The importance of 1,2-anti-disubstitution in monotosylated diamine ligands for ruthenium(II)-catalysed asymmetric transfer hydrogenation

Hayes, Aidan; Clarkson, Guy J.; Wills, Martin

doi:10.1016/j.tetasy.2004.05.025

Cited by 34 publications

(18 citation statements)

References 47 publications

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“…In aqueous solvents, the most promising systems are based on water-soluble or polymer-supported amino-sulfonamide scaffolds derived from Noyori's system (35)(36)(37)(38)(39)(40). In the same spirit, we synthesized a series of achiral aminosulfonamide ligands Biot-q-LH (Scheme 2) and set out to test their potential in combination with two [ 6 -(arene)Ru] 2ϩ moieties by using (strept)avidin as host proteins.…”

Section: Resultsmentioning

confidence: 99%

Artificial metalloenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation

Letondor

Humbert

Ward

2005

Proc. Natl. Acad. Sci. U.S.A.

184

123

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Most physiological and biotechnological processes rely on molecular recognition between chiral (handed) molecules. Manmade homogeneous catalysts and enzymes offer complementary means for producing enantiopure (single-handed) compounds. As the subtle details that govern chiral discrimination are difficult to predict, improving the performance of such catalysts often relies on trial-and-error procedures. Homogeneous catalysts are optimized by chemical modification of the chiral environment around the metal center. Enzymes can be improved by modification of gene encoding the protein. Incorporation of a biotinylated organometallic catalyst into a host protein (avidin or streptavidin) affords versatile artificial metalloenzymes for the reduction of ketones by transfer hydrogenation. The boric acid⅐formate mixture was identified as a hydrogen source compatible with these artificial metalloenzymes. A combined chemo-genetic procedure allows us to optimize the activity and selectivity of these hybrid catalysts: up to 94% (R) enantiomeric excess for the reduction of p-methylacetophenone. These artificial metalloenzymes display features reminiscent of both homogeneous catalysts and enzymes.second coordination sphere ͉ asymmetric catalysis ͉ chemzymes T he asymmetric reduction of CAO and CAN bonds is one of the most fundamental transformations in organic chemistry (1-3). Although enzymatic and organometallic catalysis have evolved along very different paths, both methodologies can achieve high levels of enantioselection for this transformation.Oxidoreductases such as alcohol dehydrogenases can perform this task very efficiently and selectively (4-7). To achieve this, however, these enzymes rely on precious cofactors NAD(P)H, which need to be regenerated (8). Alternatively, whole cells can be used. These contain multiple dehydrogenases, all of the necessary cofactors, and the metabolic pathways for their regeneration (5).Asymmetric transfer hydrogenation (Meerwein-PonndorfVerley reduction) based on d 6 piano-stool complexes has proven to be versatile for the asymmetric reduction of ketones and imines (2, 9, 10). Regeneration of the organometallic hydride is achieved by a ␤-H abstraction between the catalyst precursor and a sacrificial hydrogen donor (isopropanol or formate). These catalysts nicely complement other organometallic systems that rely on dihydrogen (3).It is interesting to note that theoretical studies suggest that the transfer hydrogenation catalyzed by d 6 piano-stool complexes proceeds without coordination of the substrate to the metal, as illustrated in transition-state structure 1 (11-14) (Fig. 1). The chiral recognition pattern for this organometallic transformation is thus reminiscent of enzymatic catalysis. Indeed, the second coordination sphere provided by a protein is optimized to steer the enantiodiscrimination step without necessarily requiring covalent (or dative) binding of the substrate to the enzyme.In recent years, chemo-enzymatic catalysis has attracted increasing attention. In such systems, an ...

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Section: Resultsmentioning

confidence: 99%

Artificial metalloenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation

Letondor

Humbert

Ward

2005

Proc. Natl. Acad. Sci. U.S.A.

184

123

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“…It was observed that the presence of the η 6 -arene moiety is essential for the success of the behavior of the catalysts, due to its stabilizing ability of the transition state by π-interactions (Figure 2/benzene (1)/ C(sp 2 )H/π, alkylated arenes (2)/ C(sp 3 )H/π). With the investigation of a series of monotosylated diamines with different configurations in the hydrogen transfer reaction of acetophenone, a better understanding of the enantiocontrol of Noyori's complex was provided [54]. Ruthenacycles (with tethered structural motif and with chiral diphosphine or chiral pyridine as ligands) showed high activity and enantioselectivity in the reduction of aryl alkyl ketones ( The success of the Ru-arene system with the variety of different ligands can be seen clearly in the huge amount of results that have been reported [1,21,28].…”

