Iron-Catalyzed Cycloisomerization and C-C Bond Activation to Access Non-canonical Tricyclic Cyclobutanes.

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 [(Ph 3 P) 2 Fe(CO)(NO)]BF 4 as catalyst in good to excellent yields with high levels of stereocontrol.