Organic Chemistry: Current Research
Open Access
ISSN: 2161-0401
ISSN: 2161-0401
Xiaoqiang Hu
Ruhr-University Bochum, Germany
Posters & Accepted Abstracts: Organic Chem Curr Res
The C–N bond is one of the most prevalent bonds in biological and chemical compounds. Selective transformations of C–N bonds are of substantial interest for the late-stage functionalization of complex molecules in the context of pharmaceutical research and material sciences. However, the cleavage of inert C–N bonds remains a challenging task for scientists due to their thermodynamic stability and relatively high bond dissociation energies (ca. 80 kcal/ mol). Tsuji-Trost allylations based on allyl amine electrophiles are comparably well investigated with the use of various strong nucleophiles, such as amines, carbonyl compounds, sulfinate salts, phosphonium ylides, and phosphinic acids, via η3-allyl–metal intermediates. We believed that the challenge of cleaving an C–N bond (ca. pKa Me2N–H = 40 vs pKa MeCOO–H = 4.76) might be overcome based on the mechanistic knowledge gained in related Ru-catalyzed C–H functionalizations. A facile insertion of ruthenium into aromatic C–H and allylic C–N bonds are the key steps in a [Ru(p-cymene)Cl2]2-catalyzed ortho-C–H allylation of benzoic acids. This protocol allows drawing on the large pool of allylic amines for state-of-the-art ortho-functionalizations of arenes, turning neutral amines into leaving groups. The reaction proceeds smoothly at only 60°C for a wide range of allylic amines, carboxamides, and sulfonamides in combination with various aromatic carboxylates. Concise syntheses of biologically active compounds provide further evidence of the great synthetic potential of this methodology.
Xiaoqiang Hu received his BS from the Wuhan Polytechnic University in 2011. Subsequently, he began his PhD studies under the supervision of Prof. Jia-Rong Chen and Wen-Jing Xiao at Central China Normal University. Then he has worked as a postdoctoral fellow with Professor Lukas J. Gooßen at Ruhr-Universität Bochum. His research interests are visible light induced N-centered radical cascade reaction and carboxylate-directed sp2 C–H functionalization.