Syntheses of Heterocyclic Compounds involving Sulfur. I. Syntheses of 1, 3-Dihydro-2H-pyrimido [5, 6, 1-kl] phenothiazine, 1, 2-Dihydro-3H-pyrazino [3, 2, 1-kl] phenothiazine and 1, 2-Dihydroimidazo- [4, 5, 1-kl] phenothiazine

Reaction of 1-tosylaminomethylphenothiazine (VI) and methylene iodide gave 2-tosyl-1, 3-dihydro-2H-pyrimido [5, 6, 1-kl] phenothiazine (VII). 3-Tosyl-1, 2-dihydro-3H-pyrazino- [3, 2, 1-kl] phenothiazine (XIV) or 2-tosyl-1, 2-dihydroimidazo [4, 5, 1-kl] phenothiazine (XVIII) was synthesized from 1-tosylaminophenothiazine (XIII) and ethylene bromide or methylene iodide. Detosylation of VII, XIV, and XVIII gave 1, 3-dihydro-2H-pyrimido [5, 6, 1-kl] -phenothiazine (VIII), 1, 2-dihydro-3H-pyrazino [3, 2, 1-kl] phenothiazine (XII), and 1, 2-dihydroimidazo [4, 5, 1-kl] phenothiazine (XVII), respectively. In addition, syntheses of these new four-ringed nitrogen heterocycles were studied by other routes.