Acta Chimica Sinica ›› 2023, Vol. 81 ›› Issue (5): 431-434.DOI: 10.6023/A23030103 Previous Articles     Next Articles

Communication

金/铱接力催化炔基酰胺环化/不对称烯丙基苄基化串联反应

王瑞祥a, 赵庆如b, 顾庆b,*(), 游书力a,b,*()   

  1. a 华东师范大学 庄长恭研究所 上海 200062
    b 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:2023-03-30 发布日期:2023-05-08
  • 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(21821002); 国家自然科学基金(22031012); 国家自然科学基金(22071260)

Gold/Iridium Catalyzed Alkynylamide Cyclization/Asymmetric Allylic Benzylation Cascade Reaction

Wang Rui-Xianga, Zhao Qing-Rub, Gu Qingb(), You Shu-Lia,b()   

  1. a Chang-Kung Chuang Institute, East China Normal University, Shanghai 200062, China
    b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
  • Received:2023-03-30 Published:2023-05-08
  • Contact: *E-mail: qinggu@sioc.ac.cn; slyou@sioc.ac.cn
  • About author:
    Dedicated to the 90th anniversary of Acta Chimica Sinica.
    ††These authors contributed equally to this work.
  • Supported by:
    National Natural Science Foundation of China(21821002); National Natural Science Foundation of China(22031012); National Natural Science Foundation of China(22071260)

Asymmetric allylic substitution reactions involving benzyl nucleophilic reagents can rapidly construct chiral molecules containing benzyl fragments, which has attracted widespread attention from organic chemists. Formal asymmetric allylic benzylation reactions have been achieved by utilizing methylene oxazole as an equivalent of benzyl nucleophile. However, the development of highly efficient asymmetric allylic benzylation reactions remains a great challenge mainly due to the poor stability and synthetic difficulty of methylene oxazole. In this work, we have developed gold- and iridium- catalyzed alkynylamide cyclization/asymmetric allylic benzylation cascade reactions. In the presence of gold-carbene complex (Au1) and the combination of [Ir(cod)Cl]2 and (Sa)-Carreira ligand, a wide range of enantioenriched oxazole derivatives, bearing a benzylic stereogenic center, were obtained in 49%~87% yields with 98%~>99% ee. A general procedure is described as the following: To a dried Schlenk tube were added [Ir(cod)Cl]2 (5.4 mg, 0.008 mmol, 4 mol%), (Sa)-L1 (16.2 mg, 0.032 mmol, 16 mol%) and 1,2-dichloroethane (1 mL) under argon atmosphere. The mixture was stirred at room temperature for 15 minutes to give a chiral iridium complex solution. Under an argon atmosphere, alkynylamide (0.2 mmol, 1.0 equiv.), allyl alcohol (0.4 mmol, 2.0 equiv.), Au1 (0.02 mmol, 12.4 mg, 10 mol%), Fe(OTf)2 (0.2 mmol, 70.6 mg, 1.0 equiv.) and 3 Å molecular sieves (80.0 mg) were added to another dry Schlenk tube, and then the above-prepared iridium catalyst was added. The reaction mixture was stirred at 40 ℃ until the starting materials were consumed (monitored by thin layer chromatography, TLC). The mixture was quenched with water (5 mL), and extracted with dichloromethane (5 mL×3). The combined organic layers were dried over anhydrous Na2SO4, filtered, and then concentrated in vacuo to afford the crude product. The residue was purified by column chromatography (V(petroleum ether)/V(ethyl acetate)=15/1 or 10/1) to afford product 3.

Key words: asymmetric catalysis, allylic benzylation, alkynylamide cyclization, cascade reaction, gold, iridium