Design and Synthetic Applications of High Oxidation State Iodine and Gold Complexes

A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Agriculture, Biomedicine and Environment, La Trobe University, Victoria, Australia. </p

Synthesis and Structural Verification of an ArI(OTf)2, NO2-Ph-I(OTf)2

PhI(OTf)2 and related ArI(OTf)2 species have been incorrectly invoked as intermediates in oxidation reactions for many years. We recently established that such compounds did not yet exist but remain an attractive target. Here we describe the synthesis, isolation, and structural characterization of NO2-PhI(OTf)2, which is resistant to decomposition and more reactive than PhI(OTf)(OAc), the species previously misidentified as PhI(OTf)2

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.</p

Synthesis, structural characterization, reactivity and catalytic activity of mixed halo/triflate ArI(OTf)(X) species

Both mixed λ3-iodoarenes and λ3-iodoarenes possessing -OTf ligands are coveted for their enhanced reactivities. Here we describe the synthesis, reactivity, and comprehensive characterisation of two new ArI(OTf)(X) species, a class of compound that were previously only invoked as reactive intermediates where X = Cl, F and their divergent reactivity with aryl substrates. A new catalytic system for electrophilic chlorination of deactivated arenes using Cl2 as the chlorine source and ArI/HOTf as the catalyst is also described.</p

Reactivity studies of cationic Au(III) difluorides supported by N ligands

The reactivity of difluoro Au(III) cations supported by pyridine or imidazole ligands is reported. The Au(III)−F bond is found to be susceptible to metathesis by TMS reagents and reagents bearing acidic protons such as H−CC−Ph and HOAc. In the last case the reactions are slower than analogous reactions reported by other groups, where strong trans donors are present opposite the Au−F bond. This, coupled with the inability to effect metathesis on only one Au−F bond in our system, indicates that the trans effect is a key consideration in Au−F chemistry

Structural verification and new reactivity for Stang's reagent, [PhI(CN)][OTf]

The structure of Stang's reagent [PhI(CN)][OTf] is confirmed by X-ray crystallography and is determined to be best described as an ion-pair in organic solution. It is found to be a strong Lewis acid, but reaction with pyridine ligands gives [Pyr-CN][OTf] salts via oxidation of pyridine giving a new derivative of the CDAP reagent widely used as an activation agent for polysaccharides.</p

On the potential intermediacy of PhIBr2 as a brominating agent

No description supplied </p

Lewis acid activation of Weiss' reagents ([PhI(Pyr)2]²⁺) with boranes and isolation of [PhI(4-DMAP)]²⁺

Abstraction of a pyridine ligand from Weiss' reagent ([PhI(Pyr)2]2+) using BF3-Et2O was found to activate Weiss' reagent towards electrophilic aromatic substitution reactions. The activated species can be isolated when 4-DMAP is used as the pyridine ligand and was determined to be [PhI(4-DMAP)]2+ in solution. The isolated cation was reactive in electrophilic aromatic substitution reactions towards mesitylene, xylene and toluene that Weiss' reagent itself does not react with.</p

PhI(OTf)2 Does Not Exist (Yet)

PhI(OTf) has been used for the past 30 years as a strong I(III) oxidant for organic and inorganic transformations. It has been reported to be generated in situ from the reactions of either PhI(OAc) or PhI=O with two equivalents of trimethylsilyl trifluoromethanesulfonate (TMS-OTf). In this report it is shown that neither of these reactions generate a solution with spectroscopic data consistent with PhI(OTf) , with supporting theoretical calculations, and thus this compound should not be invoked as the species acting as the oxidant for transformations that have been associated with its use.</p

PhI(OTf)2 Does Not Exist (Yet)

PhI(OTf) has been used for the past 30 years as a strong I(III) oxidant for organic and inorganic transformations. It has been reported to be generated in situ from the reactions of either PhI(OAc) or PhI=O with two equivalents of trimethylsilyl trifluoromethanesulfonate (TMS-OTf). In this report it is shown that neither of these reactions generate a solution with spectroscopic data consistent with PhI(OTf) , with supporting theoretical calculations, and thus this compound should not be invoked as the species acting as the oxidant for transformations that have been associated with its use.</p