Oxygen-Promoted Pd(II) Catalysis for the Coupling of Organoboron Compounds and Olefins

Jung, Young Chun; Mishra, Rajesh; Yoon, Cheol Hwan; Jung, Kyung Woon

doi:10.1021/ol034458s

Cited by 164 publications

(63 citation statements)

References 29 publications

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“…(23)] also proved to be successful nucleophiles. [67] This reaction is insensitive to the electron density on the olefin, as good yields (73-90 %) were obtained for a series of olefins ranging from tert-butyl acrylate to n-butyl vinyl ether.…”

Section: Methodsmentioning

confidence: 98%

Palladium Oxidase Catalysis: Selective Oxidation of Organic Chemicals by Direct Dioxygen‐Coupled Turnover

2004

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Selective aerobic oxidation of organic molecules is a fundamental and practical challenge in modern chemistry. Effective solutions to this problem must overcome the intrinsic reactivity and selectivity challenges posed by the chemistry of molecular oxygen, and they must find application in diverse classes of oxidation reactions. Palladium oxidase catalysis combines the versatility of Pd(II)-mediated oxidation of organic substrates with dioxygen-coupled oxidation of the reduced palladium catalyst to enable a broad range of selective aerobic oxidation reactions. Recent developments revealed that cocatalysts (e.g. Cu(II), polyoxometalates, and benzoquinone) are not essential for efficient oxidation of Pd(0) by molecular oxygen. Oxidatively stable ligands play an important role in these reactions by minimizing catalyst decomposition, promoting the direct reaction between palladium and dioxygen, modulating organic substrate reactivity and permitting asymmetric catalysis.

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Section: Methodsmentioning

confidence: 98%

Palladium Oxidase Catalysis: Selective Oxidation of Organic Chemicals by Direct Dioxygen‐Coupled Turnover

2004

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“…[12] The structure of 3 aa was unequivocally determined by X-ray crystallographic analysis. [13] In the screening of bases, the effect of counter cations clearly stood out with larger cations such as potassium and cesium preferred over sodium (Table 1, entry 1 vs. [2][3][4].…”

Section: Dedicated To Professor Eun Leementioning

confidence: 99%

Stereoselective Synthesis of Highly Substituted Enamides by an Oxidative Heck Reaction

Liu

Park

2011

Angew Chem Int Ed

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The Heck arylation has proven to be among the most versatile reactions for CÀC bond formation owing to its excellent chemoselectivity, wide functional group tolerability, and simplicity.[1] The palladium(0)-mediated catalytic process allows for facile cross-coupling of alkenes with various aryl and heteroaryl halides/pseudohalides. The oxidative Heck reaction has drawn significant attention where arylpalladium(II) species are generated by transmetalation with organometallic counterparts followed by undergoing insertion with alkenes.[2] Among the organometallic coupling partners, organoboronic acids have been extensively explored in various transition-metal-mediated reactions owing to their stability, wide availability, and low toxicity. Since the first demonstration of catalytic, oxidative Heck cross-coupling using arylboronic acids by Cho and Uemura, [2b] significant progress has been made. Despite the recent advances in the field, the limited substrate scope including necessitating steric/electronic bias prompt further improvements. For example, a literature survey shows that examples of Heck cross-coupling with electron-rich alkenes such as enamides are limited to those with simple unsubstituted vinyl groups. [3] b-Amidoacrylate moiety represents an important motif that has been widely utilized as synthetic intermediates in the total synthesis of natural products [4] as well as preparation of heterocycles [5] and b-amino acids through asymmetric hydrogenation.[6] These compounds are typically prepared by condensation of b-ketoesters with amides, [7] and acylation of b-aminoacrylates.[8] Also, transition-metal-mediated reactions have been reported including oxidative amidation of acrylates [9] and addition of amides to terminal alkynes, [10] which typically provide disubstituted enamides. However, the limitations of these reactions include intolerance for sterically demanding substrates. Thus, finding an efficient synthesis of sterically hindered enamides, such as trisubstituted enamides bearing tertiary amides, remains a challenge.In our efforts to develop a synthetic route for the synthesis of structurally diverse b-amino acids, we envisioned that Heck cross-coupling of b-amidoacrylates would provide b-aryl bamidoacrylates which could be subsequently converted into b-amino acid derivatives by asymmetric hydrogenation [Eq. (1)]. Thus, we began by surveying Heck conditions reported in the literature employing 1 a as a substrate (see Table 1 for structure). To our surprise, none of the conditions that we have attempted afforded the Heck products presumably owing to steric and electronic deactivation (see the Supporting Information). Tuning the balance between reactivity and stability of reactants in catalytic reactions is deemed to be among the key factors. The outcomes of the attempted reactions led us to seek the reaction parameters where aryl metal species possess sufficient stability under the reaction conditions, yet activation of which provides the reactivity to participate in the catalytic cycle. Her...

