Domino synthesis of benzo[4,5]imidazo[1,2-a]imidazo[1,2-c]quinazolines or -pyrimidines via recyclable magnetic Cu-MOF-74 catalysis.

Abstract

An improved protocol for the synthesis of 1,2-disubstituted benzo[4,5]imidazo[1,2-a]imidazo[1,2-c]quinazoline or -pyrimidine derivatives has been developed via a recyclable magnetic Cu-MOF-74-catalyzed cascade coupling-cyclization reaction. Utilizing the accessible open copper sites within its crystalline pores, this recyclable nanomaterial effectively promotes the domino transformation of 2-(2-bromoaryl/vinyl)imidazoles with benzimidazolinones, affording the target polycyclic heterocycles in good to excellent yields. The protocol exhibits a broad substrate scope, smoothly accommodating various electron-donating and electron-withdrawing substituents on both the bromophenyl and imidazole rings. Owing to its superparamagnetic properties, the catalyst can be readily isolated using an external magnet and reused for at least five consecutive cycles with negligible loss of catalytic activity.

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