Combining the new aromatic bis(guanidine) ligand bis(tetramethylguanidino)toluene (TMG2tol) and different copper salts led to four new complexes. The molecular structures were analysed by X‐ray diffraction. Three of the complexes are active in biomimetic activation of oxygen. It is the first time a bis‐µ‐oxido species of an aromatic guanidine copper complex is analysed by Raman and UV/Vis spectroscopy. The formation and decay of the bis(µ‐oxido)dicopper species were investigated at low temperatures up to 273 K by UV/Vis spectroscopy with a stopped‐flow setup. The results showed that the Cu2O2 intermediate of an aromatic guanidine–copper complex decays much faster than most known bis(guanidine) complexes. Moreover, natural bond orbital (NBO) analyses revealed that the aromatic guanidine is the stronger donor compared to the aliphatic one.

We present a new approach to disubstituted diamondoids from corresponding carboxylic acids. A dirhodium‐acetate‐catalyzed (1 mol‐%) nitrene insertion reaction of sulfamides was, for the first time, applied to intramolecular C–H functionalization reactions of rigid tricyclic frameworks. This straightforward approach enables the effective and regioselective synthesis of a variety of diamondoid‐based cyclic sulfamidates, which are synthetically valuable building blocks. Reductive deprotection of the sulfamidate moiety leads to corresponding 1,3‐amino alcohol derivatives. Oxidation of the sulfamidate moiety by KMnO4 provides access to 1,3‐keto alcohols or imines. Finally, we report the synthesis of Vildagliptin® analogues as new antidiabetic drug candidates (DPP‐4 inhibitors).

Copper guanidine quinolinyl complexes act as good entatic state models for the electron transfer due to a high similarity between the corresponding Cu(i) and Cu(ii) complexes. The introduction of substituents leads to a further enhancement.

Bis(guanidine) copper complexes are known for their ability to activate dioxygen. Unfortunately, until now, no bis(guanidine) copper-dioxygen adduct has been able to transfer oxygen to substrates. Using an aromatic backbone, fluorescence properties can be added to the copper(I) complex which renders them useful for later reaction monitoring. The novel bis(guanidine) ligand DMEG2tol stabilizes copper(I) and copper(II) complexes (characterized by single crystal X-ray diffraction, IR spectroscopy, and mass spectrometry) and, after oxygen activation, bis(µ-oxido) dicopper(III) complexes which have been characterized by low-temperature UV/Vis and Raman spectroscopy. These bis(guanidine) stabilized bis(µ-oxido) complexes are able to mediate tyrosinase-like hydroxylation activity as first examples of bis(guanidine) stabilized complexes. The experimental study is accompanied by density functional theory calculations which highlight the special role of the different guanidine donors.

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