Light-Activated BF3·Et2O-Promoted Generation of Singlet Oxygen and Cascade Reaction of Unsaturated Amides

Hongli Chai; Xueqing Wang; Xingyu Ma; Xiang Zhen; Yuji Qin; Liang Qi; Zhaoqing Xu; Fuchong Li; Weiwei Zhu

doi:10.1021/acs.orglett.3c04172

Light-Activated BF₃·Et₂O-Promoted Generation of Singlet Oxygen and Cascade Reaction of Unsaturated Amides

Org Lett. 2024 Mar 8;26(9):1775-1779. doi: 10.1021/acs.orglett.3c04172. Epub 2024 Feb 26.

Authors

Hongli Chai^{1

2}, Xueqing Wang³, Xingyu Ma¹, Xiang Zhen², Yuji Qin¹, Liang Qi³, Zhaoqing Xu², Fuchong Li⁴, Weiwei Zhu^{1

5}

Affiliations

¹ School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, China.
² Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Science, Lanzhou University, Lanzhou 730000, China.
³ Department of Pharmacy, College of Life Sciences, China Jiliang University, Hangzhou 310018, China.
⁴ Lanzhou Chemical Research Center of PetroChina, Lanzhou, 730000, China.
⁵ National-Local Joint Engineering Laboratory of Druggability and New Drugs Evaluation, Guangdong Provincial Key Laboratory of New Drug Design and Evaluation, Guangdong Province Engineering Laboratoty for Druggability and New Drug Evaluation, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China.

PMID: 38408019
DOI: 10.1021/acs.orglett.3c04172

Abstract

Herein, BF₃·Et₂O-promoted O-insertion/spirocyclization/fluorination/ring-expansion of unsaturated amides to synthesis of spiro[benzo[b]-[1,4]dioxepine-3,5'-oxazole] skeletons in the presence of natural light and O₂ (³Σ_g^-) was reported. Air was the oxygen source of the ¹O₂-generation and O-insertion reaction under metal-free and mild conditions. BF₃·Et₂O played multiple roles, such as Lewis acid, activating reagent, and fluorine source in the reported cascade. A mechanism involving ¹O₂ generation/activation of double bond/O-insertion/spirocyclization/fluorination/ring expansion was supposed.