Microwave-assisted traceless synthesis of benzimidazolones

We have developed a microwave-assisted traceless rapid synthesis of benzimidazolones on polymeric supports. The key step in our approach involves an arylation of benzylammonia followed by treatment with N-chlorosulfonyl isocyanate and by subsequent hydrolysis to yield the corresponding primary ureas. Intramolecular cyclization of the resin-bound primary ureas under Pd-catalyzed condition followed by cleavage with TFA–H2O provided the desired benzimidazolones with excellent yields and high purities. Except for step 4, the other reactions involved were performed completely within a few minutes under microwave exposure.