The present review casts light on the main strategies for the synthesis of fused heterocycles by metal-mediated [2+2+2] cyclotrimerization of alkynes and/or nitriles as well as their specific syntheses. A number of other reviews that have appeared, concerning [2+2+2] cyclotrimerization of alkynes and or nitriles to fused heterocycles, did not pay special attention to the synthesis of such systems in an organized manner with respect to the type of the heterocyclic systems.
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