, as has been the case with other modifications. 5–10…”