The activation of 2-(bromomethyl)benzaldehydes using N-heterocyclic carbenes represents a novel approach to the generation of o-quinodimethane (o-QDM) intermediates. Coupling with ketones such as phenylglyoxylates, isatins, or trifluoromethyl ketones via [4 + 2] annulation gives access to functionalized 1-isochromanones.

We present a combined electrochemical, kinetic, and synthetic study with a novel and easily accessible class of titanocene catalysts for catalysis in single-electron steps. The tailoring of the electronic properties of our Cp TiX-catalysts that are prepared in situ from readily available Cp TiX is achieved by varying the anionic ligand X. Of the complexes investigated, Cp TiOMs proved to be either equal or substantially superior to the best catalysts developed earlier. The kinetic and thermodynamic properties pertinent to catalysis have been determined. They allow a mechanistic understanding of the subtle interplay of properties required for an efficient oxidative addition and reduction. Therefore, our study highlights that efficient catalysts do not require the elaborate covalent modification of the cyclopentadienyl ligands.

In one word,h ow would you describe your research? Evolving, exciting, rewarding, dynamic! What is the most significant result of this study?Catalysis in single-electron steps merges the advantages of radical chemistry,s uch as high functional group tolerance, mild reaction conditions, and high rates, with those of transition-metal catalysis, such as control of stereoselectivity by the ligands of the metals. The key aspect of our approach is to perform oxidative additions and reductive eliminations in one-electron steps. Therefore, we make use of the same terms as in classical catalysis but significantly broaden the scope of old concepts. How is this approach related to other fields of catalysis?In many cross-coupling reactions and Lewis acid catalyzed processes the variation of the anionic ligands lead to an increase in reactivity and selectivity.F or catalysis in single-electron steps this is also the case. However,w ith cyclic voltammetry,w eh ave an ideal method that allows us to rationally screen the properties essential for reactivity.T his is not always straightforward in other branches of catalysis. Therefore, our approach is both related and unique.How did the collaborationo nt his project start?The collaboration started when Professors Gansäuer and Flowers met at an organic free radical conference in Ottawa in 2009. Since then they have tackled many mechanistic problems often with the aid of theoretical chemistry.

It takes an interplay of methods and an international collaboration to pick the best fruit of knowledge for catalysis in single‐electron steps from the titanocene anion tree! From a pool of potentially useful anionic ligands, mesylate was identified as most suitable for the generation of novel titanocene complexes that are excellent catalysts for sustainable radical arylations. The international cooperation featuring synthesis, cyclic voltammetry, and kinetics was essential for the success of our endeavor. More information can be found in the Full Paper by R. A. Flowers II, A. Gansäuer, et al. on page 6371.