The synthesis of some 4H‐pyrimido[2,1‐b]benzothiazol‐4‐ones

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Abstract
A series of 8‐substituted and 7,8‐disubstituted‐4‐oxo‐3‐(4H‐pyrimido[2,1‐b]benzothiazole)carboxylic acids and esters including a 9‐aza analog were synthesized from substituted 2‐aminobenzothiazoles and diethyl ethoxymethylenemalonate. The 9‐aza analog, ethyl 8‐methoxy‐4‐oxo‐3‐(4H‐pyrido[3′,2′:4,5]thiazolo[3,2‐a]pyrimidine)carboxylate (56), represents the first preparation of this new heterocyclic ring. These compounds were examined for antiparasitic activity, however, no significant activity was detected.