[8 + 3]‐cycloaddition reactions of heptafulvenes or azaheptafulvenes with a‐halohydroxamates

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