Recent synthetic studies towards natural products via [5 + 2] cycloaddition reactions

[5 + 2] Cycloaddition reactions have attracted increasing attention from the chemistry community owing to their utility in the field of natural product synthesis. Recently, a number of natural products with complex skeletons have been obtained with the use of [5 + 2] cycloaddition reactions. The effectiveness of these transformations can be attributed to the constant development of new methodologies and their ingenious applications in synthetic design. [5 + 2] Cycloaddition reactions are frequently followed by other operations, such as cyclocondensation and rearrangement reactions. A newly developed type II intramolecular [5 + 2] cycloaddition offers efficient and straightforward synthesis of many highly functionalized and synthetically challenging bridged cycloheptane bicyclic skeletons. This progress has expanded the scope of target synthetic structures achievable by [5 + 2] cycloadditions and enhanced the usefulness of these reactions in natural product synthesis. In this review, we provide a summary of recent progress regarding synthetic studies towards natural products via [5 + 2] cycloaddition reactions.