Iodination of Substituted Alkynes in the Presence of Cadmium(II) Acetate

A convenient and selective method for the preparation of substituted iodoalkynes, iodoalkenes based on the interaction of propargylic compounds with iodine in the presence of readily available cadmium (II) acetate in some solvents was developed. The highest yields of iodoalkynes and iodoalkenes were recorded using DMSO as the solvent. An excess of the alkylpropargyl substrate unambiguously led to iodolkynes. By varying the reaction conditions using a twofold excess of iodine in DMSO, methanol or ethanol it was possible to achieve a one‐pot preparation of triiodoalkenes. The interaction of iodine with propargyl substrates could be represented in two ways: formation and further nucleophilic transformation of the iodonium complex under the influence of the acetate ion and generation of π‐coordinated species and elimination of acetic acid. We have established a practical approach for the mono‐, and triiodination of alkylpropargyl ethers, employing readily available cadmium (II) acetate as a reagent. The method is applicable to the efficient and chemoselective synthesis of various iodoalkynes and triiodoalkenes.