Eschweiler–Clarke reaction

The Eschweiler–Clarke reaction (also called the Eschweiler–Clarke methylation) is a chemical reaction whereby a primary (or secondary) amine is methylated using excess formic acid and formaldehyde. Reductive amination reactions such as this one will not produce quaternary ammonium salts, but instead will stop at the tertiary amine stage. It is named for the German chemist Wilhelm Eschweiler (1860–1936) and the British chemist Hans Thacher Clarke (1887–1972).