C−O coupling of Malonyl Peroxides with Enol Ethers via [5+2] Cycloaddition: Non‐Rubottom Oxidation

Abstract

Malonyl peroxides act both as oxidants and reagents for C−O coupling in reactions with methyl and silyl enol ethers. In the proposed conditions, the oxidative C−O coupling of malonyl peroxides with enol ethers selectively proceeds, bypassing the traditional Rubottom hydroxylation of enol ethers by peroxides. It was observed that the oxidative [5+2] cycloaddition of malonyl peroxides and enol ethers is the key stage of the discovered process. Oxidative C−O coupling of silyl enol ethers leads to the formation of α‐acyloxyketones with a free carboxylic acid group. A specially developed preparative one‐pot procedure transforms ketones via silyl enol ethers formation and the following coupling into α‐acyloxyketones with yields 35–88%. The acid‐catalyzed coupling with methyl enol ethers gives remarkable products while retaining the easily oxidizable enol fragment. Furthermore, these molecules contain a free carboxylic acid group, thus these nontrivial products contain two usually incompatible acid and enol ether groups.

Activation of O-Electrophiles via Structural and Solvent Effects: SN2@O Reaction of Cyclic Diacyl Peroxides with Enol Acetates

“…Now let us consider the final stage of the reaction, which is the elimination of the acetyl group originating from 1b. Based on experimental and computational results for the enol ethers, 36 the intermediate IM1 can be expected to rearrange into mixed anhydride IM3, which converts into the final product 3b via the elimination of the acetyl group (Scheme 5). To check if this route is energetically feasible, we located a TS of IM2 → 3b transformation.…”

“…Initially, the reaction of enol acetate 1a with cyclic diacyl peroxide 2 was tested in CH 2 Cl 2 and tetrahydrofuran (THF) at 20–25 °C for 24 h (Table , entries 1 and 2). These solvents worked well in our previous studies, but no conversion of 1a was observed in this case. The addition of p -TsOH·H 2 O (entry 3) led to a low (28%) yield of 3a .…”

Synthetic Access to α-Oxoketene Aminals by the Nucleophilic Addition of Enol Silane-Derived Palladium(II) Enolates to Carbodiimides

“…Trimethyl((1-phenylvinyl)oxy)silane (2a), 69 trimethyl((1-(ptolyl)vinyl)oxy)silane (2b), 69 ((1-(4-methoxyphenyl)vinyl)oxy)trimethylsilane (2c), 69 ((1-(benzo[d] [1,3]dioxol-5-yl)vinyl)oxy)trimethylsilane (2d), 69 ((1-(3-methoxyphenyl)vinyl)oxy)trimethylsilane (2e), 70 trimethyl((1-(4-(trifluoromethyl)phenyl)v i n y l ) o x y ) s i l a n e ( 2 f ) , 7 1 m e t h y l 3 -( 1 -((trimethylsilyl)oxy)vinyl)benzoate (2g), 72 4-(1-((trimethylsilyl)-oxy)vinyl)benzonitrile (2h), 71 trimethyl((1-(4-nitrophenyl)vinyl)oxy)silane (2i), 69 ((1-(4-fluorophenyl)vinyl)oxy)trimethylsilane (2j), 69 ((1-(4-chlorophenyl)vinyl)oxy)trimethylsilane (2k), 69 ((1-(4-bromophenyl)vinyl)oxy)trimethylsilane (2l), 69 ((1-(4iodophenyl)vinyl)oxy)trimethylsilane (2m), 69 ((1-(2-chlorophenyl)vinyl)oxy)trimethylsilane (2n), 73 trimethyl((1-(naphthalen-1-yl)vinyl)oxy)silane (2o), 69 trimethyl((4-phenylbuta-1,3-dien-2-yl)oxy)silane (2p), 74 trimethyl((4-(p-tolyl)buta-1,3-dien-2-yl)oxy)silane (2q), 74 trimethyl((1-(1-methylcyclopropyl)vinyl)oxy)silane (2r), 75 ((3,3-dimethylbut-1-en-2-yl)oxy)trimethylsilane (2s), 76 (cyclopent-1-en-1-yloxy)trimethylsilane (2t), 7 7 and ethyl 2-oxo-3-((trimethylsilyl)oxy)but-3-enoate (2u). 78 The following carbodiimides were prepared as per the literature protocols.…”

The Ligand Free Palladium(II)-Catalyzed Regioselective 1,2-Addition of Enol Silanes to Quinones to Access 4-Hydroxy-4-(2-oxo-2-arylethyl)cyclohexadien-1-ones and Synthetic Applications

“…58 ((1-(2-Chlorophenyl)vinyl)oxy)trimethylsilane (2n). 62 Trimethyl((1-(naphthalen-1-yl)vinyl)oxy)silane (2o). 58 Trimethyl((4-phenylbuta-1,3-dien-2-yl)oxy)silane (2p).…”