Divergent synthesis of medium-sized rings with controllable ring sizes represents a longstanding challenge in organic synthesis. Herein, we developed a transition-metal-catalyzed switchable divergent cycloaddition of para-quinone methides and vinylethylene carbonates by controlling the steric hindrance of substituent. Different from reported alkoxide-triggered annulations, this process undergoes a regiodivergent allylation of para-quinone methides followed by 1,6-addition reaction, providing a new route to selectively synthesize seven- to ten-membered nitrogen-containing heterocycles in high yields with excellent regioselectivities. This protocol features a broad substrate scope, wide functional group tolerance as well as operational simplicity. The reaction mechanism was investigated by conducting a series of control experiments as well as DFT calculations and the origins of the regioselectivities of the cycloaddition process were rationalized.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (Nos. 82173664 , 81803342 ), “ShuangChuang” Research Team of Jiangsu Province (No. 20182036). C. Z. acknowledges King Abdullah University of Science and Technology (KAUST) for support and the KAUST Supercomputing Laboratory for providing computational resources of the supercomputer Shaheen II.
- Divergent cycloaddition
- Medium-sized rings
- para-Quinone methides
- Vinylethylene carbonates
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