Accelerating Effect Induced by the Structure of α-Amino Acid in the Copper-Catalyzed Coupling Reaction of Aryl Halides with α-Amino Acids. Synthesis of Benzolactam-V8

The coupling of optically pure α-amino acids with aryl halides produces enantiopure N-aryl-α-amino acids with retention of configuration under the catalysis of CuI. This reaction can complete at much lower temperature than typical Ullmann condensation even for electron-rich aryl halides, which indicates that an accelerating effect induced by the structure of the α-amino acid exists in this reaction. α-Amino acids with larger hydrophobic groups give higher coupling yields, while those with smaller hydrophobic groups only deliver lower yields and no coupling products were detected for those with hydrophilic groups. No racemization was observed in most cases of this coupling reaction. After some controlled experiments, a possible mechanism including the π-complex and the intramolecular substitution reaction is proposed. Based on this catalyzed reaction, a facile and stereoselective synthesis of benzolactam-V8, a new PKC activator, is achieved.