Suitable ligands for homogeneous ruthenium-catalyzed hydrogenolysis of esters

Engelen, M.C. van; Teunissen, Herman T.; Vries, Johannes G. de; Elsevier, Cornelis J.

doi:10.1016/s1381-1169(03)00427-8

Cited by 101 publications

(41 citation statements)

References 30 publications

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“…There has been one further, recent development in this area. Elsevier and coworkers studied DMO hydrogenation using a broader range of catalysts, and under milder conditions than those used by Matteoli et al [112,113]. Elsevier and colleagues showed that tetra-and tri-dentate phosphines, when used in combination with [Ru(acac) 3 ], are very promising pre-catalysts for this class of reaction (Table 15.17).…”

Section: Hydrogenation Of Acids and Anhydridesmentioning

confidence: 99%

Homogeneous Hydrogenation of Aldehydes, Ketones, Imines and Carboxylic Acid Derivatives: Chemoselectivity and Catalytic Activity

Clarke¹,

Roff²

2006

The Handbook of Homogeneous Hydrogenation

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414Scheme 15.1 Hydrogenation of n-butyraldehyde. Table 15.1 Hydrogenation of aldehydes with [IrH 3 (PPh 3 ) 3 ] in acetic acid. Substrate Catalyst [mol.%] Temperature [8C] Yield [%] TON TOF [h -1 ] 0.022 80 73 3280 492 0.023 110 82 3540 177 0.032 90 64 2000 89 0.039 110 80 2030 81 0.013 110 98 7780 259 examined for a,b-unsaturated aldehydes (Scheme 15.2). Using the [IrH 3 (PPh 3 ) 3 ] complex in acetic acid for the hydrogenation of crotonaldehyde resulted in the formation of the saturated alcohol (Scheme 15.3). It was also noted that this catalyst did not allow for ketone hydrogenation at 10 bar. Other attempts to use iridium PPh 3 complexes such as [IrCl(PPh 3 ) 3 ], [IrCl(CO)(PPh 3 ) 2 ], [Ir(ClO 4 )(CO)(PPh 3 ) 2 ] and [Ir(CO)(PPh 3 ) 3 ]ClO 4 to hydrogenate unsaturated aldehydes did not yield great results [3], mainly because these catalysts suffered from low activity and selectivity.The catalytic system of [Ir(COD)Cl] 2 with an excess of the bulky phosphine P(o-MeOPh) 3 under transfer hydrogenation conditions of propan-2-ol and KOH was used successfully in the selective hydrogenation of cinnamaldehyde (Scheme 15.4) [4]. Selectivity and activity were found to increase with increasing P/Ir ratios, and complete conversion was achieved in as little as 5 minutes (turnover frequency (TOF) *6000 h -1 ). Hydrogenation of Aldehydes 415Scheme 15.2 Distribution of products in the hydrogenation of a,b-unsaturated aldehydes. Scheme 15.3 Hydrogenation of crotonaldehyde with [IrH 3 (PPh 3 ) 3 ] in acetic acid. Scheme 15.4 Transfer hydrogenation of cinnamaldehyde.Using molecular hydrogen as the reducing agent, [Ir(COD)(OCH 3 )] 2 with an excess of tertiary phosphine was better than [Ir(COD)Cl] 2 for the selective hydrogenation of cinnamaldehyde [5]. In these studies, a great dependence on solvent and ligand was reported. A variety of different phosphines, which were markedly different in their steric and electronic properties, were examined in this reaction. In propan-2-ol the most effective phosphine was PCy 2 Ph which gave 94% yield (TOF 235 h -1 ) of the unsaturated alcohol in a 2 h reaction under 30 bar H 2 at 100 8C. Phosphines such as PCyPh 2 , PPhPr i 2 , PPh 2 Pr i and PEtPh 2 were also effective in giving over 95% selectivity. The less-effective phosphines were PEt 2 Ph, PMePh 2 , PBu i 3 and PMe 2 Ph. Reactions that were performed in toluene were generally less effective.More recent advances in iridium-catalyzed aldehyde hydrogenation have been through the use of bidentate ligands [6]. In the hydrogenation of citral and cinnamaldehyde, replacing two triphenylphosphines in [IrH(CO)(PPh 3 ) 3 ] with bidentate phosphines BDNA, BDPX, BPPB, BISBI and PCP ( Fig. 15.1) led to an increase in catalytic activity. a) Selectivity of allylic alcohol formed as a percentage of total hydrogenation products. b) TOF (h -1 ) expressed for conversion of starting material. Hydrogenation of Aldehydes 419Scheme 15.5 Preparation of cationic DiPFc catalyst.

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Section: Hydrogenation Of Acids and Anhydridesmentioning

confidence: 99%

Homogeneous Hydrogenation of Aldehydes, Ketones, Imines and Carboxylic Acid Derivatives: Chemoselectivity and Catalytic Activity

Clarke¹,

Roff²

2006

The Handbook of Homogeneous Hydrogenation

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“…This also raises questions about the mode of operation of the different additives, zinc having been suggested to act by enhancing the reduction of the Ru(III) precursor to Ru(II) [12]. This mode of operation would be expected to yield the reduced induction period which is observed, but does not explain the enhancement or retardation of rate depending upon substrate.…”

Section: Catalysismentioning

confidence: 99%

“…Ph ligand (Figure 1, 1) in combination with ruthenium allows hydrogenation of DMO to ethane--1,2--diol (ED) at 80 bar H 2 and 100 o C [12,13,20]. A notable example not based upon phosphines is the TriSulf Bu ligand (Figure 1, 2), which combines facial capping coordination with electron--releasing character, and allows selective hydrogenation of DMO to methyl glycolate (MG),…”

Section: Triphosmentioning

confidence: 99%

“…Two variants of the N--TriPhos ligand were selected for investigation; the known N--TriPhos Ph ligand (Figure 2, 6) and the new N--TriPhos Et ligand (Figure 2, 7) featuring diethylphosphanyl moieties, which it was envisaged would enhance the electron density at the ruthenium metal centre. This should accelerate oxidative addition processes, and enhance the hydridic nature of the ruthenium--hydride moiety increasing reactivity towards the carbonyl functionality of the ester group [12]. Herein, we wish to report the use of N--TriPhos ligands for the ruthenium--catalysed hydrogenation of dimethyl oxalate and draw comparisons with the TriPhos--based system.…”

mentioning

confidence: 99%

“…The majority of examples have featured phosphine ligands, with electron rich trialkylphosphines showing promise, whilst facially capping tripodal phosphine scaffolds are the most effective [12,13]. However, these systems are limited to activated esters, dimethyl oxalate (DMO) being the commonly studied substrate (Scheme 1).…”

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