The Kolbe or Non‐Kolbe electrolysis is one of the most studied electro‐organic reactions and a fundamental pillar of organic chemistry. In contrast to classical Kolbe dimerization of monocarboxylic acids, dicarboxylic acids are only scarcely subject for Kolbe electrolysis in the literature despite their vast natural abundance. Herein, we report on the intramolecular biradical recombination of dicarboxylic acids as a green way to prepare alkenes or alkynes over a newly proposed mechanistic route. Proceeding over a radical mechanism without dimerization, it clearly stands out from classical (Non‐)Kolbe electrolysis. In the presence of non‐toxic aqueous solvents, the desired products form in excellent yields (up to 83 %), which are the highest reported for this substrate class. Once feasibility had been shown for the electrolysis of methylsuccinic acid, we could demonstrate its application to a broad scope of different dicarboxylic acids.

Eight new zinc complexes of bisguanidine ligands have been structurally characterised and tested for the polymerisation of lactide. Initially this necessitated the preparation of the new six bisguanidine ligands [TMG 2 thf, DMEG 2 thf, trans-TMG 2 (1,2)ch, trans-DMEG 2 (1,2)ch, R,R-TMG 2 (1,2)ch, R,R-DMEG 2 (1,2)ch]. With these ligands in hand, zinc chlorido complexes could be obtained, which were characterized by X-ray crystallography and NMR spectroscopy. Furthermore, two new zinc chlorido complexes are reported, based on previous bisguanidine ligands [TMG 2 (1,3)ch, DMEG 2 (1,3)ch]. All complexes show a distorted tetrahedral coordination geometry. These eight complexes are utilised as catalysts in melt polymerization

Abstract:Three new zinc complexes with monoamine-guanidine hybridligands have been prepared, characterized by X-ray crystallography and NMR spectroscopy, and tested in the solvent-free ring-opening polymerization of rac-lactide. Initially the ligands were synthesized from camphoric acid to obtain TMGca and DMEGca and then reacted with zinc(II) halides to form zinc complexes. All complexes have a distorted tetrahedral coordination. They were utilized as catalysts in the solvent-free polymerization of technical rac-lactide at 150 • C. Colorless polylactide (PLA) can be produced and after 2 h conversion up to 60% was reached. Furthermore, one zinc chlorido complex was tested with different qualities of lactide (technical and recrystallized) and with/without the addition of benzyl alcohol as a co-initiator. The kinetics were monitored by in situ FT-IR or 1 H NMR spectroscopy. All kinetic measurements show first-order behavior with respect to lactide. The influence of the chiral complexes on the stereocontrol of PLA was examined. Moreover, with MALDI-ToF measurements the end-group of the obtained polymer was determined. DFT and NBO calculations give further insight into the coordination properties. All in all, these systems are robust against impurities and water in the lactide monomer and show great catalytic activity in the ROP of lactide.

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