FeCl3-Catalyzed Intermolecular Formal [8π+2σ] Cycloaddition of Azaheptafulvene with Bicyclo[1.1.0]butanes for the Synthesis of Cycloheptatriene-Fused 2-Azabicyclo[3.1.1]heptanes

Higher-order cycloadditions are a simple and effective strategy for constructing significant medium-sized architectures. Azaheptafulvenes reacting with readily accessible bicyclo[1.1.0]butanes (BCBs) through FeCl3-promoted intermolecular formal [8π+2σ] cycloaddition reactions to access cycloheptatriene-fused 2-azabicyclo[3.1.1]heptanes 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.