Solvent- and chromatography-free amination of pi-deficient nitrogen heterocycles under microwave irradiation. A fast, efficient and green route to 9-aminoacridines, 4-aminoquinolines and 4-aminoquinazolines and its application to the synthesis of the drugs amsacrine and bistacrine

Focused microwave irradiation of equimolecular mixtures of 9-chloroacridines, 4-chloroquinolines and 4-chloroquinazolines with amines in the presence of 2 equiv of phenol allows the general, fast and high-yielding synthesis of aminated heterocycles, with a very broad scope in terms of amine structure (aromatic, linear primary aliphatic, α-branched primary aliphatic, secondary aliphatic and diamines). Workup consisted of a simple washing with water and purification could be achieved by crystallization, avoiding the use of organic solvents in extraction and chromatographic purification steps. This protocol provides a solution to the long-standing synthetic problem of achieving a practical and efficient method for the amination of pi-deficient nitrogen heterocycles for medicinal chemistry applications.