A diversity-oriented synthesis of cyclopenta[b]pyrroles and related compounds through a calcium(ii)/copper(ii) catalytic sequence†
We report herein a sequential bicatalytic route to provide a versatile access to a wide range of synthetically useful nitrogen-containing heterocycles in a single pot from furan and aniline derivatives. This transformation relies on an aza-Piancatelli/hydroamination sequence promoted by common calcium(II) and copper(II) salts. Depending on the substitution pattern of the precursors as well as the solvent employed, this method enables the preparation of biologically relevant molecules such as cyclopenta[b]pyrroles, pyrrolo[1,2-a]quinoxalines and also a novel class of cyclopenta[b]pyrrolines. Moreover, the first atropodiastereoselective synthesis of N-aryl cyclopenta[b]pyrroles is described.