Metal-free oxidative acylation/cyclization of N-methacryloyl-2-phenylbenzoimidazole with aryl aldehydes: an easy access to benzimidazo[2,1-a]isoquinolin-6(5H)-ones.

A metal-free radical cyclization strategy has been developed for the synthesis of fused benzimidazo[2,1-a]isoquinolin-6(5H)-one derivatives from N-methacryloyl-2-arylbenzoimidazole and aryl aldehydes using 70% tert-butylhydroperoxide in water (TBHP). The reaction proceeds through a sequential acyl radical addition/cyclization strategy. This method is useful for the generation of biologically relevant tetracyclic scaffolds in a single-step process.