A cationic Fe−NO complex catalyses the cycloisomerization of cyclopropyl enyne to fused non-canonical cyclobutanes with up to four consecutive stereocenters with exclusive diastereoselectivity. Only Ag(+I) was found to show comparable activity, albeit significantly lower reactivity.
Cycloisomerizations are powerful skeletal rearrangements that allow the construction of complex molecular architectures in an atom-economic way. We present here an unusual type of cyclopropyl enyne cycloisomerization that couples the process of a cycloisomerization with the activation of a C−C bond in cyclopropanes. A set of substituted non-canonical tricyclic cyclobutanes were synthesized under mild conditions using [(Ph3P)2Fe(CO)(NO)]BF4 as catalyst in good to excellent yields with high levels of stereocontrol.Zum Volltext