Olefin Metathesis by First‐Row Transition Metals

Catalytic olefin metathesis based on the second‐ and third‐row transition metals has become one of the most powerful transformations in modern organic chemistry. The shift to first‐row metals to produce fine and commodity chemicals would be an important achievement to complement existing methods with inexpensive and greener alternatives. In addition, those systems can offer unusual reactivity based on the unique electronic structure of the base metals. In this Minireview, we summarize the progress of the development of alkylidenes and metallacycles of first‐row transition metals from scandium to nickel capable of performing cycloaddition and cycloreversion steps, crucial reactions in olefin metathesis. In addition, we will discuss systems capable of performing olefin metathesis; however, the nature of active species is not yet known. In this Minireview, alkylidenes and metallacyclobutanes of the first‐row metals capable of performing cycloaddition and cycloreversion reactions, the critical steps in olefin metathesis reactions, are discussed. Also, examples of olefin metathesis catalyzed by first‐row metal complexes are shown. The high abundance of base metals could potentially provide inexpensive and greener alternatives to existing methods.