Catalytic Metathesis Reaction in Organic Synthesis

Olefin metathesis is one of the most fascinating reac­ tions in the realm of catalysis. It is a remarkable catalytic reaction in which two olefins undergo bond reorganization leading to the redistribution of alky­ lidene moieties (Eqn 1 ). Chauvin et al. la postulated that olefin metathesis proceeds by a [2+2] cycloaddition between the metal alkylidene moiety and the olefinic substrate to pro­ duce a metallocyclobutane intermediate and subse­ quently, cycloreversion occurs to afford a new metal alkylidene and the olefinic product (Eqn 2). In this process the fundamental steps are frequently reversi­ ble and the reaction is under thermodynamic control. This process does not proceed under stereocontrol, and lead to the formation of regioisomeric mixture of olefinic products. Olefin metathesis reaction involves both the cleav­ age and the formation of C-C double bonds. A variety of homogeneous and heterogeneous catalysts are known to effect the olefin metathesis reaction and has many varied chemical applications. Recently this re­ action was applied to various carbocycles and hetero­ cycles.