Synthesis of α-Keto Amides by a Pyrrolidine/TEMPO-Mediated Oxidation of α-Keto Amines

An efficient base, additive and metal-free synthetic methods for α-ketothioamide and α-ketoamide derivatives from readily available sulfoxonium ylides have been described. Sulfoxonium ylides with primary or secondary amines afforded α-ketothioamides in the presence of elemental sulfur, whereas α-ketoamides were produced when I 2 and TBHP were present. The reaction proceeded well at room temperature and generated the corresponding molecules in good to excellent yields. The reaction can be scaled-up and tolerated by a range of functional groups with simple operational procedures.

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Aminoxyl-Catalyzed Electrochemical Diazidation of Alkenes Mediated by a Metastable Charge-Transfer Complex

Siu

2019

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We report the development of a new aminoxyl radical catalyst, CHAMPO, for the electrochemical diazidation of alkenes. Mediated by an anodically generated charge-transfer complex in the form of CHAMPO−N 3 , radical diazidation was achieved across a broad scope of alkenes without the need for a transition metal catalyst or a chemical oxidant. Mechanistic data support a dual catalytic role for the aminoxyl serving as both a single-electron oxidant and a radical group transfer agent. The discovery of reactions mediated by organic radicals continues to provide solutions to challenging synthetic problems in traditional two-electron chemistry. 1 In this context, design and implementation of new catalytic strategies have both expanded the toolbox available for accessing new synthetic targets and transformed the fundamental understanding of reactions involving open-shell pathways. 2 For example, persistent aminoxyl radicals [e.g., (2,2,6,6tetramethylpiperidin-1-yl)oxyl (TEMPO)] have been extensively explored in catalytic oxidation reactions with both conventional chemical 3 and electrochemical techniques, 4 which has given rise to synthetically useful processes for small-molecule and polymer syntheses. Despite significant advances, we contend that the scope of TEMPO chemistry remains to be fully explored. TEMPO and related N-oxyl radicals can undergo one-electron redox processes, granting access to three discrete oxidation states. 4 This feature distinguishes these radicals from common organic compounds and likens them to many transition metal complexes. In this fashion, TEMPO has been shown to enable single-electron oxidation events in an inner-sphere manner via the formation of metastable closed-shell intermediates. 5,6 Nevertheless, the systematic use of the "metallic" character of N-oxyls in catalyst development remains meager. 7 To date, reactions catalyzed by N-oxyls are largely confined to oxidations of alcohols, 8 aldehydes, 9 amines, 10 (thio)amides, 11 and peroxyl radicals. 12 In *

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Synthesis of α-Keto Amides by a Pyrrolidine/TEMPO-Mediated Oxidation of α-Keto Amines

Abstract: A mild procedure has been developed for the synthesis of α-keto amides by α-oxidation of the corresponding α-keto amines mediated by pyrrolidine and TEMPO. The method can also be applied to the synthesis of α-keto thioamides and α-keto amidines.

Cited by 3 publications

References 8 publications

Pyridine-Enabled C–N Bond Activation for the Rapid Construction of Amides and 4-Pyridylglyoxamides by Cooperative Palladium/Copper Catalysis

Pyridine-Enabled C–N Bond Activation for the Rapid Construction of Amides and 4-Pyridylglyoxamides by Cooperative Palladium/Copper Catalysis

Metal-Free Syntheses of α-Ketothioamide and α-Ketoamide Derivatives from Sulfoxonium Ylides

Aminoxyl-Catalyzed Electrochemical Diazidation of Alkenes Mediated by a Metastable Charge-Transfer Complex

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