Palladium-catalyzed asymmetric arylation of 2,3-dihydrofuran with phenyl triflate. A novel asymmetric catalysis involving a kinetic resolution process

Ozawa, Fumiyuki; Kubo, A.; Matsumoto, Y.; Hayashi, Tamio; Nishioka, Eriko; Yanagi, Kazunori; Moriguchi, Kohichi

doi:10.1021/om00034a064

Cited by 273 publications

(167 citation statements)

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“…The ligands (R)-8a-c were classified to bear Pr-chirality by comparison with (R)-or (S)-BINAP, whose metal complexes had been structurally resolved by X-ray crystallography. 26,27) Based on our previous elucidation of the correlation between the Pr/Mr chirality of ligands and the hydrogenation products, 24,25) it is reasonable that Pr-chirality ligands show R-and S-selectivities in the hydrogenation of itaconic acids and (Z)-a-acetamidocinnamic acid, respectively. Therefore, the ligands (R)-8b, c have normal selectivity in the rhodium-catalyzed hydrogenation.…”

Section: Resultsmentioning

confidence: 98%

Preparation of Axially Chiral Biphenyl Diphosphine Ligands and Their Application in Asymmetric Hydrogenation

Morimoto

Yoshikawa

Murata

et al. 2004

CHEMICAL & PHARMACEUTICAL BULLETIN

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Development of efficient methods for catalytic enantioselective synthesis has been an important subject for the practical synthesis of optically active organic compounds.1) Numerous methods of enantioselective synthesis employing various catalysts such as transition metal complexes coordinated with many types of chiral ligands have been reported for more than three decades. [1][2][3][4][5][6] For the development of efficient chiral catalysts, creation of new types of ligands is a most significant strategy. Among various types of chiral ligands, diphosphines are the most effective and are widely applicable in the catalytic asymmetric hydrogenation of prochiral compounds such as olefins, ketones, and imines using transition metal (rhodium, ruthenium, iridium, etc.) complexes as catalyst. We previously proposed a novel idea, "respective control concept" for designing new chiral ligands, 7-10) and developed efficient diphosphine ligands such as (2S-cis)-4-(dicyclohexylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinecarboxylic acid 1,1-dimethylethyl ester (BCPM) and its analogs, 8,[11][12][13] (4R-trans)-[(2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(methylene)]bis[bis(4-methoxy-3,5-dimethylphenyl)phosphine] (MOD-DIOP) and its analogs, [14][15][16][17] etc. (Fig. 1) for rhodium-catalyzed asymmetric hydrogenation of some prochiral ketones (ketopantolactone, a-and bamino ketones, etc.), and olefins (itaconic acid and its derivatives, N-acyldehydroamino acids, etc.). Furthermore, we revealed that phosphines bearing electron-donating groups such as cyclohexyl groups, p-(dimethylamino)phenyl groups, and p-methoxy-m,mЈ-dimethylphenyl groups enhance not only the catalytic activity but also the enantioselectivity in the rhodium-catalyzed hydrogenations. The p-methoxym,mЈ-dimethylphenyl (abbreviated to MOD) group was found to be a useful component for developing efficient ligands on the basis of its steric effect (m-Me) as well as its electronic effect (p-MeO, m-Me).15) We also reported in preliminary communications the design and preparation of axially chiral diphosphines, [18][19][20][21] which were found to be very efficient ligands for ruthenium-catalyzed asymmetric hydrogenation of a b-keto ester or rhodium-catalyzed asymmetric hydrogenation of an a-amino ketone. In this article we describe in detail the synthesis of optically pure 3,3Ј-dimethoxy-2,2Ј,4,4Ј-tetramethyl-1,1Ј-biphenyls 8a-c bearing one or two 6,(6Ј)-dicyclohexylphosphino group(s) and/or 6,(6Ј)-diphenylphosphino group(s), and an application to rhodium-catalyzed asymmetric hydrogenation. Results and DiscussionThe synthetic route of axially dissymmetric biphenyldiphosphine ligands 8a-c bearing one or two dicyclohexylphosphino group(s) and/or one or two diphenylphosphino group(s) is described in Chart 1 (8a-c were abbreviated to BIMOP, Cy-BIMOP, and MOC-BIMOP, respectively). Iodination of 2,6-dimethylnitrobenzene (1) was carried out selectively at the 3-position by heating with iodine at 90°C for 4 d in the presence of periodic acid in acetic acid containing d...

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Section: Resultsmentioning

confidence: 98%

Preparation of Axially Chiral Biphenyl Diphosphine Ligands and Their Application in Asymmetric Hydrogenation

Morimoto

Yoshikawa

Murata

et al. 2004

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…The early work of Hayashi has provided a benchmark that has rarely been surpassed. [5] To summarise briefly, phenylation of 2,3-dihydrofuran catalysed by Pd(OAc) 2 , BINAP and base gives rise to two distinct products, the direct elimination product and that of further isomerisation, as shown (Scheme 2). The interplay between these two products can lead to enhanced enantioselectivity by kinetic resolution; generally speaking, the less of the isomerised product is formed the higher the ee.…”

Section: Introductionmentioning

confidence: 99%

Conformationally Restricted Arene Intermediates in the Intermolecular Heck Arylation of Vinylarenes

et al. 2004

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In appreciation of a fruitful collaboration with Jo Bargon, on the occasion of his 65 th birthday. Abstract:The NMR observation of s-benzylpalladium intermediates at low temperature, formed by reaction of arylpalladium diphosphine cations with simple vinylarenes, indicates restricted rotation in the adjacent aryl ring. The stability of the intermediate is greater in the dppp than in the dppf series. By a combination of NMR techniques, it was possible to characterise the intermediate, and to consider permissible structures.

