Research of C-H activation has been conducted in worldwide because of its applicability that C-H bond can be exchanged with C-X bond (X= C, O, N, etc.). To activate specific C-H bond, transient directing group is needed for high regioselectivity and efficiency. Therefore, we found the reaction condition and efficient transient directing group to activate γ-C(sp3)-H bond of cyclohexylamine.
As a result, 3-bromosalicylaldehyde is the most effective transient directing group in promoting C-H arylation. This reaction progressed with substituted aryl iodides regardless of electronic properties and position of substituent. Both of Electron-rich and electron-deficient aryl iodides afforded the desired products with good yield. In addition, aryl iodides bearing substitutions at the ortho, meta and para position are also well tolerated. Furthermore, C-H arylation proceeded with aliphatic amine, cyclopentyl amine and cycloheptyl amine.
To demonstrate the utility of this reaction, further research is being carried out to obtain desired ketone product from substituted amine. Ketone is an important precursor in organic chemistry. Herein we have synthesized β- substituted ketone from γ-substituted amine compound. Substituted amine compound oxidized to imine using TPAP and NMO. Then imine compound converted to ketone after adding hydrochloric acid solution. To synthesize β- substituted ketone, 1,4-addition of enone using Gilman reagents is usually used. However, when Gilman reagents have electrophilic substituent such as carbonyl group, desirable ketone cannot be obtained. Through this reaction, diverse arylated ketone can be synthesized with any substituent regardless of its electronic properties.