The valence isomerisation of homocubane derivatives

Transition metal catalyzed rearrangements of small ring organic molecules

“…Other molecules possessing cyclopropyl moieties have been shown to undergo similar reactions. The results of these rearrangements suggest a mechanism similar to those of bicyclopentane (75) and tricyclooctane (61). The factors which deter- mine the relative amounts of products and subsequent isomerization remain to be determined.…”

“…73 lr(D Interestingly, 74 rearranged to a product analogous to the rearrangement product of 61 when Vaska's compound (Ir-CI(CO)[P(C6H5)3]2) was employed as the catalyst. Possibly, the high stability of the iridium-phosphorus bond to dissociation prevents the substrate from chelating, which in turn prevents insertion of the olefin (61) or cyclopropane (74) into the metalcarbon bond. For this reason the substrates react as isolated cyclopropane bonds.…”

“…This may indicate a change in the rate-determining step. A possible explanation of this comes from Paquette's careful kinetic analysis of the rearrangement of Moore's hydrocarbon (61).113 He has demonstrated than an equilibrium between catalyst and substrate (80) precedes the rate-determining step. The kinetics correspond to the scheme shown below, where k2 is rate determining.…”