Regioselective Functionalization of 7‐Azaindole by Controlled Annular Isomerism: The Directed Metalation‐Group Dance

The regioselective functionalization of 7‐azaindole by controlled annular isomerism employing a directed metalation‐group migration is reported. The N7 carbamoyl azaindoles undergo regioselective metalation and quenching with an electrophile to furnish C6‐substituted derivatives which, in the presence of a catalytic amount of ClCONR₂ promotes a carbamoyl group shift or dance from N7 to N1. A second directed metalation/electrophile quench sequence leads to 2,6‐substituted azaindoles. Optimization of the metalation conditions for C2 and C6, separately and iteratively, is presented. Using the directed metalation group dance strategy, a late‐stage deuteration of an antipsychotic drug is described. Overall, the controlled migration of the carbamoyl directing group allows multiple functionalization events of the bioactive azaindole scaffold.     

Strain Coupling of Conversion‐type Fe3O4 Thin Films for Lithium Ion Batteries

Lithiation/delithiation induces significant stresses and strains into the electrodes for lithium ion batteries, which can severely degrade their cycling performance. Moreover, this electrochemically induced strain can interact with the local strain existing at solid–solid interfaces. It is not clear how this interaction affects the lithiation mechanism. The effect of this coupling on the lithiation kinetics in epitaxial Fe₃O₄ thin film on a Nb‐doped SrTiO₃ substrate is investigated. In situ and ex situ transmission electron microscopy (TEM) results show that the lithiation is suppressed by the compressive interfacial strain. At the interface between the film and substrate, the existence of Li_x Fe₃O₄ rock‐salt phase during lithiation consequently restrains the film from delamination. 2D phase‐field simulation verifies the effect of strain. This work provides critical insights of understanding the solid–solid interfaces of conversion‐type electrodes.