Oxidation Of Silyl Enol Ethers Research Articles

Electrochemical α-Arylation of Ketones via Anodic Oxidation of In Situ Generated Silyl Enol Ethers.

An electrochemical procedure for the α-arylation of ketones has been developed. The method is based on the generation and one-pot anodic oxidation of silyl enol ethers in the presence of the arene. This strategy avoids isolation of the silyl enol intermediate and the utilization of external supporting electrolytes. Intermolecular arylations, which had not been reported so far, are possible when electron-rich arenes are utilized as coupling partners. The method has been demonstrated for a wide variety of aryl ketones and activated arenes, with moderate to good yields (up to 69%) obtained. Mechanistic insights and a theoretical rationale that explains the ketone α-arylation versus dimerization selectivity are also presented.

ChemInform Abstract: Synthesis of Silyl Monoperoxyketals by Regioselective Cobalt‐Catalyzed Peroxidation of Silyl Enol Ethers: Application to the Synthesis of 1,2‐Dioxolanes.

AbstractOptimized conditions for the oxidation of silyl enol ethers with molecular oxygen and triethylsilane are presented.

ChemInform Abstract: Catalytic Oxidation of Silyl Enol Ethers to 1,2‐Diketones Employing Nitroxyl Radicals.

AbstractA novel method allows the synthesis of 1,2‐diketones under mild conditions through nitroxyl‐radical catalyzed oxidation of silyl enol ethers with magnesium monoperoxyphthalate as the oxidant.

Catalytic Oxidation of Silyl Enol Ethers to 1,2-Diketones Employing Nitroxyl Radicals

A novel and efficient method for the preparation of 1,2-diketones is reported. A series of α-diketones were readily prepared by the nitroxyl-radical-catalyzed oxidation of silyl enol ethers using magnesium monoperoxyphthalate hexahydrate (MMPP⋅6H₂O) as the co-oxidant.

Metal Nitrite: A Powerful Oxidizing Reagent

An efficient and simple source of nitroso reagents and their oxidation reactions are described. The combination of a Lewis acid and a metal nitrite was applied to the oxidation of silyl enol ethers. Amino acid and peptide derivatives were easily accessed through in situ C-C bond cleavage of fully substituted silyl enol ethers upon oxidation.

A density functional theory study on π-nucleophilicity and electron-transfer oxidation of silyl enol ethers and ketene silyl acetals

Conceptual density functional theory based reactivity descriptors are used to study nucleophilic reactivity of silyl enol ethers and ketene silyl acetals having substituents of both electron releasing and electron withdrawing nature at various key positions of the molecules. While intramolecular reactivity towards electrophilic attack is studied on the basis of local softness ( s k - ) and local nucleophilicity index ( N k ), intermolecular reactivity is assessed using group softness ( s g - ) and group nucleophilicity ( N g ). Ionization potential, inner sphere reorganization energy and structural changes associated with single electron-transfer oxidation for the selected trimethylsilyl enolates have been evaluated. Role of β-methyl substituents are found to be crucial for both nucleophilic reactivity and single electron-transfer oxidation of these systems.

Triphenylcarbenium Tetrafluoroborate

Triphenylcarbenium tetrafluoroborate, also called trityl fluoroborate, is widely applied in organic reactions, [¹] such as dehydrogenation, [²] deprotection of ketone acetals, [³] alkyl ethers, [4] oxidation of silyl enol ethers, [5] preparation of cationic organometallics [6] or organic complexes, [7] as a polymerization catalyst [8] and as a Lewis acid catalyst. [9] Trityl fluoroborate is a yellow solid (mp 200 ˚C dec.), which is soluble in most organic solvents, e.g., dichloromethane, tetrahydrofuran, and reacts with nucleophilic solvents, e.g., water. Several preparation methods were described in the literature as early as the 1940s. Dauben et al. used triphenylcarbinol and 48% fluoroboric acid, while removing water from the reaction mixture by adding acetic anhydride. [¹0a] In 1972, Olah et al. developed a more convenient and economical route using trityl chloride and anhydrous tetrafluoroboric acid dimethyl etherate in dry benzene. [¹0b]

Pd(OH)2/C‐Mediated Selective Oxidation of Silyl Enol Ethers by tert‐Butylhydroperoxide, a Useful Method for the Conversion of Ketones to α,β‐Enones or β‐Silyloxy‐α,β‐enones.

Pd(OH)2-catalyzed oxidation of silyl enol ethers by t-BuOOH gives either β-silyloxy-α,β-enones or α,β-enones in good yields depending on the base used.

