Further ‘tethered’ Ru(II) catalysts for asymmetric transfer hydrogenation (ATH) of ketones; the use of a benzylic linker and a cyclohexyldiamine ligand

Versatile Iridicycle Catalysts for Highly Efficient and Chemoselective Transfer Hydrogenation of Carbonyl Compounds in Water

“…α‐Halo‐, hydroxy‐ and nitrile‐substituted ketones are more challenging to reduce due to the ease of dissociation/decomposition of these α‐functional groups under acidic and/or basic conditions 6b–i. l, 8, 16 However, the current reduction system overcomes these challenges. After modification of the reaction conditions, the desired products were obtained with excellent yields for almost all of these problematic ketones.…”

“…k–p Of further interest are β‐hydroxyhalo compounds, which have found use in the preparation of numerous compounds for pharmaceuticals, fine chemicals and functional materials 6b. e, i, l–m…”

“…8 However, few catalysts are known that are capable of selective TH of a wide range of α‐substituted ketones 6a–i. l–m, 9 In addition, most of the reactions are conducted in organic solvents, which generates unwanted waste. One way of minimising the environmental impact caused by the use of organic solvents would be the use of water as the reaction medium.…”

“…However, the reduction of α‐substituted ketones with TH in water is challenging, because the substrates/products are usually acid and/or base sensitive 6c–e. l, 9a, c Thus, there is a need for a catalyst that is versatile, active and chemoselective for the TH of α‐substituted ketones with diverse properties to form the corresponding secondary alcohols.…”

Application of Proline‐Functionalised 1,2‐Diphenylethane‐1,2‐diamine (DPEN) in Asymmetric Transfer Hydrogenation of Ketones

“…The organic layer was filtered through a plug of silica and the solvent removed under reduced pressure to leave the product which was purified by column chromatography if necessary. Characterisation data and ee determination methods for reduction products [43][44][45][46][47][48][49][50] are given in the Supporting Information.…”