Acta Chim. Sinica ›› 2018, Vol. 76 ›› Issue (12): 956-961.DOI: 10.6023/A18080333 Previous Articles     Next Articles

Special Issue: 有机氟化学



何世江, 皮静静, 李炎, 陆熹, 傅尧   

  1. 中国科学技术大学化学系 合肥 230026
  • 投稿日期:2018-08-13 发布日期:2018-11-09
  • 通讯作者: 陆熹,;傅尧,;
  • 基金资助:


Nickel-Catalyzed Suzuki-Type Cross Coupling of Fluorinated Alkenyl Boronates with Alkyl Halides

He Shijiang, Pi Jingjing, Li Yan, Lu Xi, Fu Yao   

  1. Department of Chemistry, University of Science and Technology of China, Hefei 230026
  • Received:2018-08-13 Published:2018-11-09
  • Contact: 10.6023/A18080333;
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 21572212, 21732006, 21702200, 51821006), and Major Program of Development Foundation of Hefei Center for Physical Science and Technology (2017FXZY001).

The incorporation of fluorine atoms or fluorine-containing fragments to specifical sites of organic compounds would result in unique diversifications in biological or physical properties, such as, significantly regulate the lipid solubility or metabolic stability, and promote specific binding ability to biological targets of target compounds. Monofluoroalkenes are ideal amide bond mimics, and have been widely used in the research field of pharmaceutical chemistry and drug discovery. Previously, we reported the nickel-catalyzed reductive cross coupling of gem-difluoroalkenes with unactivated secondary alkyl iodides and tertiary alkyl bromides. However, only medium yield can be obtained with primary alkyl halides, which might be caused by the lower stability and nucleophilic activity of these substrates. Herein, we report the nickel-catalyzed Suzuki-type cross coupling of fluorinated alkenyl boronates with alkyl halides for the synthesis of primary alkyl group substituted monofluoroalkenes. By using NiBr2(diglyme) (10 mol%) and 4,4'-di-tert-butyl-2,2'-bipyridine (15 mol%) as catalytic systems, Na2CO3 (2 equiv.) as base, N,N-dimethylacetamide as solvent, we achieved the cross coupling of a variety of fluorinated alkenyl boronates with primary alkyl iodides (e.g., 5), bromides (e.g., 9) and relatively inert secondary alkyl bromide (20). Under the mild reaction conditions, this reaction performed smoothly with good isolated yields and well functional group toleration. Many synthetically useful functional groups could survive during the transformation, such as, ether (6, 7), trifluoromethyl (8), cyano (10), ester (11), and even unprotected alcohol hydroxyl group (13). In addition, heterocycles such as tetrahydrofuran (14), phthalimide (15), dioxane (16), indole (17), pyridine (27) and quinoline (35) also posed no problem for this reaction. It should be pointed out that, this reaction is applicable not only to non-activated alkyl halides, but also to the conversion of activated allyl bromides (18, 19). For the fluorinated alkenyl boronates, this reaction also exhibited good functional group compatibility and wide substrate scope, and conducted successfully with both electron-rich (e.g., 4, 24), electron-neutral (e.g., 21), or electron-deficient (e.g., 27, 31) aromatic rings. Finally, the toleration of aryl sulfonate (30) provided further opportunities for subsequent modification through transition-metal-catalyzed cross coupling reactions. Radical clock experiment with (Z)-8-iodooct-3-ene (36) provided a mixture of linear product (37a) and ring-cyclized product (37b). (Bromomethyl)cyclopropane (38) was also subjected to the standard reaction conditions, only ring-opening product (39a) was obtained. In addition, this reaction was significantly inhibited with the addition of TEMPO (2,2,6,6-tetramethylpiperidinooxy). These results indicated a radical-type reaction mechanism for the cross coupling of fluorinated alkenyl boronates with alkyl halides. Further efforts would be devoted to develop one-pot synthesis of monofluoroalkenes through in-situ borylation of gem-difluoroalkenes and subsequent Suzuki-type cross coupling with alkyl halides.

Key words: nickel, fluorinated alkenyl boronate, alkyl halides, Suzuki-type cross-coupling, fluorinated olefin