Synthesis of 1,3-Benzodiazepines through [5 + 2] Annulation of N-Aryl Amidines with Propargylic Esters

In this paper, an efficient synthesis of functionalized 1,3-benzodiazepines through an unprecedented [5 + 2] annulation of N-aryl amidines with propargylic esters is presented. The reactions proceed through Rh­(III)-catalyzed C­(sp2)−H alkenylation followed by annulation and deacetoxylation along with cascade C−H/N−H/C−O bond cleavage and C−C/C−N bond formation. Furthermore, the cytotoxicity of selected products against several human cancer cell lines was tested, which demonstrated their good potential for pharmaceutical applications.