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Updated: Apr 17, 2026

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
Published on: February 16, 2020
A practical Lewis base catalyzed electrophilic chlorination of arenes and heterocycles
Sean M Maddox1, Christopher J Nalbandian, Davis E Smith
1Department of Chemistry and Biochemistry, San Diego State University , 5500 Campanile Drive, San Diego, California 92182-1030, United States.
Abstract:
A mild phosphine sulfide catalyzed electrophilic halogenation of arenes and heterocycles that utilizes inexpensive and readily available N-halosuccinimides is disclosed. This methodology is shown to efficiently chlorinate diverse aromatics, including simple arenes such as anthracene, and heterocycles such as indoles, pyrrolopyrimidines, and imidazoles. Arenes with Lewis acidic moieties also proved amenable, underscoring the mild nature of this chemistry. Lewis base catalysis was also found to improve several diverse aromatic brominations and iodinations.
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Halogenation of Alkenes
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Electrophilic Addition to Alkynes: Halogenation
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.

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