Intramolecular Dearomative [2 + 2] Cycloaddition of (Hetero)arenes via Energy Transfer Catalysis: Exploration of
Kaiao Xu1, Xueying Wang1, Yaqian Liu1
1College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, P. R. China.
Abstract:
Dearomative [2 + 2] cycloadditions offer a powerful route for converting planar arenes into complex three-dimensional (3D) scaffolds prevalent in bioactive molecules. Herein, we report an intramolecular dearomative [2 + 2] cycloaddition of N-acryloyl-N-substituted α/β-naphthamides and benzoheterocycles, driven by visible-light energy transfer catalysis. This strategy effectively overcomes the high energetic barrier of dearomatization, facilitating the construction of synthetically valuable, strained fused-ring systems with divergent 3D architectures. The reaction exhibits a broad substrate scope and excellent functional group tolerance. Mechanistic investigations uncover a retro-cycloaddition pathway that divergently generates two structurally distinct fused-ring skeletons: direct ring-closure and cross ring-closure products, with the former predominating initially. This work not only provides a novel method for 3D skeleton editing but also highlights the potential of energy transfer catalysis in constructing complex molecular architectures.
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Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.


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