Efficient regioselective aldol condensation of methyl ketones promoted by organoaluminum compounds, and its application to muscone synthesis

“…17 Recombination between A and the phenyltelluryl radical provides 6. 18 Hence, this experiment clarified the important role of the UV LED in starting the radical process.…”

Section: ■ Results and Discussionmentioning

confidence: 67%

Et₃Al/Light-Promoted Radical-Polar Crossover Reactions of α-Alkoxyacyl Tellurides

Yamada,

Yoshinaga,

Matsui

et al. 2024

J. Org. Chem.

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Here, we report new radical-polar crossover reactions of α-alkoxy carbon radicals for constructing highly oxygenated molecules with contiguous stereocenters. The method employs a 370 nm UV light-emitting diode (LED) for the photoexcitation of α-alkoxyacyl telluride, and Et 3 Al as the radical initiator and terminator. First, Et 3 Al and UV LED promoted radical coupling between the α-alkoxyacyl telluride and cyclopentenone via C−Te bond homolysis, CO expulsion, and C−C bond formation. Second, Et 3 Al converted the radical species to the corresponding aluminum enolate. Third, the second C−C bond formation occurred via a polar mechanism: intermolecularly with aldehydes/ketones and intramolecularly with epoxide, producing aldol and S N 2 adducts, respectively. The present coupling reactions increase the molecular complexity in a single step by stereoselective formation of the two hindered C−C bonds. The devised method is expected to be useful for the expeditious assembly of densely oxygenated natural products.

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“…The method in hand represents a valuable addition to kinetically controlled regioselectivities as they were observed in several other direct aldol additions to unsymmetrical methyl ketones. − For control of regioselectivity in aldol additions of trimethylsilyl enol ethers of unsymmetrical ketones depending on counteractions (lithium or potassium). see ref .…”

Section: Discussionmentioning

confidence: 99%

Tetranuclear BINOL−Titanium Complex in Selective Direct Aldol Additions

et al. 2008

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The extremely robust and water-stable tetranuclear complex Ti(4)(micro-BINOLato)(6)(micro(3)-OH)(4) (1) catalyzes the direct aldol addition with high degrees of regioselectivity at the sterically more encumbered alpha-side of unsymmetrical ketones. The formation of quaternary stereocenters is described. Oxygen-containing ene components can also be used as starting material in these reactions. When used with aliphatic aldehydes, acetals 18 or acetals of aldol adducts 20 were observed. As few as 0.2 mol % loadings with this catalyst 1 were enough to complete the reactions. Mechanistical aspects of the reactions are discussed.

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Efficient regioselective aldol condensation of methyl ketones promoted by organoaluminum compounds, and its application to muscone synthesis

Cited by 27 publications

References 6 publications

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Et₃Al/Light-Promoted Radical-Polar Crossover Reactions of α-Alkoxyacyl Tellurides

Tetranuclear BINOL−Titanium Complex in Selective Direct Aldol Additions

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Efficient regioselective aldol condensation of methyl ketones promoted by organoaluminum compounds, and its application to muscone synthesis

Cited by 27 publications

References 6 publications

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Et3Al/Light-Promoted Radical-Polar Crossover Reactions of α-Alkoxyacyl Tellurides

Tetranuclear BINOL−Titanium Complex in Selective Direct Aldol Additions

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Product

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Et₃Al/Light-Promoted Radical-Polar Crossover Reactions of α-Alkoxyacyl Tellurides