Homogeneous asymmetric transfer hydrogenation of ketones using a ruthenium catalyst anchored on chitosan: natural chirality at work

Abstract

A pivaloyl functionalized chitosan biopolymer was used as a polyligand for the [Ru(p-cymene)Cl2] moiety. The functionalized biopolymer containing a metal to saccharide ratio of 0.33 was used as a catalyst for the asymmetric transfer hydrogenation of ketones. The reactions gave yields up to 80% 65 65

Catalytic sugar-assisted transfer hydrogenation with Ru(II), Rh(III) and Ir(III) halfsandwich complexes

“…In 2012, Fontaine et al published a modified chitosan with a protecting group at the hydroxyl-function of C6 and its application as a polyligand in the synthesis of Á 6 -p-cymene ruthenium(II) complexes. Transfer hydrogenation of acetophenone with 2-propanol and sodium 2-propanolate catalyzed by the obtained polycomplex led to (S)-1-phenylethanol with an enantiomeric excess up to 72% [14].…”

“…The formerly unknown precursor complexes with methyl 2,3-diamino-4,6-O-benzylidene-2,3-dideoxy-␣-D-hexopyranosides (compounds 1-4, Chart 1), methyl 2-amino-4,6-OChart 1. Diaminomonosaccharides 1-4, methyl 2-amino-4,6-O-benzylidene-2,3-dideoxy-3-tosylamido-␣-D-glucopyranoside (5) and corresponding diamino derivatives (S)-2,2 -diamino-1,1 -binaphthalene (6) and (R,R)-1,2-diphenylethylenediamine (7) and their halfsandwich complexes of iridium(III), -rhodium(III) and ruthenium(II) (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) for transfer hydrogenation ([T-4-R] and [T-4-S] denote the absolute configuration of the metal center in a pseudo-tetrahedral environment following the CIP rules).…”

Chitosan as a Natural Polymer for Heterogeneous Catalysts Support: A Short Review on Its Applications

“…The as-prepared catalyst had high yields and excellent selectivities on the hydration of nitriles and could be recovered and reused without affecting the reactivity. Babin et al [48] also reported the use of a pivaloyl functionalized chitosan catalyst [Ru(ρ-cymene)Cl2] for the asymmetric transfer hydrogenation of ketones with up to 80% of reaction yield.…”

Imidazolium ion tethered TsDPENs as efficient water-soluble ligands for rhodium catalyzed asymmetric transfer hydrogenation of aromatic ketones

“…In 2001 the first example of Ru(II)-catalyzed ATH of ketones with HCO 2 Na as a hydride source in aqueous media was reported [17]. Since this discovery, a number of water-soluble ligands and catalysts have been developed for ATH in aqueous media providing the reduction products in high conversion yields and enantioselectivities [18][19][20][21][22][23][24][25][26]. However, a major problem associated with these catalytic systems is that the low substrate/catalyst (S/C) ratio (normally S/C = 100) and large excess amounts of hydride donor (≥ 5 equiv.…”