Synthesis of polyethylene glycol supported chiral monosulfonamide and its application in asymmetric transfer hydrogenation of prochiral ketones

Abstract

A new polyethylene glycol supported chiral monosulfonamide was conveniently synthesized from (R,R)-1,2-diphenylethylenediamine. The ruthenium catalyst prepared from polyethylene glycol supported chiral monosulfonamide with [RuCl 2 (p-cymene)] 2 was used in the asymmetric transfer hydrogenation of prochiral ketones in neat water with good to excellent conversions and enantioselectivities. The catalyst could be easily recovered and reused several times.

The Golden Age of Transfer Hydrogenation

“…TH in water was relatively unstudied until a few years ago. 128,212,428 Various approaches using ruthenium catalysts containing water-soluble ligands, however, have been investigated; in particular, polyethylene-glycol-anchored 429,430 and aryl-sulfonated 91,221,431 TsDPEN-type ligands were synthesized. Subsequently some water-soluble polymer-supported, 252 439 Considerable enhancement of activity was observed upon using a cationic surfactant such as CTAB (cetyltrimethylammonium bromide) or CPB (cetylpyridine bromide), presumably caused by accelerated transformation of formate ions from aqueous solution to micellar phases (Scheme 40).…”

“…Moreover, the use of water can sometimes lead to remarkable rate acceleration in catalysis as compared to organic solvents, this phenomenon being called the “water effect”. TH in water was relatively unstudied until a few years ago. ,, Various approaches using ruthenium catalysts containing water-soluble ligands, however, have been investigated; in particular, polyethylene-glycol-anchored , and aryl-sulfonated ,, TsDPEN-type ligands were synthesized. Subsequently some water-soluble polymer-supported, ,, chitosan-anchored or surface-active , ruthenium catalysts have been used in TH reactions.…”

“…TH in water was relatively unstudied until a few years ago. 128,212,428 Various approaches using ruthenium catalysts containing water-soluble ligands, however, have been investigated; in particular, polyethylene-glycol-anchored 429,430 and aryl-sulfonated 91,221,431 TsDPEN-type ligands were synthesized. Subsequently some water-soluble polymer-supported, 252,432,433 chitosan-anchored 434 or surface-active 435,436 ruthenium catalysts have been used in TH reactions.…”

Opportunities Offered by Chiral η6-Arene/N-Arylsulfonyl-diamine-RuII Catalysts in the Asymmetric Transfer Hydrogenation of Ketones and Imines

“…Another polyethylene glycol-supported ligand ( 16 ) was synthesized in 2010 [ 113 ]. In the ATH of acetophenone using [Ru(η 6 - p -cymene)Cl 2 ] 2 and HCOONa, 97% ee was observed (entry 15).…”

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

“…The soluble polymer 126 containing a TsDPEN (9) unit was used in combination with BRu for the ATH of aromatic and heterocyclic ketones with formic acid and triethylamine as the reaction mixture, so variable conversions but excellent enantioselectivities were achieved. 103 The three polymer-supported diamine derivatives 127, 104 128 105 and 129 106 were effective with CRu in the ATH of aromatic, heterocyclic and ferrocenyl ketones using in all cases sodium formate under aqueous conditions. Results were generally very good in terms of yields and enantioselectivities.…”