An efficient synthesis of benzo[4.5]imidazo[2,1-b]quinazolin-12-ones and benzo[4,5]imidazo-[1,2-a]pyrido[2,3-d]pyrimidin-5-ones is reported from the reaction of 2-aminobenzimidazole with 2-haloaroyl chlorides. The reaction takes advantage of the 1,3-disposition of nucleophilic centers in the 2-aminoimidazole and the similar arrangement of electrophilic sites in the acid chloride to assemble the central six-membered ring. Initial treatment of 2-aminobenzimidazole (1.2 eq) with the acid chloride (1 eq) in the presence of NaHCO3 (2 eq) in DMF at –10 oC gives acylation at the saturated benzimidazole nitrogen. Subsequent heating to 75 oC, in the same reaction vessel, then completes the synthesis via an SNAr ring closure by the C2 amino group. The reaction has relatively broad scope, and gives 76-98% yields for the two-step sequence. The final products exist in a tautomeric equilibrium, which can be blocked by acylation at N6.

Benzo[4,5]imidazo[2,1-b]quinazolin-12-ones and benzo[4,5]imidazo[1,2-a]pyrido[2,3-d]-pyrimidine-5-ones by a sequential N-acylation-SNAr reaction

251st National Meeting (2016)

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