Chemistry of the phenoxathiins and isosterically related heterocycles. XXXII . The synthesis of 2‐azathianthrene and selected analogs

Abstract

Abstract The synthesis of 2‐azathianthrene ([1,4]benzodithiino[2,3‐c]pyridine), the only remaining monoazathianthrene yet to be reported, is described. Attempts at the direct condensation of disubstituted pyridines with the dianion of 1,2‐dimercaptobenzene were generally unsuccessful requiring that the alternative condensation of the dianion with disubstituted pyridine 1‐oxides be employed. The title compound was characterized by physical means including 13 C‐nmr spectroscopy. One analog, 4‐nitro‐2‐azathianthrene was also studied by X‐ray crystallographic means; the molecule crystallized with two molecules in the asymmetric unit P2 1 /n, a = 20.712(3), b = 7.8109(13), c = 13.720(2)Å, β = 107.880(11)°, Z = 8, the data refined to a final R = 0.051 for 3061 reflections. Dihedral angles between the planes of the phenyl rings were 135.00(13) and 132.52(13)° for the two independent molecules contained in the crystal. Close nonbonded S ⃛O intramolecular contacts were observed in both molecules between the sulfur and nitro‐group oxygens. Both nitro groups are twisted out of the plane of the pyridine ring and are oriented at angles of 28.75 and 38.82° respectively.