Doubly bridged biscyclopropenones, a new family of phanes

The first representatives, 10-12, of the new species of double-decked cyclopropenonophanes were synthesized by cycloaddition reactions of dichlorocarbene to alkynylenecyclopropenonophanes 7-9 followed by hydrolysis as well as in an alternative route involving hydride abstraction from dichlorotricycloalkadienes 16 and 17 to dichlorocyclopropenyliophanes and in situ hydrolysis of the latter. The X-ray analysis of [3.3]cyclopropenonophane 10 reveals a considerable tetragonalization of the bridgehead carbon atoms, indicating a significant deformation of the cyclopropenone moieties in the phane corset, According to ab initio calculations, the it orbitals of the cyclopropenones display transannular interactions of nearly the same scale as found in 7.