A short and efficient synthesis of pyrazino-fused tetraazafulvalenes

摘要

The tetraazafulvalenes 1 can be easily transformed into pyrazino fused derivatives of type 3 and 4 via cyclization of both vicinal secondary arylamino functions with chloroacetaldehyde acetals. Similarly, in the course of a complex reaction acetals of propionaldehyde, phenylacetaldehyde, propiophenone and deoxybenzoin lead to deeply blue colored ring fused products of type 7. This easily feasible annulation reaction is applicable to other heterocycles which contain a comparable bis-amidine substructure as examplified for 2,3-bis[arylamino]quinoxalines to give the heterocycles 15-17. [References: 7]