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Updated: May 10, 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
A highly chemoselective and practical alkynylation of thiols
1Laboratory of Catalysis and Organic Synthesis, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCSO, BCH 4306, 1015 Lausanne, Switzerland.
Abstract:
A thiol-alkynylation procedure utilizing the hypervalent iodine alkyne transfer reagent TIPS-ethynyl-benziodoxolone has been developed. This scalable reaction proceeds in five minutes at room temperature in an open flask using commercially available reagents. The scope of the reaction is broad, with a variety of phenolic, benzylic, heterocyclic, and aliphatic thiols undergoing alkynylation in excellent yield. The method is highly chemoselective as a vast array of functional groups are tolerated. The utility of the thiol-alkynylation in postsynthetic elaboration has been demonstrated through the facile installment of a fluorophore tag on a cysteine-containing peptide.
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02:33Preparation and Reactions of Thiols
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Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
02:34Preparation of Alkynes: Dehydrohalogenation
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
02:26Preparation and Reactions of Sulfides
01:38Preparation of Alcohols via Substitution Reactions
Alcohols can be synthesized from alkyl halides via nucleophilic substitution reactions. The highly polar carbon-halogen bond in the substrate makes halide a good leaving group. The hydroxide ion or water can act as a nucleophile to take the place of halide and form an alcohol. The substitution reactions occur via two different reaction pathways, SN1 or SN2, depending on the nature of carbon attached to the halide.
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