The synthesis of novel dipyridazinothiazine ring systems

The synthesis of several dipyridazinothiazines have been accomplished by: (a) cyclization in concentrated hydrochloric acid solution of the appropriate intermediates; and (b) via the Smiles rearrangement in either basic or glacial acetic acid solution of the appropriate intermediates. The following ring systems have been prepared and characterized: 10 H ‐dipyridazino‐[4,3‐ b :4′,5′‐ e ]‐1,4‐thiazine, 5 H ‐dipyridazino[3,4‐ b :4′,5′‐ e ]‐1,4‐thiazine, 10 H ‐dipyridazino[4,5‐ b :‐4′,5′‐ e ]‐1,4‐thiazine, 5 H dipyridazino[5,4‐ b :4′,3′‐ e ]‐1,4‐thiazine, and 10 H ‐dipyridazino[3,4‐ b :‐3′,4′‐ e ]‐1,4‐thiazine.