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Coupling diazo compounds with copper bronze (ultra fine copper powder). It exactly looks like glitter powder in the flask. 

Even through it was a heterogeneous reaction (the reaction took only place at the surface of the copper) a relatively high percent of the desired product formed. Good point: the side product could be removed easily via distillation, so this was a quite easy method for producing a compound. Copper and other transition metals are often used as catalyst for coupling reactions, the most popular is palladium, it is good for everything.