Gattermann-Koch reaction

The Gattermann-Koch reaction, named for the German chemists Ludwig Gattermann and Julius Arnold Koch, in organic chemistry refers to a Friedel-Crafts acylation reaction in which carbon monoxide and hydrochloric acid are used in-situ with Friedel-Crafts catalyst, namely AlCl3 to produce a benzaldehyde-derivative from a benzene-derivative in one step. Benzaldehyde and many aromatic aldehydes are conveniently synthesized by this reaction. Presence of traces of copper(I) chloride are also needed.