and cyclopentanones, respectively. During [3+2] cycloaddition reactions, the substituent on the alkene may eliminate to provide cyclopentenones from alkenes in one pot. (11) The scope of [4+3] cycloadditions is broad—the reaction may be used to form cycloheptenones, as well as bridged or fused polycyclic products. Reduction may be carried out in the presence of the 4π component (12) Synthetic applications [4+3] cycloadditions of pyrroles may be used to establish the bicyclic skeleton of tropane alkaloids. For instance, a synthesis of scopine uses the [4+3] cycloaddition of N-methoxycarbonylpyrrole and α,α,α',α'-tetrabromoacetone as a key step. Diastereoselective reduction with diisobutylaluminum hydride (DIBAL-H) followed by epoxidation with trifluoroperacetic acid affords the target. (13) References Organic reduction reactions