Catalysts with Mixed Ligands on Immobilized Supports. Electronic and Steric Advantages

Doyle, Michael P.; Yan, Ming; Gau, Han Mou; Blossey, Erich C.

doi:10.1021/ol027475a

Cited by 61 publications

(23 citation statements)

References 20 publications

(19 reference statements)

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“…15.2) [40,41]. Both Novasyn and Merrifield resins proved effective, and mixed ligand systems with enhanced electronic and steric characteristics could be produced by this methodology [41]. …”

Section: Catalytic Asymmetric Cyclopropanation and Cyclopropenationmentioning

confidence: 97%

“…These chiral catalysts have also been linked to polymeric resins (Equation (7)) for multiple use/reuse without significant loss in enantiocontrol (Fig. 15.2) [40,41]. Both Novasyn and Merrifield resins proved effective, and mixed ligand systems with enhanced electronic and steric characteristics could be produced by this methodology [41].…”

Section: Catalytic Asymmetric Cyclopropanation and Cyclopropenationmentioning

confidence: 99%

See 1 more Smart Citation

Chiral Dirhodium(II) Carboxamidates for Asymmetric Cyclopropanation and Carbon–Hydrogen Insertion Reactions

Doyle

2005

Modern Rhodium‐Catalyzed Organic Reactions

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In 1989-1990 three groups published initial results relating to the development of dirhodium(II) catalysts for asymmetric transformations of diazo compounds [1][2][3]. Two focused on amino acid carboxylate ligands [1,2], and one of them fortuitously found that prolinate ligands had unusual selectivity in reactions of diazoacetates and related substrates [2], even though the ligand's chiral centers lie far from the axial sites of dirhodium(II), which is where the carbene intermediate is formed. This discovery has led to very significant undertakings by Davies, particularly with aryl-and vinyldiazoacetates [4-8], but they have already been described in Chapter 14.On the basis of reports by Bear and co-workers [10-12] and the discovery that carboxamidate ligands could be introduced onto dirhodium(II) by semi-automated methods [13], Doyle and co-workers began their development of carboxamidate ligands for dirhodium with oxazolidinones (for example, 1 and 2), but with limited success in achieving high enantiocontrol [3]. Only when a carboxylate attachment, as in pyrrolidinone 3, rather than an isopropyl or benzyl group, as in 1 or 2, was placed in proximity to the reaction center, could high enantiocontrol be achieved [14]. The key developments here were: 1) the methodology for the semi-automated synthesis of dirhodium(II) carboxamidates by trapping acetic acid with sodium carbonate in a Soxhlet extraction apparatus (Eq. 1) [15]; and 2) the discovery of the high selectivity enhancement afforded by the carboxylate attachment [16]. Scheme 15.6 (cont.) Scheme 15.7 Synthesis of 2-deoxyxylolactone. 93 : 7

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Section: Catalytic Asymmetric Cyclopropanation and Cyclopropenationmentioning

confidence: 97%

Section: Catalytic Asymmetric Cyclopropanation and Cyclopropenationmentioning

confidence: 99%

Chiral Dirhodium(II) Carboxamidates for Asymmetric Cyclopropanation and Carbon–Hydrogen Insertion Reactions

Doyle

2005

Modern Rhodium‐Catalyzed Organic Reactions

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“…This strategy was used in the replacement of one of the ligands of Rh 2 (5S-MEPY) 4 , Rh 2 (4S-MPPIM) 4 , Rh 2 (4S-MEAZ) 4 , and Rh 2 (4S-IBAZ) 4 . 25 The synthesised metal-anchored polymers were reported to be active catalysts towards cyclopropanation and intramolecular C-H insertion showing comparable yields but lower enantioselectivities to those of homogeneous catalysts (Table 3). In the intramolecular cyclopropanation of the phenyldiazo acetate derivative 14, the polymer was recovered and reused through four cycles keeping the same yields and selectivities.…”

Section: Covalent Binding By Bridging Ligandmentioning

confidence: 99%

Making expensive dirhodium(ii) catalysts cheaper: Rh(ii) recycling methods

2012

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Dirhodium(II) catalysts have been widely used as a remarkable tool in organic synthesis, ultimately resulting in a myriad of transformations and formation of a wide variety of compounds, every so often intermediaries in drug synthesis. Aiming at a more sustainable chemistry, several methods suitable for the reutilisation of expensive dirhodium complexes have been developed. Herein, we provide a combined overview of the available methods for recovering and reusing dirhodium(II) metal complexes in catalysis, covering homogeneous catalysis as well as heterogenisation methods.

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“…Accordingly, the synthesis and heterogenization of chiral dirhodium (II) complexes is currently a very active research field. A number of strategies for the heterogenization of chiral dirhodium catalysts such as forming covalent bonds via bidentate [48][49][50][51][52] or axial [53][54][55][56] binding were proposed. These heterogeneous catalysts were then successfully used in various asymmetric reactions.…”

Section: Introductionmentioning

confidence: 99%

Dirhodium Coordination Polymers for Asymmetric Cyclopropanation of Diazooxindoles with Olefins: Synthesis and Spectroscopic Analysis

Rösler

Herr

et al. 2020

ChemPlusChem

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A facile approach is reported for the preparation of dirhodium coordination polymers [Rh2(L1)2]n (Rh2‐L1) and [Rh2(L2)2]n (Rh2‐L2; L1=N,N’‐(pyromellitoyl)‐bis‐L‐phenylalanine diacid anion, L2=bis‐N,N’‐(L‐phenylalanyl) naphthalene‐1,4,5,8‐tetracarboxylate diimide) from chiral dicarboxylic acids by ligand exchange. Multiple techniques including FTIR, XPS, and 1H→13C CP MAS NMR spectroscopy reveal the formation of the coordination polymers. 19F MAS NMR was utilized to investigate the remaining TFA groups in the obtained coordination polymers, and demonstrated near‐quantitative ligand exchange. DR‐UV‐vis and XPS confirm the oxidation state of the Rh center and that the Rh‐single bond in the dirhodium node is maintained in the synthesis of Rh2‐L1 and Rh2‐L2. Both coordination polymers exhibit excellent catalytic performance in the asymmetric cyclopropanation reaction between styrene and diazooxindole. The catalysts can be easily recycled and reused without significant reduction in their catalytic efficiency.

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Catalysts with Mixed Ligands on Immobilized Supports. Electronic and Steric Advantages

Abstract: [reaction: see text] Immobilized dirhodium(II) catalysts having mixed chiral ligands enhance reactivity (AH = azetidinone) and influence stereoselectivity in cyclopropanation and carbon-hydrogen insertion reactions.

Cited by 61 publications

References 20 publications

Chiral Dirhodium(II) Carboxamidates for Asymmetric Cyclopropanation and Carbon–Hydrogen Insertion Reactions

Chiral Dirhodium(II) Carboxamidates for Asymmetric Cyclopropanation and Carbon–Hydrogen Insertion Reactions

Making expensive dirhodium(ii) catalysts cheaper: Rh(ii) recycling methods

Dirhodium Coordination Polymers for Asymmetric Cyclopropanation of Diazooxindoles with Olefins: Synthesis and Spectroscopic Analysis

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