Pressure Dependent Highly Enantioselective Hydrogenation of Unsaturated β-Amino Acid Precursors

Heller, Detlef; Holz, Jens; Drexler, Hans‐Joachim; Lang, Jutta; Drauz, Karlheinz; Krimmer, Hans‐Peter; Börner, Armin

doi:10.1021/jo010445l

Cited by 84 publications

(31 citation statements)

References 12 publications

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“…Indeed, interesting results have been obtained with rhodium catalysts containing a bidentate diphosphine ligand such as DuPhos and analogues, [2] Tangphos, [3] BICP, [4] and other optically pure diphosphines.…”

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confidence: 99%

Enantioselective Hydrogenation of β‐Acylamino Acrylates Catalyzed by Rhodium(I)‐Monophosphite Complexes

Jerphagnon

Renaud

Demonchaux³

et al. 2004

Adv Synth Catal

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Chiral rhodium(I) complexes bearing monophosphite ligands, prepared from chiral Binol and (l)-menthol, were found to be efficient catalysts for the asymmetric hydrogenation of b-acylamino acrylates with ee values up to 94%.Keywords: b-acylamino acrylates; enantioselective catalysis; hydrogenation; monophosphite ligands; rhodiumThe preparation of chiral b-amino acid derivatives is an important goal in the pharmaceutical field. They are important building blocks for the synthesis of b-lactams, b-peptide antibiotics and drugs.[1] One of the most attractive and direct pathways to obtain these compounds is the enantioselective hydrogenation of prochiral enamide derivatives with chiral metal complexes. Indeed, interesting results have been obtained with rhodium catalysts containing a bidentate diphosphine ligand such as DuPhos and analogues, [2] Tangphos, [3] BICP, [4] and other optically pure diphosphines.[5]In the last years, increasing attention has been directed to chiral monophosphites, [6] monophosphonites, [7] and monophosphoramidites, [8] due to their ready accessibilities and their efficiency for the hydrogenation of a-dehydroamino acids and itaconic acid derivatives. Very recently, the use of monophosphoramidites for the hydrogenation of (Z)-and (E)-b-acylamino acrylates has been reported, [9] but to our knowledge, no phosphite ligand has been used in the enantioselective hydrogenation of b-acylamino acrylates.We now report the hydrogenation of b-acylamino acrylates catalyzed by rhodium(I)-chiral monophosphite complexes (Scheme 1) and show the crucial role of the binaphthyl moiety in terms of reactivity and enantioselectivity.The monophosphite ligands 1 were synthesized in two steps by treatment of (l)-menthol with 1 equivalent of phosphorus trichloride and triethylamine in tetrahydrofuran followed by addition of 1 equivalent of racemic Binol and 2 equivalents of triethylamine. The phosphite diastereoisomers 1a [(S)-binaphthyl, (l)-menthyl] and 1b [(R)-binaphthyl, (l)-menthyl] were separated by successive recrystallisation in ether, at room temperature and 0 8C, respectively. The prochiral derivatives 2a ± d were prepared by reaction of ammonium acetate with the suitable bketoester followed by acylation of the amino group. [9] This method afforded the acetamidobut-2-enoates 2a ± d as 1 : 1 mixtures of (Z) and (E)-isomers.The hydrogenation reactions were first performed from 2b (0.5 mmol) as a (1 : 1) ethyl (Z/E)-b-acetylaminobut-2-enoate mixture and 1 mol % of complex I (Table 1, Scheme 2).No conversion was observed when the reactions were performed in an apolar solvent such as toluene. In 2-propanol and ethyl acetate, the catalytic system was active but the enantiomeric excesses did not exceed 21% (entries 1 ± 3). The best enantioselectivities and conversions were obtained in dichloromethane (up to 81%, entries 4 ± 9). Under only 3 bars of hydrogen at 50 8C a low conversion was observed (only 4%), but a good enantiomeric excess (81%) was obtained. At the same Scheme 1.

