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Higher-order cycloadditions are a simple and effective strategy for constructing significant medium-sized architectures. Azaheptafulvenes reacting with readily accessible bicyclo1.1.0butanes (BCBs) through FeCl 3 -promoted intermolecular formal 8π+2σ cycloaddition reactions to access cycloheptatriene-fused 2-azabicyclo3.1.1heptanes have been developed. This new reaction tolerated a wide range of azaheptafulvenes and BCBs. Furthermore, the amplification experiment and synthetic transformations of the adducts, including modifications of marketed drugs, further highlighted their practicalities. Control experiments and DFT calculations suggest that the diastereoselective 8π+2σ product formation may involve a stepwise pathway.
Zhu et al. (2025) studied this question.