[8+3]‐Cycloaddition Reactions of Heptafulvenes or Azaheptafulvenes with α‐Halohydroxamates

Abstract The base‐mediated higher‐order [8+3]‐cycloaddition reactions of heptafulvenes or azaheptafulvenes with α‐halohydroxamates have been achieved under mild and metal‐free conditions. These reactions do not only provide a direct route for the synthesis of highly functionalized cycloheptatriene‐fused piperidinones and piperazinones in moderate to excellent yields, but they also enrich the chemistry of heptafulvenes and azaheptafulvenes. Furthermore, gram‐scale reactions and further derivatizations demonstrated the synthetic potential of these cycloaddition reactions.