Photochemical Flow Synthesis of Trisubstituted Oxazoles Enabled by High-Power UV–B LED Modules

The use of a newly developed UV-B LED module for the
continuous
flow synthesis of a variety of trisubstituted oxazole products from
readily available isoxazoles is reported. Crucially, this work demonstrates
for the first time that these UV-LED modules (up to 40 W electrical
power) are effective replacements of classical medium-pressure Hg-lamps
by providing monochromatic light (centered at 308 nm) which facilitates
the highlighted photochemical process. The desired oxazole products
are afforded in high yields, and the applicability toward synthesizing
analogs of the anti-inflammatory drug oxaprozin at multigram scale
is reported. The availability of such high-power UV-LED modules not
only circumvents the use of inefficient metal vapor lamps but also
highlights new opportunities for light-driven processes in general.

本文报道了采用新型开发的UV-B LED模块（UV-B LED module），以易得的异噁唑为原料，通过连续流合成工艺制备多种三取代噁唑类产物的研究。尤为关键的是，本研究首次证实，电功率高达40 W的该UV-LED模块可作为传统中压汞灯（medium-pressure Hg-lamps）的高效替代方案：其发射的中心波长为308 nm的单色光，可有效促进本文所重点研究的光化学反应过程。目标噁唑类产物均以优异收率获得；本文同时报道了该工艺在多克级规模合成抗炎药奥沙普嗪（oxaprozin）类似物方面的应用可行性。此类大功率UV-LED模块的问世，不仅规避了低效金属蒸气灯的使用，同时也为各类光驱动化学反应开辟了全新的研究机遇。