The Synthetic Potential and Chemical Aspects of the Gewald Reaction: Application in the Preparation of 2-Aminothiophenes and Related Heterocycles

Several compounds that contain the 2-aminothiophene structural motif have been found to be promising pharmacological agents, such as the antipsychotic drug olanzapine, which has already been commercialised. There are many approaches to the synthesis of 2-aminothiophenes; however, the Gewald reaction is considered to be the simplest and most convergent method for generating these heterocycles. The reaction is reviewed from its original development to the most recent advances in terms of substrate scope, reactivity, reaction conditions, and synthetic applications.