Regioselective synthesis of pyrimido[5,4-c][2,1]benzothiazines by reactions of β-chloroaldehydes with N-C-N binucleophiles
(Chemical Equation Presented) The method of pyrimidine ring fusion at the [c] side of benzothiazines based on the reaction of their chloroaldehyde derivatives with amidines is described. Formation of the structural isomers of reaction products was investigated, and regioselectivity of heterocyclization reactions was shown. A number of novel pyrimidobenzothiazines were synthesized.