A New Convenient Liquid- and Solid-Phase Synthesis of Quinoxalines from (E)-3-Diazenylbut-2-enes

3-{[(tert-Butoxy)carbonyl]diazenyl}but-2-enoates react in tetrahydrofuran at room temperature with aromatic 1,2-diamines to give 3-methylquinoxaline-2-carboxylates. These products were also obtained in solid-phase synthesis, by using polymer-bound 3-diazenylbut-2-enes.