Neues aus der Chemie der Iminiumsalze

Recent Developments in Iminium Salt Chemistry Iminium salts are of continuing interest as versatile building blocks in organic synthesis. This progress report from different laboratories highlights some current research activities in iminium salt chemistry. Several contributions focus on novel synthetic applications of isolable, functionalized iminium systems such as α,β-unsaturated iminium salts (e.g. vinamidinium, 3-trifloxy, 3-chloro-, 3-isocyanato- and 3-thiopropene iminium, as well as propyne iminium salts), furthermore on phosgene iminium chloride and trifluoromethyl-substituted iminium salts. Iminium intermediates occur in various synthetic transformations; for example, cyclopropane iminium ions are intermediates in nucleophilic substitution reactions at bicyclic aminocyclopropanes. Also reported is the synthesis of a variety of novel orthoamides and their use as synthetic building blocks. Research directed to the application of vinamidinium salts in materials science is also presented.