Benzimidazole condensed ring systems. <b>4</b>. New approaches to the synthesis of substituted pyrimido[1,6‐<i>a</i>]‐benzimidazole‐1,3(2<i>H</i>,5<i>H</i>)‐diones

Abstract

Abstract The synthesis of some substituted 1,3‐dioxopyrimido[1,6‐ a ]benzimidazole‐4‐carbonitriles 6a,b and 4‐ethyl carboxylates 6c,d through condensation of 1 H ‐benzimidazole‐2‐acetonitriles 3a,b and ethyl 1 H ‐benzimidazole‐2‐acetates 3c,d , respectively, with ethoxycarbonyl isocyanate 4 are reported. The esters 6c,d were also obtained by condensing 3c , or d with chlorosulfonyl isocyanate 7. The alkylation of 5 and 6 with trimethyl or triethyl phosphate 9a , or b to obtain the N,N ‐dialkyl derivatives 10a‐e and 11 are also described. Representative compounds were tested against P‐388 lymphocytic leukemia in mice and for herbicidal and plant fungicidal activities but were inactive.