A Novel Method of Cyclization by Means of Alkene Metathesis: A Synthetic Strategy of Carbo- and Hetero-Cyclic Compounds.

Historical background of alkene metathesis is briefly reviewed. The introduction of the Schrock Mocarbene complex and the Grubbs Ru-carbene complexes has initiated rapid development of synthetic utility of alkene metathesis. Many functional groups are tolerated without protection in the Mo and Ru catalysed metathesis. Among several synthetic applications of the alkene metathesis, the ring closing metathesis offers an extremely useful method for cyclization to give carbo-and hetero-cyclic compounds from medium to large sizes. A number of naturally occurring macrocyclic compounds have been synthesized in shorter steps by the ring closing metathesis using the Ru complex as key reaction. The alkene metathesis has brought in a dramatic change in synthetic designs of complex cyclic compounds.