-Aminopyridinium salts generate nitrogen-centered radicals by means of photoredox catalysis. Herein, we report that they can be trapped by enol equivalents to give α-amino carbonyl compounds in excellent yields. The broad synthetic utility of this method is demonstrated by functionalization of ketones, aldehydes, esters enol equivalents, vinyl ethers, and 1,3-diketones without the need for prior conversion to enol derivatives. The developed method is easily scalable, offers broad substrate scope, high chemoselectivity.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1021/acs.joc.9b02073 | DOI Listing |
J Org Chem
January 2025
Henan Key Laboratory of Nanocomposites and Applications; Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou 450006, China.
A photoredox-catalyzed aminolactonization of unsaturated carboxylic acids was achieved using -aminopyridinium salts as the amino radical precursor. The transformation features mild conditions and a remarkably broad substrate scope, offering an efficient approach to construct a wide range of 4-sulfonamino 3,4-dihydroisocoumarins. Mechanistic studies indicate that the reaction proceeds via a distinctive -aminopyridinium salt-promoted electrophilic amination of 2-styrylbenzoic acids.
View Article and Find Full Text PDFOrg Lett
November 2024
Department of Chemistry, Indian Institute of Technology Indore, Indore 453552, Madhya Pradesh, India.
We report an organophotoredox-catalyzed silylation/germylation cascade cyclization of -alkenyl α-CF acrylamides under mild conditions. -Aminopyridinium salts act as hydrogen atom transfer reagents under photoredox catalysis in the generation of silyl and germyl radicals. An array of silyl- and germyl-substituted 3-CF-4-pyrrolin-2-one derivatives were constructed in a shorter reaction time with low catalyst loading in good to excellent yields at room temperature.
View Article and Find Full Text PDFOrg Lett
October 2024
State Key Lab of Urban Water Resource and Environment, School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China.
A N-heterocyclic carbene-catalyzed (NHC) three-component reaction involving -aminopyridinium salts, alkenes, and aldehydes for the synthesis of β-amino ketones is described. In this reaction, -aminopyridinium salts and the Breslow intermediate, which is generated from NHC and aldehydes, are utilized to undergo a single-electron transfer process, forming a ketyl radical intermediate and amidyl radicals. Subsequent to the formation of the amidyl radical, it undergoes selective capture by alkenes, followed by radical cross-coupling to yield the desired β-amino ketones.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
November 2024
Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, Republic of Korea.
Given the prevalence of pyridine motifs in FDA-approved drugs, selective fluoroalkylation of pyridines and quinolines is essential for preparing diverse bioisosteres. However, challenges are often faced with conventional Minisci reactions in achieving precise regioselectivity owing to competing reaction sites of pyridine and the limited availability of fluoroalkyl radical sources. Herein, we present a light-driven, C4-selective fluoroalkylation of azines utilizing N-aminopyridinium salts and readily available sulfinates.
View Article and Find Full Text PDFOrg Lett
June 2024
Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.
-centered nucleophilicity increases upon alkylation, and thus selective partial alkylation of ammonia and primary amines can be challenging: Poor selectivity and overalkylation are often observed. Here we introduce -aminopyridinium salts as ammonia surrogates for the synthesis of secondary amines via self-limiting alkylation chemistry. Readily available -aryl--aminopyridinium salts engage in -alkylation and depyridylation to afford secondary aryl-alkyl amines without any overalkylation products.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!