Iron-catalyzed [3 + 2] annulation of aminocyclopropanes with aldehydes: stereoselective synthesis of aminotetrahydrofurans.

The first method for the [3 + 2] annulation of donor-acceptor aminocyclopropanes with aldehydes is reported. The reaction is catalyzed by iron trichloride on alumina in yields up to 99% and with excellent cis selectivities (up to >20:1) and represents a stereoselective and atom economic access to valuable 2-aminotetrahydrofurans, which constitute the core of DNA and RNA.