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“…Silver cations then oxidized the Pd (0) to Pd(II) species. 19 In addition, no Michael-type addition product was obtained in the presence of silver cations, despite the addition of the proton source reagent, such as iPrOH and water, in the reaction mixture (Table 1, entries [15][16][17]. When PPh3 was employed as a ligand in this catalytic system, it promoted the homocoupled byproduct (Table 1, entry 11).…”

Section: Notesmentioning

confidence: 99%

“…A variety of solvents were screened. The addition of water and protic solvents such as iPrOH and AcOH showed low product yield, but not Michael-type addition product was found in the reaction mixture (entries [15][16][17][18]. As the temperature decreased to room temperature, the acrylate was not fully converted (entry 19).…”

mentioning

confidence: 99%

“…In addition, we did not detect the byproduct phenol that is derived from the oxidation of phenylboron compound by boron peroxide, which was generated during the catalytic cycle. 17 With the optimized reaction condition selected from Table 1, the coupled reactions with different arylboronic acids and alkenes are presented in Table 2. The Mizoroki-Heck-type coupling products were obtained as major outputs in all cases.…”

mentioning

confidence: 99%

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Ligand-free Palladium-Catalyzed Mizoroki-Heck-type Reaction of Arylboronic Acids and Alkenes Using Silver Cation

Song¹,

Park²,

Oh³

et al. 2010

Bulletin of the Korean Chemical Society

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Transition metal-catalyzed C-C bond formation has been widely used in organic synthesis.1 Among this class of reactions, the coupling reaction using organoboronic acid has been intensively studied due to organoboronic acid's advantages of stability to air and moisture, low toxicity and easy availability. 2One of the most established reactions is Suzuki cross coupling which is the palladium-catalyzed reaction of arylboronic acid and aryl halides.3,4 However, the reaction of arylboronic acid and alkene to afford the Mizoroki-Heck-type product has received less attention, even though this reaction condition is halide free and milder than the original Mizoroki-Heck reaction, which employed aryl halides instead of arylboronic acid. Various new methods have been attempted including a variety of transition metal catalysts (Pd, 5 Ni, 6 Rh,7,8 and Ru 9 ), base-free condition and microwave irradiation.10 When this Mizoroki-Heck-type reaction was carried out with palladium catalyst, nitrogen 11,12 or phosphine-based 13 compounds were generally employed as the ligand. Therefore, ligand-free condition capable of showing high catalytic activity and selectivity is required.It is well established that silver cation can work as an oxidant in the Pd(II) catalytic system. 14 However, there are very few examples of the use of silver cations in the palladium-catalyzed Heck-type reaction of arylboronic acid and alkenes. 15 Here, we report silver cation-mediated Mizoroki-Heck-type reaction to afford the desired product with high yield and high selectivity under ligand-free condition.We selected a standard Mizoroki-Heck-type reaction, with the phenylboronic acid (1a) and the electron-poor olefin n-butyl acrylate (2a), as an appropriate first test reaction. The results are summarized in Table 1. The coupling reactivity was first investigated with a variety of oxidants or bases. We found that the reactivity and selectivity in favor of the desired product 3aa was dependent of the nature of the oxidant or base. Among the oxidants and bases screened, AgOAc afforded the desired product in high yield and with high selectivity (entry 1). Other silver oxidants such as Ag2CO3 and Ag2O gave low yields (entries 2 and 3), while Ag2SO4 or benzoquinone, which is one of the most frequently used oxidants, produced very low yields (entries 4 and 5). The reaction using K3PO4 showed low conversion and afforded a Michael-type addition product as a major one, although at low yield (entry 6). Satoh and Miura reported that K3PO4 afforded a Michael-type addition product as a major output in the presence of phosphite ligand. 16 Carbonate bases afforded a trace amount of the desired product (entries 7-9). When phosphite was employed as a ligand, the reactivity and selectivity were not improved (entry 10). Moreover, triphenylphosphine produced 30% of the byproduct which was derived from the homocoupling of phenylboronic acid (entry 11). All the tested palladium sources showed good yields (entries 1, 12, 13 and 14). A variety of solvents were screened. The ...

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Oxygen-Promoted Pd(II) Catalysis for the Coupling of Organoboron Compounds and Olefins

Cited by 164 publications

References 29 publications

Palladium Oxidase Catalysis: Selective Oxidation of Organic Chemicals by Direct Dioxygen‐Coupled Turnover

Palladium Oxidase Catalysis: Selective Oxidation of Organic Chemicals by Direct Dioxygen‐Coupled Turnover

Stereoselective Synthesis of Highly Substituted Enamides by an Oxidative Heck Reaction

Ligand-free Palladium-Catalyzed Mizoroki-Heck-type Reaction of Arylboronic Acids and Alkenes Using Silver Cation

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