Efficient continuous synthesis of 2-hydroxycarbazole and 4-hydroxycarbazole in a millimeter scale photoreactor  

作　　者：Zhixiang Li Zhirong Yang Chang Yao Bin Wu Gang Qian Xuezhi Duan Xinggui Zhou Jing Zhang 

机构地区：[1]State Key Laboratory of Chemical Engineering,East China University of Science and Technology,Shanghai 200237,China [2]School of Chemical Engineering,Zhengzhou University,Zhengzhou 450001,China

出　　处：《Chinese Chemical Letters》2024年第4期399-403,共5页中国化学快报（英文版）

基　　金：funded by the National Natural Science Foundation of China(Nos.21991103,21991104,22008074,22008072);Natural Science Foundation of Shanghai(No.20ZR1415700);China Postdoctoral Science Foundation(Nos.2020M671025,2019TQ0093)。

摘　　要：2-Hydroxycarbazole and 4-hydroxycarbazole are important chemicals with extensive applications in optoelectronic materials and pharmaceutical field.State of the art yield of 2-hydroxycarbazole is~30%and the reaction time is typically in hours or days.Herein,we developed a green route for the continuous and high-throughput synthesis of 2-hydroxycarbazole and 4-hydroxycarbazole via photochemical intramolecular cyclization of 3–hydroxy-2–chloro-diphenylamine using a self-designed millimeter scale photoreactor,which was designed based on sizing-up and numbering-up strategies for a decent liquid holdup(6.8 m L)and fabricated via femtosecond laser engraving technique.The photochemical synthesis was carried out continuously under the illumination of 365 nm UV-LED with dimethyl sulfoxide as solvent and potassium t-butoxide as catalyst.It was found that under optimized conditions a 2-hydroxycarbazole yield of 31.6%and a 4-hydroxycarbazole yield of 11.1%were obtained with a residence time of 1 min.Compared to semibatch operations,the reaction time was shortened by 1–2 orders of magnitude.As a result,a throughput of 11.3 g/day 2-hydroxycarbazole and 4.0 g/day 4-hydroxycarbazole can be achieved from the photoreactor.It was proposed that the short reaction time and high product yield are resulted from higher photon transfer rates and more uniform photon distribution provided by the millimeter scale photoreactor,which enhances the reaction rates and mitigates overreaction.

关 键 词：Millimeter scale reactor 2-Hydroxycarbazole PHOTOCHEMISTRY UV-LED Process intensification 

分 类 号：O626[理学—有机化学]