Hypervalent Iodine Compounds with Carboxylate and Tetrazolate Ligands

In modern organic chemistry, hypervalent (HV) iodine(III) compounds are frequently used as oxidizing agents but application of λ3-iodanes in polymer and material chemistry is still underexplored. This dissertation describes the preparation of dynamic and self-healing materials by employing ligand exchange reactions involving HV iodine(III) compounds of the type ArIL2 (Ar = Aryl, L = ligand, e.g., carboxylate or (pseudo)halide). These compounds can undergo ligand exchange reactions in presence of nucleophiles (Nu-) to form ArINu2. Diacetoxyiodo benzene was successfully employed as a crosslinker to prepare dynamic and self-healing gels derived from carboxylate-containing polymers. Furthermore, advantage was taken of the ability of diacetoxyiodo benzene to generate radicals upon UV light irradiation in order to convert the dynamic crosslinked structures to permanent (set) networks. Star polymers were prepared by mixing block copolymers Sty/MMA and AA with diacetoxyiodo benzene solution. The star polymers were characterized by dynamic light scattering and diffusion ordered NMR spectroscopy. Besides that, oligomeric and µ-oxo- HV iodine(III) compounds with two I-N bonds, containing 5-substituted tetrazoles as the ligands PhI(N4CR)2 (R = C6H5, and 4-CH3C6H4) were synthesized using PhIO. The crystal structure of one representative compound (an oligomer with three I atoms in the backbone and 5-phenyltetrazole end groups) was solved and refined from synchrotron powder X-ray diffraction. The novel compounds were characterized by cyclic voltammetry and were found to be strong oxidants. An attempt was made to prepare tetrazole based polymer networks. After synthesizing tetrazole containing oligomeric HV iodine(III) compounds, N-heterocycle-stabilized pseudocyclic λ3-iodane with tetrazole as the stabilizing group was synthesized and its thermal stability and redox activity were studied. The oxidative power of the polyvalent iodine compound with a tetrazole ligand was demonstrated by conducting oxidation of thioanisole to sulfoxide and dimerization of thiobenzamide to 3,5-diphenyl-1,2,4-thiadiazole

Hypervalent Iodine Compounds with Carboxylate and Tetrazolate Ligands

In modern organic chemistry, hypervalent (HV) iodine(III) compounds are frequently used as oxidizing agents but application of λ3-iodanes in polymer and material chemistry is still underexplored. This dissertation describes the preparation of dynamic and self-healing materials by employing ligand exchange reactions involving HV iodine(III) compounds of the type ArIL2 (Ar = Aryl, L = ligand, e.g., carboxylate or (pseudo)halide). These compounds can undergo ligand exchange reactions in presence of nucleophiles (Nu-) to form ArINu2. Diacetoxyiodo benzene was successfully employed as a crosslinker to prepare dynamic and self-healing gels derived from carboxylate-containing polymers. Furthermore, advantage was taken of the ability of diacetoxyiodo benzene to generate radicals upon UV light irradiation in order to convert the dynamic crosslinked structures to permanent (set) networks. Star polymers were prepared by mixing block copolymers Sty/MMA and AA with diacetoxyiodo benzene solution. The star polymers were characterized by dynamic light scattering and diffusion ordered NMR spectroscopy. Besides that, oligomeric and µ-oxo- HV iodine(III) compounds with two I-N bonds, containing 5-substituted tetrazoles as the ligands PhI(N4CR)2 (R = C6H5, and 4-CH3C6H4) were synthesized using PhIO. The crystal structure of one representative compound (an oligomer with three I atoms in the backbone and 5-phenyltetrazole end groups) was solved and refined from synchrotron powder X-ray diffraction. The novel compounds were characterized by cyclic voltammetry and were found to be strong oxidants. An attempt was made to prepare tetrazole based polymer networks. After synthesizing tetrazole containing oligomeric HV iodine(III) compounds, N-heterocycle-stabilized pseudocyclic λ3-iodane with tetrazole as the stabilizing group was synthesized and its thermal stability and redox activity were studied. The oxidative power of the polyvalent iodine compound with a tetrazole ligand was demonstrated by conducting oxidation of thioanisole to sulfoxide and dimerization of thiobenzamide to 3,5-diphenyl-1,2,4-thiadiazole

Heterocyclic Hypervalent Iodine(III) Compounds with Fused Benziodazole and Tetrazole Rings (I-Substituted Tetrazolo[1,5-b][1,2]Benziodazoles)

A series of heterocyclic hypervalent (HV) iodine(III) compounds containing fused tetrazole and benziodazole rings, i.e., derivatives of benziodazolotetrazole (BIAT) with various ligands attached to the iodine atom were prepared and studied. BIAT-Cl was synthesized via chlorination of 5-(2-iodophenyl)-1H-tetrazole and subsequent spontaneous cyclo-dehydrochlorination of the initially formed dichloroiodo compound. The oxidation of the aforementioned parent monovalent iodine substrate with NaIO4 yielded BIAT-OH, which was in turn reacted with acetic anhydride to afford the I-acetoxy derivative BIAT-OAc. BIAT-OMe was obtained by refluxing the latter compound or by dissolving (2-(1H-tetrazol-5-yl)phenyl)(hydroxy)iodonium tosylate in methanol. All heterocyclic HV iodine(III) compounds were characterized by 1H and 13C NMR spectroscopy, ESI-HRMS, and single crystal X-ray crystallography. The reaction of alkenes with BIAT-Cl in the presence of Cu(OTf)2 at room temperature afforded chloro-tetrazolylated products in 70-88% isolated yields. The oxidation of thioanisole with BIAT-Cl under various reaction conditions is also reported. The thermal stabilities of all BIAT derivatives were examined as well. The enthalpies of exothermic degradation were measured by thermal gravimetric analysis coupled with differential scanning calorimetry and were determined to be in the range between −35.3 and −305.3 kJ mol-1, i.e., significantly larger than the enthalpy of decomposition (−29.4 kJ mol-1) of the parent monovalent iodine-containing tetrazole – 5-(2-iodophenyl)-1H-tetrazole