A Concise Method for Constructing Pyrrolo[1,2-a]quinoxaline Derivatives via Pictet–Spengler Type Cyclization

A simple and efficient method for concise synthesis of pyrido[3,2-e]pyrrolo[1,2-a]pyrazine deriva­tives based on Pictet–Spengler type cyclization reaction has been successfully developed. This procedure tolerates different types of aldehydes and ketones as starting materials in the presence of trifluoroacetic acid to provide the desired heterocyclic products with medium to excellent yields. The heterocycle containing bromine could be further used as a building block to synthesize more complex compounds. This strategy is characterized by simple operation and environmental friendliness and is a reliable tool for synthesizing bioactive substances.