4H-dithieno[2,3-b:3',2'-e][1,4]thiazines--synthesis and electronic properties of a novel class of electron rich redox systems

Quantum chemical screening reveals that 4H-dithieno2,3-b:3',2'-e]1,4]thiazines possess the highest HOMO among four constitutional isomers, even 0.27 eV higher in energy than the well established 10H-phenothiazine. N-Substituted 4H-dithieno2,3-b:3',2'-e]1,4]thiazines are readily accessible by twofold Pd-catalyzed amination. According to cyclic voltammetry dithienothiazines are reversibly oxidized and can be considered as new donors for functional π-systems.