Direct synthesis of oxaspirolactones in batch, photoflow, and solvent-free conditions via visible-light photo- and heterogeneous Brønsted acid relay catalysis
Shinje Miñoza, Wei-Cheng Ke, Yin-Yin Yu, and Hsuan-Hung Liao* Department of Chemistry, National Sun Yat-sen University, Taiwan
The oxaspirolactone motif is often found in various biologically relevant natural products. Their synthesis, however, is tedious, requiring several protection-deprotection sequences or necessitates the use of precious metals and hazardous gas (i.e., carbon monoxide). 1 One of the most appealing approaches to construct the title compound is the photooxygenation of readily prepared hydroxyalkylfurans using singlet oxygen ( 1 O 2 ) and subsequent acid or base-mediated spirocyclization, which circumvents the aforementioned issues. 2 In this study, we report operationally simple protocols for the one-step preparation of oxaspirolactones in batch, photoflow, and solid-supported solvent-free conditions. Our methods offer salient features such as milder reaction conditions, use of an environmentally benign solvent (for batch and photoflow conditions), excellent yields, column chromatography-free, and amenability to gram-scale, among others. References 1. J. Am. Chem. Soc. 2016, 138 , 10693–10699
2. Org. Lett. 2005, 7 , 2357–2359; 3. Org. Lett. 2009, 11 , 4556–4559
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© The Author(s), 2023
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