Bishir Cody, Hubbard Abbey, Mei Liangyong
Department of Chemistry and Biochemistry, University of North Florida, Jacksonville, Florida 32224, United States.
ACS Omega. 2025 Mar 7;10(10):10713-10723. doi: 10.1021/acsomega.5c00416. eCollection 2025 Mar 18.
A visible-light-induced Rose Bengal- or [Ru(bpy)]-catalyzed radical [4 + 2] cycloaddition of redox-active indole -hydroxyphthalimide esters with electron-deficient alkenes has been developed. This base-free protocol provides a facile and powerful route for the synthesis of functionalized and biologically significant tetrahydrocarbazoles under mild conditions. On one hand, when an organic photocatalyst-Rose Bengal was employed under green light, the desired tetrahydrocarbazoles were obtained in up to 82% yield. On the other hand, the reaction yield increased to up to 93% in the presence of [Ru(bpy)Cl]·6HO under blue light. The success of the gram-scale and transformation experiments, as well as the photopromoted radical [5 + 2] cycloaddition further highlight the practicality and robustness of this protocol. Mechanistic studies also support the generation of a crucial alkyl radical intermediate.
已开发出一种可见光诱导的玫瑰红或[Ru(bpy)]催化的氧化还原活性吲哚-羟基邻苯二甲酰亚胺酯与缺电子烯烃的自由基[4 + 2]环加成反应。这种无碱方法为在温和条件下合成功能化且具有生物学意义的四氢咔唑提供了一种简便而强大的途径。一方面，当在绿光下使用有机光催化剂玫瑰红时，所需的四氢咔唑以高达82%的产率获得。另一方面，在蓝光下[Ru(bpy)Cl]·6H₂O存在下，反应产率提高到高达93%。克级规模反应和转化实验的成功以及光促进的自由基[5 + 2]环加成反应进一步突出了该方法的实用性和稳健性。机理研究也支持关键烷基自由基中间体的生成。
