A flow-metallaelectro-catalyzed C–H activation was realized in terms of robust rhodaelectro-catalyzed alkyne annulations. To this end, a modular electro-flow cell with a porous graphite felt anode was designed to ensure efficient turnover. Thereby, a variety of C–H/N–H functionalizations proved amenable for alkyne annulations with high levels of regioselectivity and functional group tolerance, viable in both an inter- or intramolecular manner. The electro-flow C–H activation allowed easy scale up, while in-operando kinetic analysis was accomplished by online flow-NMR spectroscopy. Mechanistic studies suggest an oxidatively induced reductive elimination pathway on rhodium­(III) in an electrocatalytic regime.

The iron-catalyzed hydroarylation of allenes was accomplished by weak phenone assistance. The C–H activation proceeded with excellent efficacy and high ortho-regioselectivity in proximity to the weakly coordinating carbonyl group for a range of substituted phenones and allenes. Detailed mechanistic studies, including the isolation of key intermediates, the structural characterization of an iron–metallacycle, and kinetic analysis, allowed the sound elucidation of a plausible catalytic working mode. This mechanistic rationale is supported by detailed computational density functional theory studies, which fully address multi-spin-state reactivity. Furthermore, in operando nuclear magnetic resonance monitoring of the catalytic reaction provided detailed insights into the mode of action of the iron-catalyzed C–H alkylation with allenes.

In light of the current energy requirements, the conversion of CO2 and N2 into useful C–N bond-containing products under mild conditions has become an area of intense research. However, the inert nature of N2 and CO2 renders their coupling extremely challenging. Herein, nitrogen and carbon atoms originating from N2 and CO2, respectively, are fixed sequentially by NbH2 – anions in the gas phase at room temperature. Isocyanate and NbO2CN– anions were formed under thermal collision conditions, thus achieving the formation of new C–N bonds directly from simple N2 and CO2. The anion structures and reaction details were studied by mass spectrometry, photoelectron spectroscopy, and quantum chemical calculations. A novel N2 activation mode (metal–ligand activation, MLA) and a related mechanism for constructing C–N bonds mediated by a single non-noble metal atom are proposed. In this MLA mode, the C atom originating from CO2 serves as an electron reservoir to accept and donate electrons.

A ruthenium‐catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation of various bridgehead N‐fused [5,6]‐bicyclic heteroarenes through regioselective electrochemical C−H/N−H annulation without chemical metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive of an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime.

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