Acta Chim. Sinica ›› 2017, Vol. 75 ›› Issue (1): 74-79.DOI: 10.6023/A16090492 Previous Articles     Next Articles

Special Issue: 有机光化学



吴自俊, 汪舰   

  1. 清华大学药学院 北京 100084
  • 投稿日期:2016-09-15 修回日期:2016-11-27 发布日期:2016-12-05
  • 通讯作者: 汪舰,;Tel:010-62772583
  • 基金资助:


Decarboxylative 1,6-Conjugate Addition of α-Keto Acids with para-Quinone Methides Enabled by Photoredox Catalysis

Wu Zijun, Wang Jian   

  1. School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084
  • Received:2016-09-15 Revised:2016-11-27 Published:2016-12-05
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 21672121).

α-Arylated and α,α'-diarylated carbonyls are an important class of building blocks and widely found in biologically active natural and unnatural molecules. The most popular approach to access α-arylated and α,α'-diarylated carbonyls involves transition-metal-catalyzed cross-coupling reactions and metal-free coupling reactions, which always request harsh conditions or high catalytic loading. 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. Inspired by the recent process of the visible light photocatalytic generation and exploration of α-keto acids as the precursor for acyl radical in decarboxylative cou-pling reactions and 1,4-Michael addition reactions, we found that, however, expand their utilization in more complex systems, such as 1,6-conjugate addition with electron deficient olefins, remains underdeveloped, particularly due to the difficult to design the appropriate substrate, and the harsh conditions often required for metal-catalyzed redox neutral decarboxylation. Here, we report a photoredox catalytic C-C bond formation reaction that enabled by visible-light. The versatility of this protocol has been portrayed by using a wide range of stable and easily accessible aromatic α-keto acids as well as p-QMs. This synthetic strategy also offers access to 24 kinds of different α-keto-α,α'-diarylated ketones in moderate to excellent yields under mild conditions. A representative procedure for the reaction is as follows:2-oxo-2-phenylacetic acid 1a (0.10 mmol), the p-QM (2,6-di-tert-butyl-4-(4-methoxybenzylidene) cyclohexa-2,5-dien-1-one) 2a (0.12 mmol), photocatalyst Ir[dF(CF3)PPy]2(dtbbpy)PF6 (0.001 mmol) and K2HPO4 (0.12 mmol) were dissolved in DCM (1 mL). Then, the resulting mixture was degassed and refilled with N2 via ‘freeze-pump-thaw’ procedure (3 times). After that, the solution was stirred at a distance of ca. 5 cm from a 36 W blue LEDs at room temperature for about 12 h with TLC monitoring. Upon completion of the reaction, the crude product was purified by flash chromatography on silica gel (hexane/ethyl acetate) to give the desired product 3.

Key words: visible light, photoredox catalysis, para-quinone methides, 1,6-conjugate addition, radical