Rapid aerobic iodination of arenes mediated by hypervalent iodine in fluorinated solvents

Metal-free iodination of arylaldehydes for total synthesis of aristogins A-F and hernandial

Iodine is one of the most effective sources for iodination of aromatic compounds; however, its electrophilicity is insufficient for direct iodination. The selection of appropriate environmentally friendly and cost-effective oxidants in combination with iodine for the iodination of aromatic rings, along with its application in the synthesis of natural products, holds significant importance. A highly efficient method utilizing I(III) as the initiator has been successfully developed for monoiodination of arylaldehydes. The method demonstrates good compatibility with a wide range of (hetero)aromatic aldehydes, resulting in moderate to excellent yields, without the need for any toxic, volatile or explosive reagents. The synthesis of seven natural products, namely aristogins A-F and hernandial, was achieved through this iodination followed by Ullmann-type coupling.

A Green Alternative for the Direct Aerobic Iodination of Arenes Using Molecular Iodine and a POM@MOF Catalyst

Iodoarenes are important precursors for fine chemicals and pharmaceuticals. The direct iodination of arenes using molecular iodine (I₂) has emerged as an attractive green synthesis method. Most of the direct iodination protocols are still homogeneous systems that require harsh conditions and use or produce toxic products. We report a new heterogeneous catalytic route for the direct aerobic iodination of arenes under mild conditions using a PMoV₂ polyoxometalate (POM) embedded in the metal-organic framework (MOF) MIL-101 (PMoV₂@MIL-101). The catalyst shows full yield for the conversion of mesitylene to 2-iodomesitylene at a rate that is similar to the homogeneous POM system. Moreover, the catalyst is applicable for a wide range of substrates in an oxygen atmosphere without using any co-catalysts or sacrificial agents. To the best of our knowledge, this is the first report on designing a sustainable and green MOF-based heterogeneous catalytic system for the direct iodination reaction using molecular oxygen and iodine.

Hypercoordinate iodine for catalytic asymmetric diamination of styrene: insights into the mechanism, role of solvent, and stereoinduction

Stereoselectivity in the asymmetric diamination of styrene catalyzed by chiral hypercoordinate iodine originates from the prochiral face recognition when the substrate binds to the catalyst.

Hypercoordinate iodine has evolved as an impressive class of catalysts for various organic transformations. Extension of this idea to asymmetric applications, such as in the asymmetric difunctionalization of styrene or its derivatives, constitutes an important reaction. In this study, the mechanism and origin of stereoinduction in styrene diamination, with a sulfonimide (HNMs₂) as the diaminating agent and iodoresorcinol (((iPr)₂N(CO)-CH(Me)-O)₂Ar–I) based chiral hypercoordinate iodine as the catalyst, are investigated using density functional theory calculations. The energetically preferred catalytic pathway has been found to involve, among other steps, two very important mechanistic events: (a) the formation of a catalyst–substrate complex by the action of styrene on the catalyst ArI(NMs₂)₂, resulting in the displacement of one of the imidates (NMs₂^–); and (b) a rebound of the departed imidate on the iodine-bound styrene to form an iodonium ion intermediate with a N–C bond. Explicit interaction of the imidate ion with hexafluoroisopropanol (HFIP), used as a solvent additive, lowers the barrier for the formation of the iodonium ion. The P helical fold of the chiral arms of the iodoresorcinol catalyst is found to offer a chiral environment for the reactants. Coordination of the iodine catalyst to the styrene double bond is found to make the benzylic carbon more electrophilic and hence makes it the preferred site for the nucleophilic addition. In the chiral environment of the catalyst, an enhanced polarization of the styrene double bond is noticed when the double bond coordinates through the si prochiral face than the re face. Nucleophilic addition on the re face of the catalyst–substrate complex is associated with a lower activation barrier leading to the experimentally observed S enantiomeric product. The stereoselective model developed in this study can be employed to related asymmetric styrene difunctionalizations using similar hypercoordinate iodine catalysts.

2,2-Diiododimedone: a mild electrophilic iodinating agent for the selective synthesis of α-iodoketones from allylic alcohols

In combination with an iridium catalyst, a new electrophilic iodinating agent enables the synthesis of α-iodocarbonyls from allylic alcohols.