Pd(OH)2/C-Mediated Selective Oxidation of Silyl Enol Ethers by tert-Butylhydroperoxide, a Useful Method for the Conversion of Ketones to α,β-Enones or β-Silyloxy-α,β-enones

[reaction: see text] Pd(OH)2-catalyzed oxidation of silyl enol ethers by t-BuOOH gives either beta-silyloxy-alpha,beta-enones or alpha,beta-enones in good yields depending on the base used.

Asymmetric oxidation of silyl enol ethers using chiral dioxiranes derived from α-fluoro cyclohexanones

Asymmetric oxidation of silyl enolethers derived from tetralone, 2-methyl-tetralone, propiophenone and deoxybenzoin using chiral dioxiranes generated in situ from oxone and new chiral α-fluorinated cyclohexanones or fructose-derived ketone have been studied. It was observed that tetrasubstituted silyl enolethers are poor substrates, that substitution at C8 of the fluoro-ketones has a significant effect on the enantioselectivities obtained and that the fructose-derived-ketone provides higher enantioselectivities. The absolute configuration of the major hydroxy ketones obtained can be rationalized using a spiro model proposed for epoxidation of olefins.

Palladium‐Catalyzed or ‐Promoted Oxidation via 1,2‐ or 1,4‐Elimination: Oxidation of Silyl Enol Ethers and Related Enol Derivatives to α,β‐Unsaturated Enones and Other Carbonyl Compounds

AbstractFor Abstract see ChemInform Abstract in Full Text.

ChemInform Abstract: Oxidation of Silyl Enol Ethers by Using IBX and IBX×N‐Oxide Complexes: A Mild and Selective Reaction for the Synthesis of Enones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Oxidation of silyl enol ethers by using IBX and IBX.N-oxide complexes: a mild and selective reaction for the synthesis of enones.

α,β-Unsaturated carbonyl compounds can be prepared by the oxidation of trimethylsilyl enol ethers with IBX (1) or IBX⋅MPO (2). A diverse set of carbonyl compounds can be dehydrogenated with ease by using this method. Trimethylsilyl enol ethers such as 4, which are formed in situ by the addition of an organometallic species to an enone, can be dehydrogenated with 1 or 2 to give a functionalized enone (e.g. 3→5). IBX = iodoxybenzoic acid; MPO = 4-methoxypyridine-N-oxide.

Oxidation of Silyl Enol Ethers by Using IBX and IBX⋅N-Oxide Complexes: A Mild and Selective Reaction for the Synthesis of Enones

Oxidation of Silyl Enol Ethers by Using IBX and IBX⋅N-Oxide Complexes: A Mild and Selective Reaction for the Synthesis of Enones

A novel palladium-catalyzed intramolecular redox reaction.

[reaction: see text] A new type of palladium-catalyzed redox reaction is described, forming enones from 2-(2-bromobenzyl)-ketones with an overall loss of HBr. The scope and limitations of the reaction are demonstrated by a series of cyclic and acyclic substrates. The mechanism most probably involves the formation of an intramolecular arylpalladium enolate and is related to the oxidation of silyl enol ethers with palladium acetate.

ChemInform Abstract: Facile Oxidation of Silyl Enol Ethers with Hydrogen Peroxide Catalyzed by Methyltrioxorhenium.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Synthesis of Optically Active α‐Hydroxy Ketones by Enantioselective Oxidation of Silyl Enol Ethers with a Fructose‐Derived Dioxirane.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Synthesis of Optically Active α‐Hydroxy Carbonyl Compounds by the Catalytic, Enantioselective Oxidation of Silyl Enol Ethers and Ketene Acetals with (Salen)manganese(III) Complexes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Facile Oxidation of Silyl Enol Ethers with Hydrogen Peroxide Catalyzed by Methyltrioxorhenium

Facile Oxidation of Silyl Enol Ethers with Hydrogen Peroxide Catalyzed by Methyltrioxorhenium

Synthesis of optically active α-hydroxy ketones by enantioselective oxidation of silyl enol ethers with a fructose-derived dioxirane

Optically active α-hydroxy ketones 3 have been prepared in moderate to high enantioselectivities by the asymmetric oxidation of the silyl enol ethers 2 with in situ generated dioxirane from the fructose-derived ketone 1. Best results (ee values up to 82%) for this novel non-transition metal mediated asymmetric α-hydroxylation may be obtained, when an excess of the fructose-derived ketone 1 is employed at pH ca. 8 and short reaction times. Valuable mechanistic information on the spiro versus planar transition states for the oxygen-transfer process has been aquired through the absolute configuration of the resulting α-hydroxy ketone 3 products.