Synthesis of β-Aminoketones and Construction of Highly Substituted 4-Piperidones by Mannich Reaction Induced by Persistent Radical Cation Salts

Mannich reaction of imines and ketones induced by persistent radical cation salts was investigated, and a series of Mannich bases, beta-aminoketones, were synthesized. A novel cyclization to form the 4-piperidone skeleton was achieved in a tandem process. The reaction can be rationalized as a radical cation process supported by various evidence.