Recent Advances in Iodine-Mediated Radical Reactions.

Over the past two decades, iodine-mediated free radical reactions have been extensively explored and employed in chemical transformations that complement traditional ionic reactions. In this review, we have updated the progress of the iodine-mediated radical reactions in organic synthesis reported between 2015 and mid-2024, and organized the reactions according to their mechanistic pathways. In general, the proposed mechanisms can be divided into four categories based on the radical initiation or its preceding steps, namely, (1) formation of a covalent X-I (X=C, N, S, Se) bond, which subsequently participates in a radical reaction; (2) formation of a noncovalent N···I bond, which assists the homolysis of the I-I bond; (3) formation of the key iodine radicals by visible-light or heat induced homolysis of I or by electrochemical oxidation of iodide; (4) iodine induced peroxide decomposition single electron transfer (SET) mechanism to generate alkoxy or alkyl peroxy radicals.

-BuNI/KSO-MEDIATED C-N COUPLING BETWEEN ALDEHYDES AND AMIDES.

-BuNI/KSO mediated C-N coupling between aldehydes and amides is reported. A strong electronic effect is observed on the aromatic aldehyde substrates. The transformylation from aldehyde to amide takes place exclusively when an aromatic aldehyde bears electron-donating groups at either the or position of the formyl group, while the cross-dehydrogenative coupling dominates in the absence of these groups.

-BuNI/KSO Mediated Csp-Csp Bond Cleavage - Transformylation from -Anisaldehyde to Primary Amides.

-BuNI/KSO mediated transformylation from -anisaldehyde to primary amides is reported. The mechanistic studies suggest the reaction occurs via a single electron transfer pathway. Based on the DFT electronic structure calculations of various reaction pathways, the most plausible mechanism involves the formation of a phenyl radical cation and an arenium ion as the key intermediates.

ICl-Mediated Functional Group Interconversion from Methyl Homopropargyl Ether to α-Iodo-γ-chloroketone.

An ICl-mediated highly chemo- and regioselective functional group interconversion from methyl homopropargyl ether to α-iodo-γ-chloro-ketone is reported. Density functional theory (DFT)-calculated reaction coordinate and potential energy surface support the high chemo-selectivity observed for the formation of α-iodo-γ-chloroketone over furan. The five-membered oxonium ring formation-ring opening mechanism is a potential template for the preparation of polyfunctionalized carbonyl compounds.