Recent Developments in Cyclopropane Cycloaddition Reactions

Cycloaddition reactions of cyclopropane derivatives have been widely used in the rapid construction of cyclic, polycyclic, or bridged cyclic products; asymmetric synthesis of cyclic frameworks; and building blocks for natural products. Cyclopropane cycloadditions can merge photoredox catalysis, C–H bond activation, and radical cascade processes to establish new cycloaddition modes, demonstrating the usefulness in the exploration of new synthetic methods. Along with the ring-opening of cyclopropane by a variety of catalytic systems, it can be readily used as two- to seven-carbon synthons for various cycloaddition reactions. In organic synthesis, the synthetic methodology of using cyclopropanes for cycloadditions has witnessed significant progress over the past several years. A series of cyclopropane-related cycloaddition reactions via organic or metal-catalyzed/mediated pathways has been exploited in constructing cyclic frameworks such as polycycles, bridged-ring carbocycles, and heterocycles. Moreover, this synthetic chemistry has also recently blossomed in the pursuit of highly efficient asymmetric cycloadditions, C–H bond-activated cycloadditions, photoredox catalysis-cooperated cycloadditions, and several other unique reaction processes. Although numerous cyclopropane-based cycloaddition reactions have been reported, the newly explored cycloadditions have not yet been reviewed. Herein, we present recent progress in cyclopropane-related cycloadditions over the past 6 years. In organic synthesis, the synthetic methodology of using cyclopropanes for cycloadditions has witnessed significant progress over the past several years. A series of cyclopropane-related cycloaddition reactions via organic or metal-catalyzed/mediated pathways has been exploited in constructing cyclic frameworks such as polycycles, bridged-ring carbocycles, and heterocycles. Moreover, this synthetic chemistry has also recently blossomed in the pursuit of highly efficient asymmetric cycloadditions, C–H bond-activated cycloadditions, photoredox catalysis-cooperated cycloadditions, and several other unique reaction processes. Although numerous cyclopropane-based cycloaddition reactions have been reported, the newly explored cycloadditions have not yet been reviewed. Herein, we present recent progress in cyclopropane-related cycloadditions over the past 6 years. an addition of a three-atom unit containing a π-system to the end of another two-atom π-system to afford a five-membered ring. a process including fragmentation of a ring skeleton and other processes to give a cycloadduct. a double bond that is connected to the external terminal of a ring structure. a cyclic compound that has atoms of at least two different elements as members of its ring(s). a radical redox relay sequence consists of a single-electron reduction, a radical addition, and radical oxidation processes. The electron transfer between an organic substrate and catalyst gets an overall redox-neutral result. a reagent that can act as two different building blocks upon treatment with the other reagent in a one-pot manner. a base-induced elimination by using vinylogous-hydroxysilanes to obtain the diene derivatives. a molecule that carries both a positive and a negative charge on two adjacent atoms.