Why Is Copper(I) Complex More Competent Than Dirhodium(II) Complex in Catalytic Asymmetric O−H Insertion Reactions? A Computational Study of the Metal Carbenoid O−H Insertion into Water

Liang, Yong; Zhou, Haolai; Yu, Zhi‐Xiang

doi:10.1021/ja9086566

Cited by 226 publications

(208 citation statements)

References 31 publications

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“…The groups of Yu [13] and Platz [14] have reported that either water or alcohols can assist proton transfer in OÀH insertion reactions, as indicated by density functional theory calculations and ultrafast time-resolved IR spectroscopy studies. These studies stimulated our interest in exploring asymmetric N À H insertion in the presence of a proton-transfer catalyst.…”

Section: It Is Generally Accepted That the Rhodium-catalyzed N à H Inmentioning

confidence: 99%

“…The 31 P NMR spectrum of a CDCl 3 solution of (R)-1 h did not change when 0.5 equivalents of [Rh 2 (TPA) 4 ] was introduced at room temperature, thus indicating that there was no coordination of (R)-1 h to rhodium. The addition of 0.5 equivalents of (R)-1 h to a CDCl 3 solution of BocNH 2 had no effect on the 13 C NMR and FTIR signals of the carbonyl group of BocNH 2 . This result implies that the activation of BocNH 2 through the formation of a hydrogen bond with (R)-1 h was unlikely.…”

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confidence: 93%

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Asymmetric NH Insertion Reaction Cooperatively Catalyzed by Rhodium and Chiral Spiro Phosphoric Acids

et al. 2011

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Nitrogen-containing organic compounds, such as a-amino acids and alkaloids, are important biologically active compounds, thus the development of efficient and enantioselective methods for the construction of carbon-nitrogen bonds is a fundamental goal in modern organic synthesis.[1] Transitionmetal-catalyzed carbene insertion into N À H bonds is one of the most efficient methods to construct carbon-nitrogen bonds [2] and the development of asymmetric versions of the NÀH insertion reaction has attracted considerable attention. [3] In initial studies, chiral dirhodium catalysts were tested in intramolecular [4] and intermolecular [5] NÀH insertion reactions, however, only low to modest enantioselectivities (< 50 % ee) were achieved. Since these reports, other transition metals including copper and silver have been used as catalysts, and gave enantioselectivities up to 48 % ee.[6]Recently, we reported a highly enantioselective NÀH insertion reaction (up to 98 % ee) using a copper complex with chiral spiro bisoxazoline ligands.[7] Subsequently, two other types of chiral copper catalysts have been developed, one with a planar chiral bipyridine ligand [8] and the other with a binolderivative ligand, [9] and both of these catalysts give high enantioselectivities in NÀH insertion reactions.Although progress on copper-catalyzed asymmetric NÀH insertion reactions has been substantial, they still have serious limitations. For instance, all the copper-catalyzed N À H insertion reactions require high catalyst loading (5-10 mol %) for satisfactory yields and enantioselectivities, thus more-efficient chiral catalysts are highly desirable. Because the activity of dirhodium(II) catalysts is usually superior to that of copper catalysts in nonenantioselective NÀ H insertion reactions, [10] the possibility of using dirhodium catalysts to achieve highly enantioselective N À H insertion reactions is an intriguing one. Recently, Saito et al. [11] reported that dirhodium(II) carboxylates and cinchona alkaloids cooperatively catalyze the asymmetric NÀH insertion reactions of a-diazo-a-arylacetates with anilines. The combined catalysts exhibit excellent reactivity but only modest enantioselectivity (up to 71 % ee). It is generally accepted that the rhodium-catalyzed N À H insertion most likely proceeds via an ylide intermediate (Scheme 1 A).[2a] We speculated that the subsequent protontransfer step could be facilitated by a chiral phosphoric acid [12] species via a seven-membered-ring transition state, and that, consequently, chiral induction could be accomplished in this step (Scheme 1 B). The groups of Yu [13] and Platz [14] have reported that either water or alcohols can assist proton transfer in OÀH insertion reactions, as indicated by density functional theory calculations and ultrafast time-resolved IR spectroscopy studies. These studies stimulated our interest in exploring asymmetric N À H insertion in the presence of a proton-transfer catalyst. As part of our ongoing work on the development of asymmetric carbene insertion reaction...

