Superacid-Promoted Reactions of α-Ketoamides and Related Systems

Sai, Kiran Kumar Solingapuram; Esteves, Pierre M.; Penha, Eduardo Tanoue da; Klumpp, Douglas A.

doi:10.1021/jo801208m

Cited by 83 publications

(23 citation statements)

References 26 publications

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“…It was converted to azaspirocyclohexadieneone 3 am using catalytic Cu(OAc) 2 under oxygen atmosphere (Scheme b) . Furthermore, 3 a rearranges to provide 3,3‐disubstituted oxyindole 3 an in superacidic condition (Scheme c) . The alkynamide product 3 ag undergoes selenylative spirocyclization with diphenyldiselenide to form 3 ao in presence of blue LED under oxygen atmosphere (Scheme d) …”

Section: Resultsmentioning

confidence: 99%

Photoredox‐Catalyzed Tandem Demethylation of N,N‐Dimethyl Anilines Followed by Amidation with α‐Keto or Alkynyl Carboxylic Acids

et al. 2019

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We report herein, a biomimetic approach for highly selective monodemethylation of N,N-dimethyl anilines to generate secondary amines and subsequent coupling with α-ketocarboxylic acids or alkynyl carboxylic acids to form α-ketoamides or alkynamides respectively under visible light photoredox catalyst in a single operation. From the deuterium-labeling experiment, it was probed that demethylation is the slowest step in this tandem process. Whereas, control experiments and spectroscopic studies revealed that photoredox catalyst is also involved in the subsequent amidation step. The reaction proceeds smoothly at room temperature providing moderate to excellent yield of the coupling products. The amides have also been converted to a series of biologically active spiro compounds.

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Section: Resultsmentioning

confidence: 99%

Photoredox‐Catalyzed Tandem Demethylation of N,N‐Dimethyl Anilines Followed by Amidation with α‐Keto or Alkynyl Carboxylic Acids

et al. 2019

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“…Forschungsartikel activation of this intermediate, [44] must drive the stereoselective polycyclization process to 4v.Sterically-controlled by the presence of the methano bridge,o nly one diastereomer,f or which aconformation placing the Hgroup at the upper face of the bridged benzazocane (Cv' ' maj), cyclizes to generate product 4v after aromatization. Thei ntermediate Cv' ' min does not cyclize and the product resulting from its deprotonation after hydrolysis can be collected (see SI).…”

Section: Angewandte Chemiementioning

confidence: 99%

Enantioenriched Methylene‐Bridged Benzazocanes Synthesis by Organocatalytic and Superacid Activations

et al. 2019

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Achieving in a straightforward way the synthesis of enantioenriched elaborated three‐dimensional molecules related to bioactive natural products remains a long‐standing quest in organic synthesis. Enantioselective organocatalysis potentially offers a unique opportunity to solve this problem, especially when combined with complementary modes of activation. Here, we report the sequential association of organocatalytic and superacid activations of simple linear achiral readily available precursors to promote the formation of unique highly elaborated chiral methylene‐bridged benzazocanes exhibiting three to five fully‐controlled stereocenters. This peculiar backbone, difficult to assemble by standard synthetic approaches, is closely related to bioactive natural and synthetic morphinans and benzomorphans. The formation of a highly reactive chiral 7‐membered ring N‐acyl iminium superelectrophilic ion, evidenced by low‐temperature in situ NMR experiments, triggers a challenging stereoselective Friedel–Crafts‐type cyclization.

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“…[20] In addition to their therapeutic importance, α-keto amides also serve as starting substrates in several organic transformations, for example, intramolecular arylations and β-lactam formation. [21] The synthesis of α-keto amides has been achieved by various methods. The most common amongst these methods include oxidative amidation of terminal alkynes, [22] oxidation of α-methylene group of amide functionality, [23] and oxidative coupling of aldehydes and isocyanides.…”

Section: Introductionmentioning

confidence: 99%

Visible‐Light Mediated Photooxidative Synthesis of α‐Keto Amides

2019

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Photocatalytic amidation of α-keto aldehydes is herein investigated. This transformation was achieved using rose bengal as photocatalyst at room temperature under ambient air and under irradiation of a 20 W white LED bulb. The method is mild, efficient and environmentally benign. This photocatalytic method is compatible with different unsubstituted and substituted α-keto aldehydes having electron-withdrawing or -donating groups, secondary amines, cyclic or acyclic, and primary aliphatic amines. Mechanistic studies reveal that the reaction proceeds via oxidative quenching of the photocatalyst.

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Superacid-Promoted Reactions of α-Ketoamides and Related Systems

Cited by 83 publications

References 26 publications

Photoredox‐Catalyzed Tandem Demethylation of N,N‐Dimethyl Anilines Followed by Amidation with α‐Keto or Alkynyl Carboxylic Acids

Photoredox‐Catalyzed Tandem Demethylation of N,N‐Dimethyl Anilines Followed by Amidation with α‐Keto or Alkynyl Carboxylic Acids

Enantioenriched Methylene‐Bridged Benzazocanes Synthesis by Organocatalytic and Superacid Activations

Visible‐Light Mediated Photooxidative Synthesis of α‐Keto Amides

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