Electrophilic aromatic substitution (EAS) can provide a straightforward approach to the efficient synthesis of functionalized complex aromatic molecules. In general, Lewis acids serve as a beneficial stimulus for the formation of a Wheland complex, the intermediate in the classical SEAr mechanism of EAS, which is responsible for H/E (E=electrophile) substitution under formal H+ elimination. Herein, we report an unusual variant of EAS, in which a complex molecule such as the tricyanomethane, HC(CN)3, is activated with a strong Lewis acid (B(C6F5)3) to the point where it can finally be used in an EAS. However, the Lewis acid here causes the isomerization of the tricyanomethane to the ketenimine, HN=C=C(CN)2, which in turn directly attacks the aromatic species in the EAS, with simultaneous proton migration of the aromatic proton to the imino group, so that no elimination occurs that is otherwise observed in the SEAr mechanism. By this method, it is possible to build up amino‐malononitrile‐substituted aromatic compounds in one step.

Homoleptic cyanide compounds exist of almost all main group elements. While the alkali metals and alkaline earth metals form cyanide salts, the cyanides of the lighter main group elements occur mainly as covalent compounds. This review gives an overview of the status quo of main group element cyanides and cyanido complexes. Information about syntheses are included as well as applications, special substance properties, bond lengths, spectroscopic characteristics and computations. Cyanide chemistry is presented mainly from the field of inorganic chemistry, but aspects of chemical biology and astrophysics are also discussed in relation to cyano compounds.