Acta Chim. Sinica ›› 2017, Vol. 75 ›› Issue (1): 110-114.DOI: 10.6023/A16080414 Previous Articles     Next Articles

Special Issue: 有机光化学



周泉泉, 刘丹, 肖文精, 陆良秋   

  1. 农药与化学生物学教育部重点实验室和化学学院 华中师范大学 武汉 430079
  • 投稿日期:2016-08-15 修回日期:2016-10-07 发布日期:2016-10-10
  • 通讯作者: 陆良秋,;Tel.:027-67862041;Fax:027-67862041
  • 基金资助:


Visible-Light Photoredox Catalytic α-Cyanation Reactions of Tertiary Amines

Zhou Quanquan, Liu Dan, Xiao Wenjing, Lu Liangqiu   

  1. Key Laboratory of Pesticide & Chemical Biology Ministry of Education and College of Chemistry, Central China Normal University, Wuhan 430079
  • Received:2016-08-15 Revised:2016-10-07 Published:2016-10-10
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 21232003, 21472057 and 21572074).

Visible-light photoredox catalysis, a novel and green catalytic strategy, has recently received increasing attention from chemists and been widely applied to organic synthesis in the past years. This catalytic strategy enables the generation of various reactive species under mild conditions without stoichiometric activation reagents and shows its significance for sustainable chemistry. α-Amino nitriles are highly versatile intermediates having extensive applications in organic synthesis and biological transformation. The oxidation of tertiary amines using stoichiometric oxidants followed by the nucleophilic addition reaction of the iminium intermediate by cyanide ion (CN-) represents a direct approach for their synthesis. However, the use of stoichiometric oxidants and the production of huge amounts of hazardous waste (i.e., CN-) is undesirable from environmental viewpoints. Here, we report a photoredox catalytic α-cyanation reaction of tertiary amines using cyanobenziodoxol as a stable and safe cyanide source. This protocol is favored for mild conditions, the avoidance of extra oxidant and highly toxic cyano anion, good functional tolerance as well as safe and simple operations. By doing so, a variety of α-amino nitriles are afforded in good to excellent yields. A sunlight-driven reaction and a gram-scale reaction further demonstrate the utility of this methodology. In addition, we also succeed to apply the same strategy to the decarboxylative cyanation of carboxylic acids, affording the nitriles in moderate yields. A possible mechanism was proposed on the basis of known literature and our previous reports. The representative procedure for the α-cyanation reaction of tertiary amines is as following:N-phenyl piperidine 1a (0.48 mmol), cyanobenziodoxol 2a (0.40 mmol), photocatalyst Ir[dF(CF3)PPy]2(dtbbpy)PF6 (0.008 mmol) and CsHCO3 (0.60 mmol) were dissolved in DCM (8 mL). Then, the resulting mixture was degassed via 'freeze-pump-thaw' procedure (3 times). After that, the solution was stirred at a distance of ca. 5 cm from a 7 W blue LEDs (450~460 nm) at room temperature for 16 h. Upon completion, the crude product was purified by flash chromatography on silica gel (petroleum ether/ethyl acetate 30:1~10:1) directly to give the desired product. The procedure for the decarboxylative cyanation of carboxylic acids is similar.

Key words: visible-light photoredox catalysis, cyanation, α-amino nitrile, tertiary amine, decarboxylative transformation