PhICl2 is activated by chloride ions

A decade of lessons in the activation of ArIL2 species

Hypervalent iodine(iii) compounds of the general structure ArIL2 are widely used as oxidizing agents for a variety of applications across both organic and inorganic chemistry. Considerable work has been done on the activation of these compounds by tuning the ligands at the iodine centre. This perspective summarises the work of our and other groups on rectification of historically misidentified iodine(iii) reagents of this class, and the syntheses of activated species. Recent advances focusing on increasing the oxidative capacity of I(iii) moieties using Lewis and Brønsted acids and Lewis bases as well as the activation of halogens with I(iii) are discussed.

Electrophilic activation of molecular bromine mediated by I(III)

In pursuit of a genuine bromo-λ3-iodane, it has been found that the combination of Br2 and electron deficient λ3-iodanes can result in the delivery of both bromine atoms from Br2 to a range of aryl substrates, some highly deactivated. These brominations occur rapidly in common chlorinated solvents at room temperature and can be achieved with the catalytic activation of commercially available PhI(OAc)2 and PhI(OTFA)2. para-NO2 substituted derivatives are employed to direct bromination towards more deactivated substrates. The mechanism of Br2 activation is discussed with insights being made, however it remains unclear.

Kinetic study on the activation of PhICl2 with Lewis bases for aromatic chlorination

A study on the kinetics of the activation of PhICl₂ using catalytic chloride or pyridine in electrophilic chlorination of arenes has been carried out. The results indicate that both catalysts induce the release of Cl₂ from PhICl₂ and that the Cl₂ is the active reagent for chlorination in these reactions.

On the potential intermediacy of PhIBr2 as a brominating agent

PhIBr2 has been invoked as a brominating agent, however PhIBr2 does not appear to exist but rather forms PhI and Br2, with Br2 being responsible for bromination.

Catalytic role of amines in activation of PhICl2 from a computational point of view

We thoroughly investigated mechanistic features of dichlorination of diazoacetates using PhICl₂ catalysed by pyridine. We found that the pyridine serves as a catalyst for decomposition of PhICl₂ to PhI and Cl₂, leading to the dichlorination step being driven by the in situ generated Cl₂. This type of activation was found to be applicable to other amine-catalysed chlorination reactions using PhICl₂.