Rhodium-Catalyzed [2+2+2] Cycloaddition of Alkynes for the Synthesis of Substituted Benzenes: Catalysts, Reaction Scope, and Synthetic Applications

The transition-metal-catalyzed [2+ 2+ 2] cycloaddition of alkynes is a useful and atom-economical method for the synthesis of substituted benzenes. This comprehensive review covers the [2+ 2+ 2]-cycloaddition reactions catalyzed by rhodium complexes. Applications of the rhodium-catalyzed [2+ 2+ 2] cycloaddition in the synthesis of functional organic compounds are also described. 1 Introduction 2 [2+ 2+ 2]-Cycloaddition Reactions Catalyzed by Neutral Rhodium Complexes 2.1 Intermolecular Reactions 2.2 Intramolecular Reactions 3 [2+ 2+ 2]-Cycloaddition Reactions Catalyzed by Cationic Rhodium Complexes 3.1 Intermolecular Reactions 3.2 Intramolecular Reactions 4 Synthetic Applications 4.1 Synthesis of Cyclophanes 4.2 Synthesis of Biaryls 4.3 Synthesis of Organophosphorus Compounds 4.4 Synthesis of Helicene-Like Molecules 4.5 Synthesis of Complex Biologically Active Compounds 4.6 Synthesis of Organic Materials 5 Summary and Outlook