Cooperative Catalysis with Chiral Brønsted Acid-Rh<sub>2</sub>(OAc)<sub>4</sub>: Highly Enantioselective Three-Component Reactions of Diazo Compounds with Alcohols and Imines

Hu, Wenhao; Xu, Xinfang; Zhou, Jing; Liu, Weijun; Huang, Haoxi; Hu, Juan; Yang, Liping; Gong, Liu‐Zhu

doi:10.1021/ja801755z

Cited by 357 publications

(74 citation statements)

References 41 publications

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“…The system differs from previously reported binary systems because of the isolobal analogy of the proton and [LAu I ] cations. [17,18] Although some mechanistic details are still unexplored, synthetically this concept allows access to various efficient enantioselective one-pot cascade reactions. By now the significance of this new concept has been demonstrated by a number of follow-up publications: Another example of a hydroamination/hydrogenation cascade reaction was provided by Liu and Che.…”

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confidence: 99%

Gold and Organocatalysis Combined

2010

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mentioning

confidence: 99%

Gold and Organocatalysis Combined

2010

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“…[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).…”

Section: )mentioning

confidence: 72%

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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“…In an example (Scheme 12) reported by Hu, Gong, and co-workers, rhodium(II) activated a diazoalkane 35, and the intermediate rhodium carbene first underwent OÀH insertion with an alcohol, followed by addition of a (putative) oxonium ylide to a chiral nonracemic iminium salt 34·36. [48] The overall reaction yielded an antiglycolate Mannich product 37 with high diastereo-and enantioselectivity. The level of rate control inherent to this transformation is more remarkable when considering the low concentration of the two catalysts (each < 2 mol %) working cooperatively to activate separate reactants according to the proposed mechanism.…”

Section: Diazoalkane Activation Using Brønsted Acid Co-catalysismentioning

confidence: 96%

To Protonate or Alkylate? Stereoselective Brønsted Acid Catalysis of CC Bond Formation Using Diazoalkanes

2010

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A new means to activate diazoalkanes has been discovered and applied broadly over the past few years. Brønsted acids, both achiral and chiral, have been used to promote the formation of carbon-carbon and carbon-heteroatom bonds with a growing number of diazoalkane derivatives. Aside from their straightforward ability to build structural and stereochemical complexity in innovative new ways, these transformations are remarkable owing to their ability to skirt competitive diazo protonation--a reaction that has long been used to prepare esters efficiently and cleanly from carboxylic acids. In cases where achiral Brønsted acids are used, high diastereoselection can be achieved. Meanwhile, chiral Brønsted acids can deliver products with both high diastereo- and enantioselectivity. More recently, systems have emerged that combine Brønsted acids and either Lewis acids or transition metals to promote carbon-carbon bond formation from diazoalkanes.

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Cooperative Catalysis with Chiral Brønsted Acid-Rh₂(OAc)₄: Highly Enantioselective Three-Component Reactions of Diazo Compounds with Alcohols and Imines

Cited by 357 publications

References 41 publications

Gold and Organocatalysis Combined

Gold and Organocatalysis Combined

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

To Protonate or Alkylate? Stereoselective Brønsted Acid Catalysis of CC Bond Formation Using Diazoalkanes

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Cooperative Catalysis with Chiral Brønsted Acid-Rh2(OAc)4: Highly Enantioselective Three-Component Reactions of Diazo Compounds with Alcohols and Imines

Cited by 357 publications

References 41 publications

Gold and Organocatalysis Combined

Gold and Organocatalysis Combined

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

To Protonate or Alkylate? Stereoselective Brønsted Acid Catalysis of CC Bond Formation Using Diazoalkanes

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Cooperative Catalysis with Chiral Brønsted Acid-Rh₂(OAc)₄: Highly Enantioselective Three-Component Reactions of Diazo Compounds with Alcohols and Imines