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M. Schnürch, M. Spettel:
"An old dog with new tricks: quaternary ammonium salts as operationally simple alkylating agents in C-H activation chemistry";
Poster: 20th European Symposium on Organic Chemistry, Köln; 02.07.2017 - 06.07.2017; in: "Programme 20th European Symposium on Organic Chemistry", (2017), S. 96.

Metal catalysed C-H activation chemistry has established itself as an attractive alternative to the well-known cross-coupling reactions. [1] An important reason for this is the increased atom efficiency, which bears the potential for overall more efficient synthesis of valuable compounds. Many different reactions have been realized using C-H activation chemistry such as arylation, amidation, alkenylation or alkylation, to name only a few. The latter method often relies on alkenes as the alkyl source, which brings about a few limitations. [2],[3] Most importantly, short chained alkenes are gaseous and hence such reactions have to be carried out using special equipment compatible with high pressures. So for the most simple alkylations (e.g. ethylation and propylation), the most experimental effort is required.

Thinking about an operationally more simple protocol, we considered in situ formation of the olefine from a suitable substrate, which should be crystalline at room temperature and only release the olefine in course of the reaction. The simple solution was using quaternary ammonium salts, which form olefins via the well-known Hofmann elimination.

C-H activation, Hofmann elimination, quarternary ammonium salts, alkylation