Readily prepared N-aminopyridinium salts are valuable precursors for the generation of N-centered radicals. Reduction of these salts by single electron transfer allows for clean generation of amidyl radicals. It is shown that direct radical C-H amination of heteroarenes and arenes can be achieved with N-aminopyridinium salts under mild conditions by using photoredox catalysis.

New P/N-containing π-electron systems comprising fully planar biaryl arrays are synthesized by multiple radical phosphanylation. The biaryl moiety in these highly strained planar π-systems is rigidified by double P-bridging. The electronic properties of the core biaryl entity are varied by introducing N-donor substituents or by installing N-atoms within the π-system, thereby moving to the viologen core structure. The electrochemical and photophysical properties of these compounds are discussed and compared with those of related systems.

Ladder π-conjugated materials and also push-pull systems belong to important classes of compounds for the development of organic electronic devices. In this communication, a novel π-conjugated material that unifies the properties of both of these classes is presented. The material comprises a rigid biphenyl framework, which bears two bridging electron-accepting phosphine oxide moieties as well as two electron-donating amino groups. The structure and photophysical properties of this compound are discussed and compared with those of a related system lacking the second P-moiety.

Heteroarenes. -By means of photoredox catalysis under mild conditions arenes and hetarenes are amidated. Whereas most substrates, including 1,4-disubstituted arenes, indole and pyrrole derivatives as well as furan, are transformed regioselectively, mono-substituted arenes such as toluene and anisole as well as thiophene form mixtures of regioisomers. -(GREULICH, T. W.; DANILIUC, C. G.; STUDER*, A.; Org. Lett. 17 (2015) 2, 254-257, http://dx.