Pomeranz‐Fritsch Reaction

Abstract The synthesis of isoquinolines via an acid‐promoted electrophilic cyclization of benzalaminoacetals prepared from aromatic aldehydes and aminoacetals is generally referred to as the Pomeranz–Fritsch reaction. This reaction can directly give isoquinoline derivatives and is generally favored by electron‐donating substituents on the benzalaminoacetal. Various feasible acid promoters for this reaction have been recommended. This reaction gives low yields of isoquinolines, probably because of the steric and electronic effect and the partial deactivation of the phenyl ring. This reaction has been extensively modified by different methods and extended to prepare other types of aromatic heterocycles, such as thieno and thieno pyridines by intromolecular cyclization to thiophene ring. This reaction has been applied for the preparation of isoquinoline derivatives.