Section: Hydrogen Transfer With Rutheniummentioning

confidence: 99%

“…Ruthenacycles (with tethered structural motif and with chiral diphosphine or chiral pyridine as ligands) showed high activity and enantioselectivity in the reduction of aryl alkyl ketones ( The success of the Ru-arene system with the variety of different ligands can be seen clearly in the huge amount of results that have been reported [1,21,28]. Several results towards the reduction of acetophenones (Scheme 11) and acylbenzenes (Scheme 12) obtained with RuCl2PPh3(oxazferrphos) [58][59][60], RuCl(1,4-cymene)(prolinamide) [58][59][60], RuCl(hexamethylbenzene)(azanorbornylmethanol) [61], and with RuCl(1,4-cymene)(azanorbornylmethanol) [59,60,62], is depicted in Figure 11 The Ru-arene system (Scheme 10, complex 26) (and Rh-or Ir-cyclopentadienyl complexes), such as Noyori's catalyst, contains 1,2-amino alcohols or monotosylated diamine ligands (in some cases phosphine-oxazoline derivatives) in their structure, a combination that leads to a catalyst system with the broadest substrate scope ( Figure 2) [28,54]. It was observed that the presence of the η 6 -arene moiety is essential for the success of the behavior of the catalysts, due to its stabilizing ability of the transition state by π-interactions (Figure 2/benzene (1)/ C(sp 2 )H/π, alkylated arenes (2)/ C(sp 3 )H/π).…”

Section: Hydrogen Transfer With Rutheniummentioning

confidence: 99%

Hydrogen Transfer Reactions of Carbonyls, Alkynes, and Alkenes with Noble Metals in the Presence of Alcohols/Ethers and Amines as Hydrogen Donors

Baráth

2018

Catalysts

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Hydrogen transfer reactions have exceptional importance, due to their applicability in numerous synthetic pathways, with academic as well as industrial relevance. The most important transformations are, e.g., reduction, ring-closing, stereoselective reactions, and the synthesis of heterocycles. The present review provides insights into the hydrogen transfer reactions in the condensed phase in the presence of noble metals (Rh, Ru, Pd) as catalysts. Since the H-donor molecules (such as alcohols/ethers and amines (1°, 2°, 3°)) and the acceptor molecules (alkenes (C=C), alkynes (C≡C), and carbonyl (C=O) compounds) play a crucial role from mechanistic viewpoints, the present summary points out the key mechanistic differences with the interpretation of current contributions and the corresponding historical achievements as well.

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“…[3][4][5][6][7][8][9][10][11] All these types of catalysts were based on the presence of ligands forming five membered rings when chelated to the metal centre. Some examples of symmetric 1,4-diamines and few examples of 1,3-diamines were reported in the literature, [12][13][14][15][16][17] mainly used as a typical ruthenium complex [(diphosphine)-RuCl 2 -(diamine)] for hydrogenation of simple aromatic and aliphatic ketones, in the catalytic addition of diethylzinc to aldehyde or in the Cu-catalyzed enantioselective Henry reaction.…”

Section: Introductionmentioning

confidence: 99%

Simple 1,3-diamines and their application as ligands in ruthenium(ii) catalysts for asymmetric transfer hydrogenation of aryl ketones

et al. 2015

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In this research work simple unsymmetrical 1,3-diamines were studied. The synthesis of the diamines started from non-commercial available compounds. S-5a and S,S-5c were obtained by biocatalysis with non conventional yeast, Rhodotorula rubra MIM 147, with excellent 99% e.e. and d.e. up to 90%. Different approaches of synthesis were applied to the same backbone to study both the steric and electronic effects of the ligands. The reactivity of the corresponding ruthenium complexes was evaluated in the asymmetric hydrogen transfer reduction of acetophenone as a standard substrate and of other different aryl ketones, highlighting the flexibility of the six membered chelating ring. A screening of the reaction conditions indicated aqueous media in the presence of HCOONa as a hydrogen donor to be the best system for overcoming the lack of stereocontrol thus allowing us to obtain 56% e.e. in the reduction of acetophenone with the complex in which the ligand was diamine 1, revealed as the best in terms of reactivity and stereoselectivity also in the reduction of the other different aryl ketones, in particular for a-tetralone, i (63% e.e.).

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The importance of 1,2-anti-disubstitution in monotosylated diamine ligands for ruthenium(II)-catalysed asymmetric transfer hydrogenation

Cited by 34 publications

References 47 publications

Artificial metalloenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation

Artificial metalloenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation

Hydrogen Transfer Reactions of Carbonyls, Alkynes, and Alkenes with Noble Metals in the Presence of Alcohols/Ethers and Amines as Hydrogen Donors

Simple 1,3-diamines and their application as ligands in ruthenium(ii) catalysts for asymmetric transfer hydrogenation of aryl ketones

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