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Section: It Is Generally Accepted That the Rhodium-catalyzed N à H Inmentioning

confidence: 99%

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confidence: 93%

Asymmetric NH Insertion Reaction Cooperatively Catalyzed by Rhodium and Chiral Spiro Phosphoric Acids

et al. 2011

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“…A reasonably low transition state barrier would require the H δ+ to reach the electron lone pair of N of the imine arm. Proton-transfer (H-transfer) shuttles were recently identified in facilitating various H-transfer processes in related reactions [58,[97][98][99][100][101][102][103][104][105][106][107][108]. The mediating agents for the H-transfer process can be protonic solvent molecules (alcohols and water), substrates, or products.…”

Section: 23mentioning

confidence: 99%

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

Zheng

Huang

2015

Coordination Chemistry Reviews

177

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“…[4][5][6][7][8][9] However, only limited success has been achieved for asymmetric insertions into O-H bond. 2,[10][11][12] Recently, Fu and Zhou independently reported asymmetric insertion reactions into alcoholic, 13) phenolic 14) and aquatic 15) O-H bonds with a-diazoacetate using chiral Cu(I) complexes. In contrast, chiral Rh(II) complexes gave poor enantioselectivity (8% ee) in the O-H insertion reaction, 11) while they have given remarkable results in the C-H insertion reaction.…”

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confidence: 99%

“…10) They concluded that Rh(II) complex does not have enough affinity to the oxonium ylide intermediate to form firmly fixed stereocenter around the metal. Hence, we sought to design a novel approach to the enantioselective O-H insertion reaction catalyzed by Rh(II) complexes, independent of its own chirality.…”

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Chiral Induction by Cinchona Alkaloids in the Rhodium(II) Catalyzed O-H Insertion Reaction

et al. 2010

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The catalytic insertion reaction into O-H bond with a-diazocarbonyl compounds via a metal-carbenoid intermediate is a very useful organic transformation for the synthesis of oxygen-containing compounds.1-3) Remarkable advances, including enantioselective insertion, have been made in catalytic C-H insertions with a-diazocarbonyl compounds using Rh(II) complexes. [4][5][6][7][8][9] However, only limited success has been achieved for asymmetric insertions into O-H bond. 2,[10][11][12] Recently, Fu and Zhou independently reported asymmetric insertion reactions into alcoholic, 13) phenolic 14) and aquatic 15) O-H bonds with a-diazoacetate using chiral Cu(I) complexes. In contrast, chiral Rh(II) complexes gave poor enantioselectivity (8% ee) in the O-H insertion reaction, 11) while they have given remarkable results in the C-H insertion reaction. Since Rh(II) complexes are unique and powerful catalysts in the insertion reaction, we attempted to apply them to the enantioselective O-H insertion reaction.Recently, Liang et al. conducted a physicochemical approach to O-H insertion reactions using density functional theory (DFT). 10) They concluded that Rh(II) complex does not have enough affinity to the oxonium ylide intermediate to form firmly fixed stereocenter around the metal. Hence, we sought to design a novel approach to the enantioselective O-H insertion reaction catalyzed by Rh(II) complexes, independent of its own chirality. It is of interest that chiral amine additives expressed its own chirality on metal mediated epoxidation reaction using achiral Mn-salen complex. 16)Accordingly, we envisaged that an intermolecular O-H insertion of a-aryldiazoacetate and water should produce a mandelate in an enantioselective manner using cinchona alkaloids and Rh(II) complexes. Using this method, we now report that a combination of quinine (1) or quinidine (2) and dirhodium(II) tetra(triphenylacetate), Rh 2 (TPA) 4 , in the O-H insertion provides mandelate as the sole product in up to 50% ee.In our initial studies, we explored the intermolecular O-H insertion of methyl phenydiazoacetate in dichloromethane using 1 mol% of Rh 2 (TPA) 4 17,18) and 2 mol% of quinine (1) (Table 1, entry 1). [19][20][21][22] As expected, the reaction proceeded smoothly at 23°C to completion within 4 h, giving methyl mandelate in 82% yield. The enantioselectivity in this reaction was 38% ee, as determined by HPLC (Daicel Chiralcel OD-H). The preferred absolute stereochemistry was (S), which was established by comparing the sign of the optical rotation with the literature value.23) It is worth noting that enantioselectivity for a particular product was provided by the cinchona alkaloids, not by the rhodium catalyst. The enantiomeric induction in this system may be due to the formation of a chiral complex between rhodium-carbenenoid and cinchona alkaoid. To rule out the possibility that the reaction was catalyzed by quinine (1), we performed the reaction under identical conditions in the absence of Rh 2 (TPA) 4 and observed no background reaction. To ...

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Why Is Copper(I) Complex More Competent Than Dirhodium(II) Complex in Catalytic Asymmetric O−H Insertion Reactions? A Computational Study of the Metal Carbenoid O−H Insertion into Water

Cited by 226 publications

References 31 publications

Asymmetric NH Insertion Reaction Cooperatively Catalyzed by Rhodium and Chiral Spiro Phosphoric Acids

Asymmetric NH Insertion Reaction Cooperatively Catalyzed by Rhodium and Chiral Spiro Phosphoric Acids

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

Chiral Induction by Cinchona Alkaloids in the Rhodium(II) Catalyzed O-H Insertion Reaction

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