First Metal-Free Synthesis of Tetracyclic Pyrido and Pyrazino Thienopyrimidinone Molecules.

We report herein a new metal free synthetic pathway to generate tetracyclic compounds from 3-aminothieno[3,2-b]pyridine-2-carboxylate. To enlarge the molecular diversity, we studied the Suzuki coupling of 9-chloro-6H-pyrido[1,2-a]pyrido[2',3':4,5]thieno[3,2-d]pyrimidin-6-one and several boronic acids were easily introduced.