Asymmetric Hydrogenation of 2,4‐Disubstituted 1,5‐Benzodiazepines Using Cationic Ruthenium Diamine Catalysts: An Unusual Achiral Counteranion Induced Reversal of Enantioselectivity

Ding, Ziyuan; Chen, Fei; Qin, Jie; He, Yong; Fan, Qing‐Hua

doi:10.1002/ange.201200309

Cited by 35 publications

(6 citation statements)

References 96 publications

(14 reference statements)

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“…It is obvious that the function of the NH moiety in the ligand shown in Scheme is different from that observed in the ketone hydrogenation (Scheme ). The involvement of the interaction between the NH moiety and the counteranion X − was further shown by 45 ‐catalyzed asymmetric hydrogenation of 1,5‐benzodiazepines 36i. Ruthenium complexes 45 with weakly coordinating anions, such as BArF − , gave R , R ‐products, whereas the catalysts with hydrogen‐bond‐forming anions, such as OTf − and (PhO) 2 PO 2 − induced S , S ‐configuration.…”

Section: Mnh Catalysismentioning

confidence: 96%

“…Recently, Fan and co‐workers demonstrated that η 6 ‐arene/TsDPEN‐Ru II complexes, such as 43 b , 44 , and 45 , were outstanding catalysts for asymmetric hydrogenation of 2‐substituted and 2,3‐disubstituted quinolines,36a,b,d,e 2‐substituted and 2,3‐disubstituted quinoxalines,36f 2,4‐disubstituted 1,5‐benzodiazepines,36i N ‐alkyl ketimines,36g,j cyclic N‐ alkyl imines,36h and cyclic N ‐sulfonylimines,36c affording the corresponding biologically and chemically important chiral amines with excellent enantioselectivities in high yields (Scheme ) 37. Mechanistic studies on the hydrogenations of quinolines revealed that the reduction involves a reaction sequence of 1,4‐hydride addition, isomerization, and 1,2‐hydride addition (Scheme ) 36a,d.…”

Section: Mnh Catalysismentioning

confidence: 99%

“…Ruthenium complexes 45 with weakly coordinating anions, such as BArF − , gave R , R ‐products, whereas the catalysts with hydrogen‐bond‐forming anions, such as OTf − and (PhO) 2 PO 2 − induced S , S ‐configuration. The reversal of enantioselectivity observed in the presence of different counteranions X − (BArF − versus OTf − or (PhO) 2 PO 2 − ) in 45 has been rationalized based on their dramatic changes of the corresponding transition states 36i…”

Section: Mnh Catalysismentioning

confidence: 99%

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The NH Functional Group in Organometallic Catalysis

2013

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The organometallic approach is one of the most active topics in catalysis. The application of NH functionality in organometallic catalysis has become an important and attractive concept in catalyst design. NH moieties in the modifiers of organometallic catalysts have been shown to have various beneficial functions in catalysis by molecular recognition through hydrogen bonding to give catalyst-substrate, ligand-ligand, ligand-catalyst, and catalyst-catalyst interactions. This Review summarizes recent progress in the development of the organometallic catalysts based on the concept of cooperative catalysis by focusing on the NH moiety.

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Section: Mnh Catalysismentioning

confidence: 96%

Section: Mnh Catalysismentioning

confidence: 99%

Section: Mnh Catalysismentioning

confidence: 99%

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The NH Functional Group in Organometallic Catalysis

2013

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“…Although the reduced products represent an important class of chiral heterocycles with pharmacological activity, highly stereoselective reduction of such substrates remains a challenge. 38 Gratifyingly, these dendritic Ir-catalysts exhibited considerable enhancement in activity (Figure 7). In addition, excellent enantioselectivities and good diastereoselectivities, which comparable to those obtained with the small parent catalyst, were achieved by using a dendritic Ir/3c catalyst(Figure 8).…”

Section: Dendritic Phoxmentioning

confidence: 92%

Asymmetric Hydrogenation in the Core of Dendrimers

Fan

2014

Acc. Chem. Res.

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117

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The transition metal complexes containing chiral phosphorus ligands are the most widely and successfully used catalysts in asymmetric hydrogenation of unsaturated compounds. However, a major problem associated with these homogeneous catalytic systems is the separation and recycling of the often expensive and easily oxidized chiral catalysts. In addition, many hydrogenation reactions still lack efficient chiral catalysts, and the stereoselectivities in many hydrogenation reactions are substrate-dependent. Therefore, the development of highly effective and recyclable chiral phosphorus catalysts is highly desirable. Over the past few decades, a number of chiral catalysts have been successfully anchored onto different supports, such as cross-linked polymeric resins and inorganic materials. However, most of the classical supported chiral catalysts suffered from inferior catalytic properties to their homogeneous counterparts due to poor accessibility, random anchoring, and disturbed geometry of the active sites in the solid matrix. To overcome this drawback, dendrimers, which have well-defined and globular macromolecular architectures serve as a promising type of soluble catalyst support. The catalytic sites are generally located at the core or on the periphery of the dendrimer, and the resulting dendritic catalysts are designable. Incorporation of a chiral catalyst into a sterically demanding dendrimer will create a specific microenvironment around the catalytic site and thus influence the catalytic performance of the metal center, like an enzyme does. In this Account, we survey the development of core-functionalized chiral dendritic phosphorus ligands for asymmetric hydrogenation mainly by our research group. Several series of chiral dendritic phosphorus ligands, including diphosphines, monodentate phosphoramidites, and P,N-ligands, have been synthesized by attaching the corresponding chiral phosphorus units into the core or the focal point of Fréchet-type dendrons. Their transition metal (Ru, Rh, or Ir) complexes have been applied in the asymmetric hydrogenation of prochiral olefins and ketones, as well as some challenging imine-type substrates. All reactions were carried out in a homogeneous manner, and the structure-property relationships in some cases were established. The sterically demanding dendritic wedges were found to play important roles in catalytic properties, and better catalytic activities or enantioselectivities or both than those obtained from the corresponding monomeric catalysts were achieved in most cases. In addition, the dendritic catalysts could be readily recycled by means of solvent precipitation, water- or temperature-induced two-phase separation. Our study has thus demonstrated that dendrimer catalysis could combine the advantages of both classical heterogeneous and homogeneous catalysis.

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“…Despite the successful application of asymmetric catalysis to the preparation of a single enantiomer with a certain chiral catalyst, the strategies involving enantiodivergent catalysis that enable dual or reversible enantiocontrol still remain an unexpected and significant challenge. Recently, on the basis of the same chiral ligands or catalysts, great progress has been made by several groups in this context,3–10 for example, reversal of enantioselectivity has been realized by tuning the conformational flexibility of chiral catalysts in asymmetric Michael reaction,3 the addition of zinc metal to an iron complex in the asymmetric hydrosilylation of ketones,4 the use of different metal salt catalysts,5 achiral counteranion‐induced reversal of enantioselectivity in ruthenium‐catalyzed hydrogenation,6 achiral acid‐ or base‐induced switch in the organocatalytic aldol and Mannich reactions,7 chiral anion‐dependent inversion in ruthenium‐catalyzed hydrohydroxyalkylation,8 temperature‐dependent reversal of enantioselectivity in the hydroformylation of styrene,9 and others 10…”

Section: Methodsmentioning

confidence: 99%