Tandem [4+2]/[3+2] Cycloadditions

This chapter focuses on tandem cycloadditions that are initiated by a [4 + 2] cycloaddition step that generates a 1,3‐dipole or a precursor to a 1,3‐dipole, which then engages in a [3 + 2] cycloaddition. Compared to the cycloadditions of nitroalkenes, tandem cycloadditions of 1,3,4‐oxadiazoles consist not of two, but of three elementary reactions. The major synthetic applications of the tandem cycloadditions of 1,3,4‐oxadiazoles include construction of oligomeric ribbon‐like or cavity molecules as well as syntheses of natural products. The chapter refines the definition of a tandem process and its three variants: cascade, consecutive, and sequential. The tandemcycloaddition of nitroalkenes is a very complex process consisting of a number of elementary reactions. The examples of the tandem cycloadditions of nitroalkenes reviewed here demonstrate a well‐developed strategy that can and has been applied for syntheses of many natural and unnatural compounds.