Carbon-carbon bond formations promoted by transition metal carbonyls. III. Mechanistic aspects of the reaction of .alpha.,.alpha.1-dibromo ketones and iron carbonyl. Reductive rearrangements of dibromo ketones

Noyori, Ryoji; Hayakawa, Yoshihiro; Funakura, M.; Takaya, Hidemasa; Murai, Shinji; Kobayashi, Ryoichi; Tsutsumi, Shigeru

doi:10.1021/ja00775a084

Cited by 46 publications

(6 citation statements)

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“… Due to the thermally forbidden nature of the uncatalyzed concerted (3+2) cycloaddition pathway, however, it has proven much more difficult to leverage the synthetic potential of oxyallyl cations for the construction of five-membered rings . Prior to Trost’s work, only a limited number of stepwise (3+2) cycloadditions employing stoichiometric metal-based reagents were reported. − …”

Section: Introductionmentioning

confidence: 99%

Origins of Selective Formation of 5-Vinyl-2-methylene Furans from Oxyallyl/Diene (3+2) Cycloadditions with Pd(0) Catalysis

2019

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The (3+2) cycloadditions between electron-deficient Pd-oxyallyls and conjugated dienes have been investigated with density functional theory calculations. A stepwise mechanism with C–C bond formation occurring first is supported by computations. The key electron-withdrawing ester substituent on the Pd-oxyallyl species decreases the migratory insertion barrier by both lowering the LUMO energy and enabling a less-strained six-membered coordination mode. The lack of (3+2) reactivity with monoenes is attributed to higher migratory insertion barriers due to a lower-energy HOMO, as well as high C–O reductive elimination barriers, which become rate-determining. Conjugated dienes enable the formation of a highly electrophilic η3 Pd-allyl species and greatly facilitates C–O formation.

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Section: Introductionmentioning

confidence: 99%

Origins of Selective Formation of 5-Vinyl-2-methylene Furans from Oxyallyl/Diene (3+2) Cycloadditions with Pd(0) Catalysis

2019

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“…The underdevelopment of (3+2) cycloaddition with the oxyallyl cation is largely attributed to the forbidden concerted pathway due to unmatched frontier molecular orbitals, and only a limited number of reactions that operate through stepwise mechanisms have been developed to date (5). For example, Noyori and co-workers have pioneered the (3+2) cycloaddition between styrene-or enamine-type olefins with a,a′-dihaloketones to cyclopentanone derivatives by using low-valent iron carbonyl as the reductant (6)(7)(8). A similar cyclopentanone synthesis has also been achieved by the Kuwajima group, with electron-rich olefins, where the oxyallyl cation was generated with aluminum-based Lewis acids from a-acetoxy silyl enol ether (9).…”

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confidence: 99%

Catalytic palladium-oxyallyl cycloaddition

Trost

Huang

Murhade

2018

Science

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Exploration of intermediates that enable chemoselective cycloaddition reactions and expeditious construction of fused- or bridged-ring systems is a continuous challenge for organic synthesis. As an intermediate of interest, the oxyallyl cation has been harnessed to synthesize architectures containing seven-membered rings via (4+3) cycloaddition. However, its potential to access five-membered skeletons is underdeveloped, largely due to the thermally forbidden (3+2) pathway. Here, the combination of a tailored precursor and a Pd(0) catalyst generates a Pd-oxyallyl intermediate that cyclizes with conjugated dienes to produce a diverse array of tetrahydrofuran skeletons. The cycloaddition overrides conventional (4+3) selectivity by proceeding through a stepwise pathway involving a Pd-allyl transfer and ring closure sequence. Subsequent treatment of the (3+2) adducts with a palladium catalyst converts the heterocycles to the carbocyclic cyclopentanones.

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“…rota BC no esquema 17) 8,9 . A utilização de Fe 2 (CO) 9 para gerar cátions oxialílicos a partir de α,α'-dibromocetonas e α,α,α',α'-tetrabromocetonas foi desenvolvida por Noyori et alii 19,20,[38][39][40] . Este reagente pode ser utilizado com uma grande variedade de polibromocetonas, e dienos cíclicos (Esquema 7) e acíclicos.…”

Section: Obtenção De Cátions Oxialílicos a Partir De α-Halocetonasunclassified

Cicloadições [3+4] via cátions oxialílicos: aplicações em sínteses orgânicas

Demuner¹,

Barbosa²,

Piló‐Veloso³

1997

Quím. Nova

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Em seu experimento clássico, Fort 3-5 tratou 1-cloro-1,3-difenilpropanona (1), furano e 2,6-lutidina em DMF, obtendo uma mistura isomérica dos cicloadutos 2a e 2b. Quando essa reação foi repetida em presença de metanol, obteve-se somente o produto 3, proveniente da substituição do cloro da cetona 1 (Esquema 1). Fort realizou o estudo da cinética dessa metanó-lise e verificou que, neste caso, a formação do composto 3 ocorre através do intermediário 4, o qual pode ser originado a partir do cátion oxialílico 5, conforme ilustrado no esquema 2. Esquema 1 Esquema 2Mais tarde, Cookson et alii 6,7 desenvolveram outro procedimento mais eficiente para o preparo dos oxabiciclos 2a e 2b através da redução da α,α'-dibromocetona 6 com NaI, na presença de furano (Esquema 3). Neste caso foi observada a formação de grande quantidade da furilcetona 2c, resultante da reação de substituição eletrofílica entre o furano e o cátion oxialílico gerado in situ.Para avaliar a generalidade desta cicloadição Cookson et alii 7 realizaram experimentos com ciclopentadieno e Nmetilpirrol cujos resultados (compostos 7a-b e 8) são mostrados no esquema 3. No caso do N-metilpirrol apenas o produto da substituição eletrofílica 8 foi isolado.Em termos eletrônicos, de acordo com as regras de Woodward-Hoffmann, essa reação é uma cicloadição iônica do

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Carbon-carbon bond formations promoted by transition metal carbonyls. III. Mechanistic aspects of the reaction of .alpha.,.alpha.1-dibromo ketones and iron carbonyl. Reductive rearrangements of dibromo ketones

Cited by 46 publications

References 0 publications

Origins of Selective Formation of 5-Vinyl-2-methylene Furans from Oxyallyl/Diene (3+2) Cycloadditions with Pd(0) Catalysis

Origins of Selective Formation of 5-Vinyl-2-methylene Furans from Oxyallyl/Diene (3+2) Cycloadditions with Pd(0) Catalysis

Catalytic palladium-oxyallyl cycloaddition

Cicloadições [3+4] via cátions oxialílicos: aplicações em sínteses orgânicas

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