New tetracyclic ring systems. Synthesis of 1H-oxazolo[5,4,3-kl]phenothiazines and [1,4]oxazino[2,3,4-kl]phenothiazines

1-Hydroxyphenothiazine was converted to 1H-oxazolo5,4,3-kl]phenothiazin-1-one, 1H-oxazolo5,4,3-kl]-phenothiazine-1-thione,1,4]oxazino2,3,4-kl]phenothiazin-1(2H)one and 1,4]oxazino2,3,4-kl]phenothiazine-1,2-dione. Also prepared from 1-hydroxyphenothiazine were the N-chloroacetyl derivative, the O-chloroacetyl derivative, the N,O-di(chloroacetyl) derivative and the sulfoxide.