Acta Chimica Sinica ›› 2021, Vol. 79 ›› Issue (6): 747-750.DOI: 10.6023/A21030096 Previous Articles     Next Articles

Communication

光化学条件下(β-重氮-α,α-二氟乙基)膦酸酯与羧酸的酯化反应

刘江a, 徐敬成a, Romana Pajkertb, 梅海波a, Gerd-Volker Röschenthalerb,*(), 韩建林a,*()   

  1. a 江苏省林业资源高效加工利用协调创新中心 化学工程学院 南京林业大学 南京 210037
    b 生命科学与化学学院 不来梅雅各布大学 不来梅 28759
  • 投稿日期:2021-03-17 发布日期:2021-04-26
  • 通讯作者: Gerd-Volker R?schenthaler, 韩建林
  • 基金资助:
    中国国家自然科学基金(21761132021); 德国科学基金(Grant RO 362/74-1)

Esterification of Carboxylic Acids with (β-Diazo-α,α-difluoroethyl)phosphonates under Photochemical Conditions

Jiang Liua, Jingcheng Xua, Romana Pajkertb, Haibo Meia, Gerd-Volker Röschenthalerb(), Jianlin Hana()   

  1. a Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
    b Department of Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Campus Ring 1, 28759 Bremen, Germany
  • Received:2021-03-17 Published:2021-04-26
  • Contact: Gerd-Volker R?schenthaler, Jianlin Han
  • Supported by:
    National Natural Science Foundation of China(21761132021); German Research Foundation(Grant RO 362/74-1)

Fluoroalkyl-substituted diazo compounds belong to one of the most powerful tools in organic synthetic chemistry and their transformations have attracted numerous attention. Since the reagent, trifluorodiazoethane, was discovered in 1943, it has attracted many research interests in organic synthesis. On the contrary, the similar difluorodiazoethane (CF2HCHN2), which just changes CF3 group to CF2H group, however, leads to significant changes on their chemical properties, in particular the stability. Until now, the studies on difluorinated diazo compounds remain less explored. Therefore, the related chemistry on difluorodiazoethane emerges as a hot research topic, and the inventory of methods for the preparation and application of new diazo compounds is continuously supplemented. In this communication, a visible-light- promoted esterification reaction of carboxylic acids with in situ generated (β-diazo-α,α-difluoroethyl)phosphonates via O-H insertion has been achieved under mild conditions, which afforded α,α-difluoromethyl phosphonates (DFMPs)-containing esters with good chemical yields. Several carboxylic acids and amines featuring various functional groups are well compatible in the reaction under photochemical conditions. A control experiment with the addition of D2O has been performed to verify the proton-transfer process involved in this reaction, and a possible mechanism containing in situ generation of diazo intermediate and protonation is provided. This reaction is operationally simple and shows good functional group compatibility providing an efficient and sustainable strategy for the assembly of α,α-difluorinated phosphonate derivatives. A typical procedure for this visible-light- promoted reaction between (β-diazo-α,α-difluoroethyl)phosphonates and carboxylic acids is presented as follows: into a vail were taken amine 1 (0.2 mmol), carboxylic acid 2 (0.1 mmol), t-BuONO (0.24 mmol) and CHCl3 (3 mL). The mixture was heated to 60 ℃ and stirred in the presence of 4.5 W blue LEDs for 4 h. Then, solvent was removed in vacuum. Product 3was purified by TLC plate of 20 cm×20 cm using petroleum ether/ethyl acetate (4∶1,V/V) as eluent.

Key words: difluorodiazoethane, (β-diazo-α,α-difluoroethyl)phosphonates, visible-light-initiation, O-H insertion, masked carbene