Recent Progress in Metal-Catalyzed [2+2+2] Cycloaddition Reactions

Abstract Metal-catalyzed [2+2+2] cycloaddition is a powerful tool that allows rapid construction of functionalized 6-membered carbo- and heterocycles in single step through an atom-economical process with high functional group tolerance. The reaction usually regio- chemoselective although selectivity issues can still be challenging for intermolecular reactions involving the cross-[2+2+2] two or three different alkynes various strategies have been developed to attain selectivities. Furthermore, enantioselective efficient means create central, axial, planar chirality variety chiral organometallic complexes used asymmetric transition-metal-catalyzed inter- intramolecular reactions. This review summarizes recent advances field cycloaddition. 1 Introduction 2 Formation Carbocycles 2.1 Intermolecular Reactions 2.1.1 Cyclotrimerization Alkynes 2.1.2 Cycloaddition Two Different 2.1.3 Alkynes/Alkenes Alkenes/Enamides 2.2 Partially Intramolecular 2.2.1 Rhodium-Catalyzed 2.2.2 Molybdenum-Catalyzed 2.2.3 Cobalt-Catalyzed 2.2.4 Ruthenium-Catalyzed 2.2.5 Other Metal-Catalyzed 2.3 Totally 3 Heterocycles 3.1 Nitriles 3.2 1,6-Diynes Cyanamides 3.3 Selenocyanates 3.4 Imines Allenes Alkenes 3.5 (Thio)Cyanates Isocyanates 3.6 1,3,5-Triazines 3.7 Aldehydes Enynes Allenes/Alkenes 3.8 4 Conclusion