Selective reduction of dimethyl oxalate by ruthenium carbonyl carboxylates in homogeneous phase Part IV

Matteoli, Ugo; Menchi, Gloria; Bianchi, Mario; Piacenti, Franco

doi:10.1016/0304-5102(91)85135-o

Cited by 50 publications

(28 citation statements)

References 16 publications

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“…In a subsequent report, the authors compared the more bulky triisopropylphosphine-based catalyst in DMO hydrogenation [111]. This initially appeared worse than the first system, as it produced considerable decomposition products (65%).…”

Section: Hydrogenation Of Acids and Anhydridesmentioning

confidence: 99%

“…It is noteworthy that two of the most significant developments were made when the effect of different phosphine ligands were being investigated in more detail for the first time [111,114]. At present, it is difficult to predict the future for ester hydrogenation, but if the "catalysis community" invests time into the development of the process it could prove to be an environmentally benign method for carrying out reductions in the fine chemical and pharmaceutical industries.…”

Section: Hydrogenation Of Acids and Anhydridesmentioning

confidence: 99%

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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%

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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“…The first experiments were conducted using readily available and stable ruthenium starting materials such as RuCl 2 (PPh 3 ) 4 , which is known to be an excellent catalyst precursor for the transfer hydrogenation of ketones and aldehydes [12]. When RuCl 2 (PPh 3 ) 4 was applied as catalyst precursor for the hydrogenolysis of dimethyl oxalate, 37% conversion of ester 1 was observed using THF [10]. The catalyst precursor, however, showed poor selectivity and only a 12% yield of 2 was isolated after 16 h. No formation of 3 was observed; the remainders are unidentified side-products.…”

Section: Selection Of Ruthenium Precursormentioning

confidence: 99%

“…Another example of a catalyst applicable for the hydrogenolysis of esters is the complex developed by Grey et al [9]. The scope of both systems is limited, they are only applicable in the hydrogenolysis of activated esters, such as dimethyl oxalate [10] or fluorinated esters [9].…”

Section: Introductionmentioning

confidence: 99%

“…In this paper we describe the selection of suitable ruthenium complexes and ligands as catalyst precursors for the hydrogenolysis of esters to alcohols. Catalyst precursors were evaluated based on their activity and selectivity in the hydrogenolysis of dimethyl oxalate (1), which, due to its structural properties, is activated for hydrogenolysis, and can act as an excellent probe (Scheme 2) [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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