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Updated: Jun 23, 2026
Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes
Published on: September 12, 2018
Iron-Catalyzed Chemodivergent Sequential Reactions of Alkynes and Organozinc Reagents
Tao Cai1,2, Peng He1, Shen-Ao Xie1
1Academy for Advanced Interdisciplinary Studies, Frontiers Science Center of New Organic Matters, State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, College of Outstanding Engineers, Nankai University, Tianjin 300071, China.
Abstract:
Although enzymes easily achieve significant changes in reactivity through mutating only a single or a few residues reminiscent of "butterfly effect", achieving selectivity modulation in chemical catalysis requires major structural modifications or even entirely different catalysts. In this study, we found that in the iron-catalyzed unprecedented three-component reaction of alkynes with organozinc reagents, simply replacing a methyl group outside the catalytic pocket with a hydrogen atom (a mere 6% change in molecular weight) completely changed the chemoselectivity from dimerization/hydrozincation to dimerization/carbozincation, affording two types of conjugated dienylzinc reagents that are difficult to access by other means. This rarely observed "butterfly effect" in chemical catalysis is mainly attributed to the closely spaced potential energy surfaces of different spin states in the iron catalyst, which amplify subtle energy perturbations caused by substituent variation, ultimately leading to the reversal of chemoselectivity.
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02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
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02:35Electrophilic Addition to Alkynes: Hydrohalogenation
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
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02:34Preparation of Alkynes: Dehydrohalogenation
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02:38Electrophilic 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.