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

Abstract

Abstract A series of 8‐substituted and 7,8‐disubstituted‐4‐oxo‐3‐(4 H ‐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‐(4 H ‐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.