Alternative Energy Input for Transfer Hydrogenation using Iridium NHC Based Catalysts in Glycerol as Hydrogen Donor and Solvent

Azua, Arturo; Mata, José A.; Peris, Eduardo; Lamaty, Frédéric; Martinez, Jean; Colacino, Evelina

doi:10.1021/om300109e

Cited by 87 publications

(68 citation statements)

References 56 publications

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“…The zero-order rate of formation of the (S)-enantiomer changes proportionally with catalyst concentration (Fig.4) The catalytic rate constants for the transfer hydrogenation of imines (11) or (12) to chiral amines (13) or (14), respectively, catalysed by the iridium complex 3 in acetonitrile and dichloromethane are given in Table 1. The dimethoxy imine (12) is at least 10-fold more basic than the unsubstituted imine (11) 32 and yet there is less than a twofold difference in reactivity for the formation of both enantiomers ( Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…2,3,4 The first homogeneous catalytic systems appeared in the late 1960s and were based on iridium compounds 5,6 which were followed by the introduction of the versatile pentamethylcyclopentadienyl anion iridium and rhodium (Cp*Ir and Cp*Rh) catalyst precursors for these transformations 7,8,9,10 and their variants. 11,12,13 Although the highly selective asymmetric reduction of alkenes and ketones has been accomplished using chiral rhodium and ruthenium catalysts, 14 the hydrogenation of imines using similar catalysts has proved much less successful. 15 Furthermore, most enantioselectivities obtained are moderate and require a high catalyst loading.…”

Section: Introductionmentioning

confidence: 99%

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The kinetics and mechanism of the organo-iridium-catalysed enantioselective reduction of imines

et al. 2016

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The iridium complex of pentamethylcyclopentadiene and (S,S)-1,2-diphenyl-N ′ -tosylethane-1,2-diamine is an effective catalyst for the asymmetric transfer hydrogenation of imine substrates under acidic conditions. Using the Ir catalyst and a 5:2 ratio of formic acid: triethylamine as the hydride source for the asymmetric transfer hydrogenation of 1-methyl-3,4-dihydroisoquinoline and its 6,7-dimethoxy substituted derivative, in either acetonitrile or dichloromethane, shows unusual enantiomeric excess (ee) profiles for the product amines. The reactions initially give predominantly the (R) enantiomer of the chiral amine products with >90% ee but which then decreases significantly during the reaction. The decrease in ee is not due to racemisation of the product amine, but because the rate of formation of the (R)-enantiomer follows first-order kinetics whereas that for the (S)-enantiomer is zero-order. This difference in reaction order explains the change in selectivity as the reaction proceeds -the rate formation of the (R)-enantiomer decreases exponentially with time while that for the (S)-enantiomer remains constant. A reaction scheme is proposed which requires rate-limiting hydride transfer from the iridium hydride to the iminium ion for the first-order rate of formation of the (R)-enantiomer amine and rate-limiting dissociation of the product for the zero-order rate of formation of the (S)-enantiomer.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The kinetics and mechanism of the organo-iridium-catalysed enantioselective reduction of imines

et al. 2016

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“…In the case of MW heating, nucleation takes place along any plane, whereas in the reflux method, it occurs in all planes and axes resulting in a uniform spherical shape. 10 as catalysts in the reduction of aldehydes and ketones in glycerol. Their catalytic properties were compared with those of previously reported iridium complexes used in the transfer hydrogenation reaction, where glycerol is both solvent and hydrogen donor, under MW, US and oil bath conditions (Scheme 7).…”

Section: Ch2oh-ch(oh)-ch2oh → Ch2oh-ch(oh)-cho + H2 Ch2oh-ch(oh)-ch2omentioning

confidence: 99%

Glycerol: a solvent and a building block of choice for microwave and ultrasound irradiation procedures

Cintas¹,

Tagliapietra

Gaudino

et al. 2014

Green Chem.

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Glycerol has the potential to be both an excellent renewable solvent in modern chemical processes and a versatile building block in biorefineries. Both of these potential applications may be made easier and more convenient by microwave and/or ultrasound ir radiation. As glycerol is a nontoxic, biodegradable compound, it will provide important environmental benefits to new platform products. Furthermore, significant markets in polymers, polyethers, fuel additives, nanoparticles and other valuable compounds may well be opened up by cutting down the high purification cost of glycerol. The aim of this review is to highlight the best literature examples of glycerol being used, either as solvent or as a reagent, to give interesting results under microwave or ultrasound irradiation.

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“…An analogous mechanistic pathway to that proposed by Crabtree et al for lactic acid formation has been postulated. Remarkably, industrial glycerol (86-88% purity) was converted using complex reduction of ketones [57,58]. In previous reports from Crabtree and coworkers, bis(carbene)iridium complexes proved highly active in hydrogen transfer of carbonyl compounds [59][60][61].…”

Section: From Glycerol To Lactic Acidmentioning

confidence: 99%

Lactic acid and hydrogen from glycerol via acceptorless dehydrogenation using homogeneous catalysts

Bottari¹,

Barta²

2015

Recyclable Catalysis

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Acceptorless dehydrogenation of alcohols has emerged as a powerful methodology for the valorization of biomass derived platform chemicals and building blocks. In this review we provide a short overview of the advantages and possible product outcomes of this method. The main focus will be devoted to the conversion of glycerol, which is the major waste product of biodiesel production, to lactic acid. While extensive research addresses the development of heterogeneous catalysts, recently new and highly active iridium and ruthenium complexes have also been reported. These novel homogeneous catalysts are even more active than the already reported heterogeneous systems and enable the direct conversion of glycerol into lactic acid and molecular hydrogen. While the product hydrogen might be used either as fuel or as reducing agent for other processes, lactic acid is a platform chemical widely employed by the polymer, pharmaceutical and food industries. The used catalytic methodology is atom-economic, waste-free and is uniquely suited for the efficient conversion of renewable resources.

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Alternative Energy Input for Transfer Hydrogenation using Iridium NHC Based Catalysts in Glycerol as Hydrogen Donor and Solvent

Cited by 87 publications

References 56 publications

The kinetics and mechanism of the organo-iridium-catalysed enantioselective reduction of imines

The kinetics and mechanism of the organo-iridium-catalysed enantioselective reduction of imines

Glycerol: a solvent and a building block of choice for microwave and ultrasound irradiation procedures

Lactic acid and hydrogen from glycerol via acceptorless dehydrogenation using homogeneous catalysts

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