Sustainability in Organic Synthesis - Bidentate Lewis Acid Inverse Electron-Demand Diels-Alder Reactions and the Synthesis of Organic Redox Flow Battery Electrolyte Materials

Abstract

Sustainable development in organic chemistry is driven by limited fossil raw materials, waste production and environmental pollution. The waste issue can be solved by catalysed one-step reactions, which are more sustainable than waste-producing multistep reactions. Since 2011, the Wegner group develops such reactions: the bidentate boron Lewis acid catalysed inverse electron-demand Diels-Alder (IEDDA) reaction of 1,2-diazines. In this thesis, the bidentate boron Lewis acid catalysed IEDDA reaction of phthalazines with substituted 2,3-dihydrofurans and 5-thioalkyl-2,3-dihydrofurans was investigated in an explorative study. The substitution pattern determined the subsequent rearrangement or elimination reaction to dihydronaphthalines or naphthofurans. In the second part of this thesis, the catalysed IEDDA reaction was used to synthesize organic redox material for organic redox flow batteries, which could store the generated energy of renewable power plants, and thus, circumvent carbon dioxide production from limited carbon feedstocks. To bypass these fossil raw materials as starting material, wood-derived vanillin was investigated as renewable and, thus, sustainable precursor for the synthesis of redox materials. The obtained vanillin-derived material and the diazaanthraquinones and 5,8-dihydroxyphthalazines, synthesized in the IEDDA reaction of 1,2,4,5-tetrazine and naphthoquinone/benzoquinone, were analysed via cyclic voltammetry regarding their electrochemical potentials and their stability. The vanillin-derived redox material showed the feasibility of synthesizing redox material from renewable sources. The diazaanthraquinones and 5,8-dihydroxyphthalazines were demonstrated as potential battery material. The 5,8-dihydroxyphthalazines surpassed the diazaanthraquinones with regard to their higher potentials and increased stability.