Access to Natural Valparanes and Daucanes: Enantioselective Synthesis of (−)-Valpara-2,15-diene and (+)-Isodaucene

Moral, José F. Quı́lez del; Pérez, Álvaro; Herrador, María del Mar; Barrero, Alejandro F.

doi:10.1021/acs.jnatprod.8b00129

Cited by 6 publications

(1 citation statement)

References 62 publications

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“…Investigations have naturally moved toward the pursuit of enantioselective processes. The ready availability of enantiopure epoxides from allylic alcohol using Sharpless’ oxidation strategy has opened routes to enantioselective syntheses of natural products. , However, the search for enantiopure ligands to perform regio- and enantioselective ring opening was the biggest challenge. The first developments arose from the desymmetrization of meso -epoxides .…”

Section: Chiral Transition-metal-catalyzed Asymmetric Radical Processesmentioning

confidence: 99%

Enantioselective Radical Reactions Using Chiral Catalysts

Mondal¹,

et al. 2022

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Scheme 24 Enantioselective Radical Hydroacylation of Enals with α-Ketoacids byMerging Photoredox Catalysis with Amine Catalysis.Jang et al. exploited enantioselective tandem Michael addition/oxyamination of α,β-unsaturated aldehydes by combining asymmetric iminium catalysis using organocatalyst with photoinduced SOMO catalysis using N719/TiO2. 60 Here, TiO2 acts as a second cooperative photocatalyst along with Ru photocatalyst N719 which bound to the latter, increases the enantio-and diastereoselectivity of the process. Adamantane carboxylic acid (30 mol%) was used as an additive which promotes formation of iminium ion 2.1.48A from aldehyde 2.1.48 and chiral amine catalyst. This iminium intermediate then reacts with diethyl malonate to provide intermediate 2.1.48B which either undergoes hydrolysis to form β-substituted aldehyde 2.1.50 or photo-oxidation by the photoexcited Ru(II) dye to form enamine radical 2.1.48C. Subsequent addition of TEMPO to radical intermediate 2.1.48BC followed by hydrolysis afforded the desired product 2.1.49 (Scheme 25). This mechanism is obeying to a polar/radical crossover sequence where the first stereocontrol arises from the addition of the malonate.Recently, Bach group reported promising preliminary results of enantioselective [2+2] photocycloaddition of cinnamaldehyde in the presence of ruthenium photocatalyst and proline derived organocatalyst. 61

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Section: Chiral Transition-metal-catalyzed Asymmetric Radical Processesmentioning

confidence: 99%

Enantioselective Radical Reactions Using Chiral Catalysts

Mondal¹,

et al. 2022

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Ring‐Opening Reactions of Epoxides With Titanium(III) Reagents

RajanBabu¹,

Nugent²,

Halder³

2022

Organic Reactions

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The ring‐opening reactions of epoxides with titanium(III) reagents such as Cp 2 TiCl are critically reviewed, including the scope, limitations, and mechanism of these synthetically useful transformations. The initial reaction proceeds by single‐electron transfer to give a carbon‐centered β‐titanoxy radical. The resulting radical can be terminated by a number of different reaction pathways, including epoxide deoxygenation, reduction to the alcohol, intermolecular addition to activated olefins, and intramolecular addition (cyclization). The literature is surveyed from the first reported examples in 1988 through October, 2021.

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