Acta Chimica Sinica ›› 2023, Vol. 81 ›› Issue (9): 1101-1107.DOI: 10.6023/A23040188 Previous Articles     Next Articles

Special Issue: 庆祝《化学学报》创刊90周年合辑

Communication

Brønsted酸催化炔酰胺分子内氢烷氧化/Claisen重排反应

翟彤仪a, 葛畅a, 钱鹏程b,*(), 周波a, 叶龙武a,c,*()   

  1. a 厦门大学 化学化工学院 厦门 361005
    b 温州大学 化学与材料工程学院 温州 325035
    c 中国科学院上海有机化学研究所金属有机化学国家重点实验室 上海 200032
  • 投稿日期:2023-04-30 发布日期:2023-06-13
  • 作者简介:
    庆祝《化学学报》创刊90周年.
  • 基金资助:
    国家自然科学基金(22125108); 国家自然科学基金(22121001); 厦门大学校长基金(20720210002); 及国家基础科学人才培养基金(J1310024)

Brønsted Acid-Catalyzed Intramolecular Hydroalkoxylation/Claisen Rearrangement of Ynamides

Tongyi Zhaia, Chang Gea, Pengcheng Qianb(), Bo Zhoua, Longwu Yea,c()   

  1. a College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005
    b College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325035
    c State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032
  • Received:2023-04-30 Published:2023-06-13
  • Contact: *E-mail: qpc@wzu.edu.cn; longwuye@xmu.edu.cn; Tel.: 0592-2185833
  • About author:
    Dedicated to the 90th anniversary of Acta Chimica Sinica.
  • Supported by:
    The National Natural Science Foundation of China(22125108); The National Natural Science Foundation of China(22121001); The President Research Funds from Xiamen University(20720210002); The National Found for Fostering Talents of Basic Science (NFFTBS(J1310024)

A Brønsted acid-catalyzed intramolecular hydroalkoxylation/Claisen rearrangement of ynamides for the synthesis of eight-membered lactams is presented. Firstly, the keteniminium intermediate was generated from the activation of ynamide by Brønsted acid, which could interact with intramolecular hydroxy group through hydrogen bonding and ion pairing effects. Then, the tandem hydroalkoxylation/Claisen rearrangement took place and produced eight-membered lactams. Meanwhile, preliminary studies were conducted into the chiral Brønsted acid-catalyzed kinetic resolution, and several chiral eight-membered lactams were successfully synthesized. Other notable features of this metal-free method include the simple procedure, mild reaction conditions and good functional group compatibility. This research provides a practical method for the synthesis of biologically important eight-membered lactam skeletons. Accordingly, MsOH (5 mol%, 0.005 mmol, 0.32 μL) was added to the solution of ynamide (1 equiv., 0.1 mmol) in dry PhCl (4 mL) at room temperature. The reaction mixture was then stirred at 60 ℃ and the progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion, the reaction was quenched with Et3N (0.005 mmol, 0.7 μL), concentrated and purified by chromatography on silica gel (eluent: petroleum ether/ethyl acetate, VV=5∶1), to afford the desired eight-membered lactam. Under this condition, a series of ynamides with different substituents worked smoothly to provide the corresponding eight-membered lactams efficiently. Furthermore, chiral Brønsted acid (10 mol%, 0.005 mmol, 3.5 mg) and H2O (0.05 mmol, 0.9 μL) were added to the solution of ynamide (1 equiv., 0.05 mmol) in PhCl (2 mL) at –20 ℃ and the progress of the reaction was monitored by TLC. Upon completion, the reaction was quenched with Et3N (0.005 mmol, 0.75 μL), concentrated and purified by chromatography on silica gel (eluent: petroleum ether/ethyl acetate, VV=5∶1), to afford the chiral eight-membered lactam and chiral substrate. Also, a plausible mechanism involving the hydrogen bonding and ion pairing effects is proposed based on experimental results.

Key words: ynamide, Brønsted acid catalysis, Claisen rearrangement, medium-sized lactam, kinetic resolution