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“…This intermediate is then hydrated to generate acyclic oxypalladation intermediate B in which the oxygen from water is incorporated into the amide carbonyl. Intermediate B reacts with an alkene substrate through a Hecklike process 10 resulting in Pd-alkyl species C. -Hydride elimination generates a Pd-alkene complex such as D and sequential olefin insertion--hydride elimination steps result in migration of the olefin to the R, position in E. 11 Release of R, -unsaturated ketone product followed by reductive elimination results in Pd(0), which is oxidized to regenerate Pd(II).…”

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confidence: 99%

Synthesis of Acyclic α,β-Unsaturated Ketones via Pd(II)-Catalyzed Intermolecular Reaction of Alkynamides and Alkenes

2007

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Transition-metal-catalyzed reactions of alkynes with alkenes have proven to be reliable and important strategies for carbon-carbon bond formation. 1 Previous efforts have focused primarily on nonoxidative reactions such as isomerizations of enynes to synthesize cyclic dienes and cyclopropyl derivatives, 1a-g or cross-metathesis to synthesize acyclic dienes. 1e,h Extending alkyne-alkene reactivity to include oxidative couplings 2 could provide convenient access to additional organic functionality. We recently used DNA-templated synthesis and in vitro selection to discover a Pd(II)-mediated alkyne-alkene cyclization reaction that generates a macrocyclic R, -unsaturated ketone. 3 Here we describe the development of an analogous intermolecular oxidative coupling reaction between alkynamides and terminal alkenes to generate acyclic R, -unsaturated ketones 4 (eq 1). Our results reveal that amides can mediate this mode of alkyne reactivity and provide efficient access to acyclic R, -unsaturated ketones under very mild conditions.We began the development of this reaction by defining its basic requirements with respect to the alkyne substrate and the reaction conditions. Several alkynes were examined for their ability to react with styrene in the presence of various palladium salts. We discovered that alkynamides possessing a pentyn-or hexynamide backbone were required for efficient R, -unsaturated ketone formation (Table 1). For example, slow addition of N-benzyl-Nmethylpent-4-ynamide to a mixture of 1.5 equiv of styrene and 1.0 equiv of Na 2 PdCl 4 in MeCN-H 2 O (3:2) at room temperature provided the E-R, unsaturated ketone product in 53% isolated yield (Table 1, entry 4), whereas the analogous propyn-, butyn-and heptynamide substrates did not generate significant desired product under these conditions (Table 1, entries 2 and 8). Furthermore, no R, -unsaturated ketone was observed when water was omitted from the reaction (Table 1, entry 3). The use of p-benzoquinone as a stoichiometric oxidant enabled multiple turnovers with 0.2 equiv of Pd(II) to provide enone products in 54-58% yield (Table 1, entry 6 and 7).On the basis of the requirement for a pentynamide or hexynamide backbone, we hypothesized that R, -unsaturated ketone formation proceeds through a cyclic oxypalladation intermediate. 5 To test this proposal, we performed an 17 O labeling experiment. When the reaction between N-benzyl-N-methylpent-4-ynamide (1) and styrene was conducted in MeCN-17 OH 2 (3:2), 17 O NMR revealed the presence of broad peak at 318.5 ppm that is characteristic of an amide Cd 17 O (eq 2) but inconsistent with an enone Cd 17 O (eq 3). 6 This result strongly suggests that the reaction proceeds through a cyclic oxypalladation intermediate (eq 2), rather than through an acyclic intermediate that would result from the direct hydration of a Pd(II)-alkyne complex (eq 3). 7The scope of the reaction was further examined under optimized conditions using 0.15 equiv of Na 2 PdCl 4 , 0.2 equiv of CuCl 2 , and molecular oxygen as the terminal oxidan...

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Palladium-catalyzed asymmetric arylation of 2,3-dihydrofuran with phenyl triflate. A novel asymmetric catalysis involving a kinetic resolution process

Cited by 273 publications

References 0 publications

Preparation of Axially Chiral Biphenyl Diphosphine Ligands and Their Application in Asymmetric Hydrogenation

Preparation of Axially Chiral Biphenyl Diphosphine Ligands and Their Application in Asymmetric Hydrogenation

Conformationally Restricted Arene Intermediates in the Intermolecular Heck Arylation of Vinylarenes

Synthesis of Acyclic α,β-Unsaturated Ketones via Pd(II)-Catalyzed Intermolecular Reaction of Alkynamides and Alkenes

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