An efficient and simple aminobenzannulation reaction: Pyrrolidine as a trigger for the synthesis of 1-amino-acridines

A new aminobenzannulation methodology has been developed and applied successfully to the synthesis of 1-amino-acridines. The key and last step goes through an enamine intermediate that was detected in some cases. When pyrrolidine and powdered 4 angstrom molecular sieves were used, the enamine synthesis and the aminobenzannulation step took place subsequently, whereas for other secondary amines, neutral Al2O3 or PtCl2 catalysis was necessary.