Amine derivatives prepared from camphoric acid were used as ligands for the synthesis of corresponding copper(I) complexes. Their reactivity towards dioxygen was analyzed. The formation of a short-lived bis(μ-oxido)copper complex was spectroscopically observed during the reaction of the copper(I) complex with (1R, 3S)-N 1 ,N 1 ,N 3 ,N 3 -Tetramethyl-1,2,2-trimethylcyclopentane-1,3-diamine as a ligand. Furthermore, a regioselective demethylation of the ligand system was detected.Deuteration of the methyl groups of the ligand allowed crystallization and characterization of the bis(μ-oxido)copper complex. Derivatives of the ligand with pyridine residues caused suppression of the reactivity of the corresponding copper(I) complexes towards dioxygen. Additionally, the ligand system could be modified for intramolecular oxygenation reactions with benzaldehyde that led to the formation of salicylaldehyde, a selective hydroxylation in ortho position.

The present study describes the kinetic analysis of the 3chloropiperidine alkylation mechanism. These nitrogen mustard-based compounds are expected to react via a highly electrophilic bicyclic aziridinium ion, which is readily attacked by nucleophiles. Halide abstraction using silver salts with weakly coordinating anions lead to the isolation of these proposed intermediates, whereas their structure was confirmed by single crystal XRD. Kinetic studies of the aziridinium ions also revealed notable reactivity differences of the C5 gem-methylated compounds and their unmethylated counterparts. The observed reactivity trends were also reflected by NMR studies in aqueous solution and DNA alkylation experiments of the related 3-chloropiperidines. Therefore, the underlying Thorpe-Ingold effect might be considered as another option to adjust the alkylation activity of these compounds.

The reaction of dioxygen with copper(I) complexes containing camphor-derived ligands was investigated. Stopped-flow measurements revealed the formation of bis(μ-oxido) copper complexes at low temperatures. However, these intermediates were not stable enough to be isolated and decomposed quickly. Sterically more demanding alkyl groups slowed the formation of the bis(μ-oxido) copper complexes. A kinetic analysis was performed and showed -in line with previous reports -that the rate-determining step could be assigned to forming a mono-nuclear superoxido copper complex. For one of the reactions investigated, a product could be structurally characterized and turned out to be a copper(II) complex with an additional hydroxide as a ligand (most likely caused by a CÀ H abstraction from the solvent acetone). One of the complexes oxidized thioanisole to the corresponding sulfoxide (conversion of 34 % according to GC-MS) with no byproducts. Chiral GC gave an enantiomeric excess of 14 %.

The Front Cover shows the reaction of dioxygen with a copper(I) complex containing a tetramethylated diamine ligand that is related to camphor. The formation of a short‐lived bis(μ‐oxido) copper complex was observed spectroscopically by low temperature stopped‐flow kinetics. Deuteration of the methyl groups enabled crystallization and structural characterization of this reactive intermediate. More information can be found in the Full Paper by R. Göttlich, S. Schindler and co‐workers.

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