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Multigram Synthesis of Trioxanes Enabled by a Supercritical CO2 Integrated Flow Process
Organic Process Research & Development ( IF 3.1 ) Pub Date : 2021-06-25 , DOI: 10.1021/acs.oprd.1c00111
Lingqiao Wu 1 , Bruna L. Abreu 1 , Alexander J. Blake 1 , Laurence J. Taylor 1 , William Lewis 1 , Stephen P. Argent 1 , Martyn Poliakoff 1 , Hamza Boufroura 1 , Michael W. George 1
Affiliation  

Photochemical synthesis of highly reactive hydroperoxides and their conversion into useful products, such as 1,2,4-trioxanes, are of wide interest for synthetic organic chemistry and pharmaceutical manufacturing particularly because of their relevance as potential antimalarial and anticancer treatment drugs, for example, Artemisinin. One class of antimalarial drugs is based on 1,2,4-trioxane scaffolds although production of such compounds on a gram scale is challenging due to their instability in oxidizable solvents. Furthermore, current methods employ either solid oxidants, which make continuous processing problematic, or molecular oxygen, requiring long reaction times of up to 48 h. Here, we report a new multigram continuous approach using a custom-built high-pressure sapphire photoreactor to synthesize trioxanes via the dearomatization of para-substituted phenols by photogenerated singlet oxygen in supercritical CO2. CO2 also facilitates mixing with O2 and has lower viscosity, thereby improving penetration into the pores of the solid acid catalyst used for the formation of trioxanes. We show the capabilities of a 5.2 mL reactor to scale up the reaction to 67 g/day. This synthetic approach provides a platform to rapidly access high-value compounds under flow conditions, with high atom efficiencies, excellent yields, short reaction times, and without the need for isolation of hazardous intermediates.

中文翻译:

通过超临界 CO2 集成流动工艺实现三恶烷的多克合成

高活性氢过氧化物的光化学合成及其转化为有用的产品,如 1,2,4-三恶烷,在合成有机化学和药物制造中具有广泛的兴趣,特别是因为它们与潜在的抗疟疾和抗癌治疗药物相关,例如,青蒿素。一类抗疟药物基于 1,2,4-三恶烷支架,但由于它们在可氧化溶剂中的不稳定性,以克规模生产此类化合物具有挑战性。此外,目前的方法使用固体氧化剂,这使得连续加工成为问题,或者使用分子氧,需要长达 48 小时的长反应时间。在这里,我们报告了一种新的多克连续方法,使用定制的高压蓝宝石光反应器通过脱芳构化合成三恶烷光生单线态氧在超临界 CO 2 中对位取代的苯酚。CO 2还促进与O 2 的混合并且具有较低的粘度,从而提高对用于形成三恶烷的固体酸催化剂的孔的渗透。我们展示了 5.2 mL 反应器将反应放大到 67 g/天的能力。这种合成方法提供了一个平台,可以在流动条件下快速获取高价值化合物,原子效率高、产率高、反应时间短,并且无需分离危险中间体。
更新日期:2021-08-20
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