Available strategies for the synthesis of indenes for metal complex catalysis

Simple and available methods for the synthesis of indene derivatives, mainly alkyl- and aryl-substituted indenes, which are most sought after as ligands for the development of catalysts based on transition metal complexes, are summarized. The review covers synthetic approaches including both the assembly of the indene structure from acyclic or monocyclic precursors and the functionalization of the indene framework or related compounds, such as benzofulvenes, indanones, indanes, indenones, fluorenes, etc. However, we excluded from our consideration the multi-step synthetic pathways and those which require commercially unavailable precursors and reagents.