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confidence: 99%

Enantioselective Hydrogenation of β‐Acylamino Acrylates Catalyzed by Rhodium(I)‐Monophosphite Complexes

Jerphagnon

Renaud

Demonchaux³

et al. 2004

Adv Synth Catal

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“…In a parallel work we could show that highly enantioselective hydrogenation of this particular substrate is possible by application of an Rh-DuPHOS catalyst on condition that the reaction was run in a polar solvent like methanol under application of normal hydrogen pressures. [27] This protocol is contrary to the conditions usually recommended in the past for these type of (Z)-configured substrates. In Figure 3 the dependency of the enantioselectivity upon the H 2 pressure by application of [Rh(COD)(13b)]BF 4 is depicted.…”

Section: Enantioselective Hydrogenationsmentioning

confidence: 91%

Synthesis of Chiral 2,5-Bis(oxymethyl)-Functionalized Bis(phospholanes) and Their Application in Rh- and Ru-Catalyzed Enantioselective Hydrogenations

Holz

Stürmer²,

Schmidt

et al. 2001

Eur. J. Org. Chem.

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“…A large number of catalytic systems, especially Rh complexes of chiral diphosphine ligands, have been employed in the hydrogenation of β -dehydroamino acid derivatives. For example, Rh complexes of BPE [122] , DuPhos [122,123] , BasPhos [124,125] , ButiPhane [126] [128] , and 47 [129] as well as Ru complex of BINAP [86] have all been reported to effectively catalyze the hydrogenation of ( E ) -( β -acylamino) acrylates with good enantioselectivities. Rh complexes of TangPhos [36b] , DuanPhos [37] , BINAPINE [130] , 40 [131] , 47 [129] , and 56 [95] are found to be equally or more selective for ( Z ) -( β -acylamino) acrylates.…”

Section: Asymmetric Hydrogenation Of β -Dehydroamino Acidsmentioning

confidence: 99%

Transition Metal‐Catalyzed Homogeneous Asymmetric Hydrogenation

Gao

Zhang

2010

Catalytic Asymmetric Synthesis

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INTRODUCTIONAmong all the catalytic asymmetric methodologies to chiral compounds, homogenous transition metal -catalyzed asymmetric hydrogenation plays a particularly important role [1] . Its highly effi cient, environmental friendly, and cost -effective natures have undoubtly made it one of the most studied methodologies during the past 40 years. As a result, the vast number of catalytic systems developed has also had a signifi cant impact on other areas of asymmetric catalysis [2] . More signifi cantly, the achievements from academia research on asymmetric hydrogenation were frequently acknowledged with industrial applications, which, in turn, provide an important driving force for its basic research [3] .Hundreds of catalytic systems have been developed since the seminal discoveries from Knowles and Sabacky [4] , Kagan and Dang [5] , and Horner et al. [6] . In many cases, series of chiral catalysts were developed based on the similar scaffolds and were prepared for the same reactions. Although these analogous ligands are more likely prepared for the purpose of patent protection other than academic curiosity, they indeed provide us an excellent opportunity to compare, evaluate, and study every aspect of the catalysts in asymmetric hydrogenation. In the meantime, a large number of prochiral unsaturated compounds have been successfully hydrogenated with excellent enantioselectivities. Practical applications with very low catalyst loadings and complex substrate structures have continued to emerge since the publication of the last edition of this book.

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Pressure Dependent Highly Enantioselective Hydrogenation of Unsaturated β-Amino Acid Precursors

Cited by 84 publications

References 12 publications

Enantioselective Hydrogenation of β‐Acylamino Acrylates Catalyzed by Rhodium(I)‐Monophosphite Complexes

Enantioselective Hydrogenation of β‐Acylamino Acrylates Catalyzed by Rhodium(I)‐Monophosphite Complexes

Synthesis of Chiral 2,5-Bis(oxymethyl)-Functionalized Bis(phospholanes) and Their Application in Rh- and Ru-Catalyzed Enantioselective Hydrogenations

Transition Metal‐Catalyzed Homogeneous Asymmetric Hydrogenation

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