Azo-substituted aryl ketones are fundamental building blocks which are widely utilized in the field of photochemical materials, biosensors, medicinal chemistry, and food additives. For the synthesis of these compounds, many methodologies have been established to make them via the coupling of diazonium salts with arenes or the oxidation of the corresponding azo-containing secondary alcohols. However, these methodologies suffered from tedious reaction steps and a relatively limited substrate scope.
However， the regio- and chemoselective C-H bond activation of organic molecules by transition metal catalysts provides an atom-economic access to the construction of carbon carbon or carbon-heteroatom bonds, which could further lead to simple and efficient synthetic strategies for the functionalization of organic compounds. Therefore, developing an efficient synthetic approach to the direct catalytic C-H acylation of azoarenes by employing easily available acylating agents becomes more desirable.
Researchers from Chengdu Institute of Biology of CAS cooperated with South China University of Technology have developed a Pd(II)-catalyzed cascade oxidation/sp2 C-H acylation of azoarenes with aryl methanes using TBHP as an oxidant. This protocol allows us to use simple and readily available aryl methanes as the in situ generated acyl sources and provides a convenient access to the synthesis of an ortho-acylazoarenes library. Further transformation of these azoarenes into other biologically active molecules is currently underway in our laboratory. This novel methodology was also applied to the synthesis of liver X receptor agonist with efficiency and high selectivity. The result was published in Organic Letters 2013, 15(21), 5444-5447.
This research got supports from the NSFC (Nos. 21072063 and 21272229) and West Light Foundation of CAS (No. Y3C1011100).