A practical free-radical approach to 1,4-dicarbonyl compounds

Peralta‐Hernandez, Eduardo; Blé-González, Ever A.; Gracia-Medrano-Bravo, Víctor Alfonso; Cordero‐Vargas, Alejandro

doi:10.1016/j.tet.2015.02.077

Cited by 15 publications

(14 citation statements)

References 38 publications

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“…Another promising methodology involves the alkyl radical addition to a reactive C−C double bond (Figure 1 c). This methodology uses enol ethers and their derivatives, including silyl enol ethers, [7] stannyl enolates, [8] enamines, [9, 10] acetates, [11] and vinyl ethers, [12] as C−C double‐bond sources. Despite the importance of substituted 1,4‐dicarbonyl compounds, the direct tertiary alkylation of a ketone has not yet been established because it is difficult to control the reactivity of a tertiary alkyl radical (α‐radical) due to steric hindrance; it also requires pre‐formed highly reactive enolates or their derivatives.…”

Section: Figurementioning

confidence: 99%

Direct α‐Tertiary Alkylations of Ketones in a Combined Copper–Organocatalyst System

et al. 2021

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Herein, we report an efficient method for the tertiary alkylation of a ketone by using an α‐bromocarbonyl compound as the tertiary alkyl source in a combined Cu‐organocatalyst system. This dual catalyst system enables the addition of a tertiary alkyl radical to an enamine. Mechanistic studies revealed that the catalytically generated enamine is a key intermediate in the catalytic cycle. The developed method can be used to synthesize substituted 1,4‐dicarbonyl compounds containing quaternary carbons bearing various alkyl chains.

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Section: Figurementioning

confidence: 99%

Direct α‐Tertiary Alkylations of Ketones in a Combined Copper–Organocatalyst System

et al. 2021

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“…from iodoacetic acid and allylic alcohol 8, which would be prepared by a PGF route from (R)-citronellal (7). The advanced intermediate 11 for the synthesis of γ-lycorane (2) can be prepared from a radical-ionic sequence 5 between enol acetate 10 and iodoacetonitrile. The former compound would be obtained in three steps from cyclohexene oxide (9) in a PGF fashion.…”

Section: Syn Thesismentioning

confidence: 99%

“…For instance, either the transferred atom or group (halogen, usually) provides a new starting point for additional radical or ionic reactions. Accordingly, in recent years, our group has developed new radical-ionic sequences for the preparation of epoxides, 3 lactams, 4 1,4-dicarbonyl compounds, 5 and iodolactones, 6 showcasing the usefulness of this strategy (Scheme 1). Now, by using these synthetic strategies, the total synthesis of (-)-boschnialactone (1) and (±)-γ-lycorane (2) is reported.…”

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confidence: 99%

A Free-Radical and Protecting-Group-Free Approach to (–)-Boschnialactone and γ-Lycorane

Basante-Avendaño¹,

Guerra-Ayala²,

Sánchez-Eleuterio³

et al. 2019

Synthesis

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The protecting-group-free (PGF) and free-radical-based synthesis of two structurally different natural products, (–)-boschnialactone and γ-lycorane, is reported. The key step in both syntheses is a radical–ionic sequence for construction of the principal structure (a six-membered lactone and a 1,4-dicarbonyl compound, respectively), allowing short and rapid access to these natural products through a PGF route.

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“…In the case of enol acetates, the trifluoromethyl and azide radicals are intercepted by the olefin, generating the benzylic radical 14 which is likely oxidized to the corresponding cation 15 . Subsequent loss of acetyl cation will result in the product(s) . Although Scheme depicts a free azide radical, it is possible that a Mn III species may be associated with the azide moiety .…”

Section: Evaluation Of Reaction Conditions For Mno2‐catalyzed Oxidatimentioning

confidence: 99%

Manganese‐Dioxide‐Catalyzed Trifluoromethylation and Azidation of Styrenyl Olefins via Radical Intermediates

2017

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Am anganese-dioxide-catalyzed trifluoromethylation of styrenes and enol acetates using the Langlois reagent is reported. Employing oxygen/air as the oxidant, styrenes afforded am ixture of the trifluoromethylacohol and ketone products in good overall yields. The protocol also works successfully for converting a-methylstyrened erivatives to the corresponding trifluoromethyl alcohols. The keto-trifluoromethylated products could be obtained exclusively when using enol acetates as substrates under the same reaction conditions. The method was extended to the radical azidationo fe nol acetates using trimethylsilyl azide to furnish the corresponding azido-ketones in good yields.Catalytic strategies for olefin functionalization form av ersatile repertoire of reactions using whichadiversea rray of functionalities can be generated. [1] The applicationo ff irst row transition metal catalysts forf unctionalization of olefins via free radical pathways has been an attractive synthetic pathway to explore, as demonstrated by recently reported elegant studies. [2] Amongt he many challenges, the controlo fo xidation state outcome, application of minimally functionalized olefins, and the development of inexpensive catalyst systems remaina tt he forefront. In this context,t he trifluoromethylation of olefins has been studied extensively with many catalysts including Cu, [3] Fe, [4] Pd, [5] Ag, [6] Ru, [7] and photoredox systems. [8] Oxidative trifluoromethylations employing as ilver catalystw ith various oxidants have also been reported. [9] Given the rich chemistry of manganese in Nature as well as in synthetic systems, [10] we were interestedi nd eveloping radicalt rifluoromethylation [11] and azidation [2k, 12] of olefins using readily available reagents and inexpensivec atalyst [2a, j, k, 13] which could operate in conditions that didn ot involve stoichiometrica mountso fa dditives [2a, b] and oxidants such as peroxides. [2c, 14] We selected vinyl naphthalene for optimizations tudy and performed variouse xperiments to ascertain the best condi- [a] Scheme1.Oxytrifluoromethylation reaction scope.Reactionconditions: styrenederivative (1 equiv.), CF 3 SO 2 Na (2 equiv.), MnO 2 (0.2 equiv.), and K 2 S 2 O 8 (0.2 equiv.) werec ombined in DMF (2 mL) and stirreda tr tf or 6-24 hours.Scheme2.Reactionscope: a-methylstyrenes. Isolated yields are reported.[a] Reaction performed under air.

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A practical free-radical approach to 1,4-dicarbonyl compounds

Cited by 15 publications

References 38 publications

Direct α‐Tertiary Alkylations of Ketones in a Combined Copper–Organocatalyst System

Direct α‐Tertiary Alkylations of Ketones in a Combined Copper–Organocatalyst System

A Free-Radical and Protecting-Group-Free Approach to (–)-Boschnialactone and γ-Lycorane

Manganese‐Dioxide‐Catalyzed Trifluoromethylation and Azidation of Styrenyl Olefins via Radical Intermediates

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