Synthesis of Aminofuran-Linked Benzimidazoles and Cyanopyrrole-Fused Benzimidazoles by Condition-Based Skeletal Divergence.

A condition-based skeletal divergent synthesis was explored to achieve skeletal diversity in two component condensation reaction. Cyanomethyl benzimidazole was reacted with α-bromoketone under thermal conditions to furnish 2-aminofuranyl-benzimidazoles, while the same reaction afforded 3-cyano-benzopyrrolo-imidazoles under microwave irradiation. Two nonequivalent nucleophilic centers on benzimidazole moiety were manipulated elegantly by different reaction conditions to achieve the skeletal diversity.

One pot three component reaction for the rapid synthesis of pyrrolo[1,2-a]benzimidazoles.

An efficient strategy for the synthesis of pyrrolo[1,2-a]-benzimidazole (PBI) linked to an ionic liquid (ILs) as a soluble support under microwave irradiation was explored. The key intermediate benzimidazoles were synthesized via N-acylation followed by cyclodehydration of IL-supported methyl-3-amino-4-(isobutylamino) benzoate. The synthesis of the IL-bound PBI was performed by one-pot three-component condensation under microwave dielectric heating, which involved a Knoevenagel condensation and a [4+1]-cycloaddition reaction. The reaction was monitored directly by means of (1)H NMR. All final products were obtained in good yield and high purity after precipitation.