Microwave-Assisted Rapid Synthesis of Benzimidazolones

Significance

Benzimidazolones were prepared in several steps starting from Ameba resin 1 (commercially available) under microwave conditions. Thus, the reaction of resin 1 with NH₂OHHCl followed by reduction with LiAlH₄ gave amino resin 2. The resin-bound arylamines 3 were obtained via the reaction of 2 with 1-chloro-2-fluorobenzene and subsequently transformed into the polymer-supported ureas 4 using CSI in THF. Cyclization of resin 4 using Pd(OAc)₂ and XantPhos followed by N-alkylation with alkyl halide to afford the resin-supported benzimidazolone 6. After TFA-mediated cleavage from the solid support, the benzimidazolones 7a-h were obtained in 87-96% yield with 85-96% purities.