The activation of diazo compounds by nitrogen extrusion in the presence of transition-metal complexes is a convenient method for the transfer of a carbene to an organic substrate in, for example,[2+ 1] cycloadditions with olefins [1] or carbonyl compound [2] to give three- membered-ring compounds, or in reactions with electron-rich heteroatoms like sulfur,[3] phosphorus,[4] and nitrogen [5] to generate ylides.[6] In general, these types of reactions ...