Reaktivität und Selektivität bei der Oxidation von Styrolderivaten. V. Untersuchungen zur Oxidation vonα-substituierten Styrolen

Suprun, Wladimir

doi:10.1002/(sici)1521-3897(199901)341:1<52::aid-prac52>3.0.co;2-d

Cited by 8 publications

(1 citation statement)

References 37 publications

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“…Furthermore, while 1 O 2 reacts preferentially with electron-rich olefins to furnish dioxetane species that can facilely cleave, affording carbonyl compounds, Fe(OTf) 3 -L1 promotes the aerobic cleavage of both electron-deficient and -rich styrenes with high yields (Table ). Still further, allylic hydroperoxides were reported as main products from the 1 O 2 mediated cleavage of cyclopropyl-substituted olefins , and the photooxidation of 3g furnished a distribution of products with 4g being obtained as a minor product; in contrast, the Fe(OTf) 3 - L4 -catalyzed oxidation of 3g afforded 4g as the sole reaction product (Table ). Additionally, the introduction of β-carotene, an inhibitor of 1 O 2 , did not affected the oxidation of styrene 1b to benzaldehyde (eq 5).…”

Section: Results and Discussionmentioning

confidence: 99%

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂

2015

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A mild and operationally simple iron-catalyzed protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is described. Catalyzed by a Fe(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O2, α- and β-substituted styrenes were cleaved to afford benzaldehydes and aromatic ketones generally in high yields with excellent chemoselectivity and very good functional group tolerance, including those containing radical-sensitive groups. With α-halo-substituted styrenes, the oxidation took place with concomitant halide migration to afford α-halo acetophenones. Various observations have been made, pointing to a mechanism in which both molecular oxygen and the olefinic substrate coordinate to the iron center, leading to the formation of a dioxetane intermediate, which collapses to give the carbonyl product.

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Section: Results and Discussionmentioning

confidence: 99%

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂

2015

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Efficient Catalytic Corey–Chaykovsky Reactions Involving Ketone Substrates

2010

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It has been demonstrated for the first time that a sulfide catalyst, utilised at 20 mol% loading, can promote methylene transfer to ketones in the presence of methyl triflate and an organic base. This metal-free methodology is of broad scope -both aliphatic and aromatic ketones (including trifluoromethyl ketones) can be converted to synthetically useful terminal epoxides in excellent yields at room temperature.Keywords: Corey-Chaykovsky reaction; epoxides; methylene transfer; organocatalysis; sulfides Epoxides are among the most valuable synthetic building blocks available to an organic chemist. Hence, the synthesis of these spring-loaded electrophiles in enantiomerically pure form is of great interest.[1] Although there are many distinguished protocols for the synthesis of optically active substituted/ functionalised epoxides, [2] there is a dearth of methods for the catalytic synthesis of the corresponding unfunctionalised terminal epoxides.The Corey-Chaykovsky (CC) reaction [3] is a timehonoured and efficient methodology for the synthesis of these compounds. Initially this reaction involved the use of stoichiometric loadings of preformed sulf(ox)onium salts (in the presence of base) as the alkyl-transfer agent, which is naturally undesirable from an atom-economy perspective.In a landmark series of studies, Furukawa, [4a] Aggarwal [4b-d,g-i,l,n] and others [4e,f,j,k,m] demonstrated that the (asymmetric) addition of semi-stabilised ylides to carbonyl compounds is possible using catalytic sulfide loadings. However, the corresponding asymmetric methylene transfer (i.e., via a chiral non-stabilised ylide) has been characterised by moderate yields/ enantioselectivities and a requirement for (super)stoichiometric sulfide loadings.[5] For instance, Aggarwals [5d] and Goodmans [5e] benchmark literature protocols for the asymmetric sulfonium ylide mediated methylene transfer to benzaldehyde (1) involve the use of 100-200 mol% of chiral sulfides 3-4 and produce 2 in ca. 50-60% yield and up to 57% ee (Scheme 1, A). It is also noteworthy that these protocols involved the use of a modified version of the classical CC reaction involving a metal-mediated Simmons-Smith type carbenoid transfer. [5e,6] We recently reported an operationally simple catalytic procedure for metal-free methylene transfer to Scheme 1. Protocols for chiral sulfide mediated terminal epoxidation.

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Studies on the Autoxidation of Aryl Alkenes

Suprun

Opeida

2006

Chem. Eng. Technol.

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Autoxidation activity of substituted styrenes (aryl alkenes) and their product formation were studied in the temperature range of 65-125°C using cumene or chlorobenzene as solvent. It was observed that higher reaction temperatures, inert solvent, electron donating substituents, and bulky sterical groups at a-, orthoand para-positions promoted radical formation of epoxides and led to C=C oxidative cleavage. In contrast, electron accepting substituents and using cumene as the solvent favored the formation of oligomeric peroxides. The relative activity of all investigated styrenes could be correlated to the linear free energy (LFE) relation and the ionization potential. For a-substituted styrenes and ring substituted a-methylstyrenes LFE correlation for the reactivity of aryl alkenes and formation of epoxides was found to depend on the polar and steric factors. A general pathway for product formation by autoxidation of aryl alkenes has been proposed.

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Reaktivität und Selektivität bei der Oxidation von Styrolderivaten. V. Untersuchungen zur Oxidation vonα-substituierten Styrolen

Cited by 8 publications

References 37 publications

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂

Efficient Catalytic Corey–Chaykovsky Reactions Involving Ketone Substrates

Studies on the Autoxidation of Aryl Alkenes

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Reaktivität und Selektivität bei der Oxidation von Styrolderivaten. V. Untersuchungen zur Oxidation vonα-substituierten Styrolen

Cited by 8 publications

References 37 publications

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O2

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O2

Efficient Catalytic Corey–Chaykovsky Reactions Involving Ketone Substrates

Studies on the Autoxidation of Aryl Alkenes

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Product

Resources

About

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O₂