A theoretical study of thermal reactions of bicyclo[2.1.0]pent-2-ene

Origin of the Preference for the Orbital Symmetry Forbidden Stereochemistry of the 1,5-Sigmatropic Shift of Substituted Norcaradienes

“…The NBOs of forming and breaking bonds are 0.107 in 2 and 0.114 in 3 . These distances and NBOs are similar to those in the transition structure for the analogous 1,3-shifts of vinylcyclopropane 5a,b and bicyclo[3.2.0]hept-2-ene 5c. The forbidden [1i,5s] transition structure 3 is computed to be 0.9 kcal/mol more stable than the [1r,5s] by UB3LYP and 0.3 kcal/mol by CASSCF, but 0.5 kcal/mol less stable by CASPT2N//CASSCF calculations (Table ).…”

“…Dynamics should also favor the inversion pathway observed in the cycloheptatriene walk rearrangement. For the analogous vinylcyclopropane−cyclopentene rearrangement and the 1,3-shift of bicyclo[3.2.0]hept-2-ene, the potential energy surfaces alone can explain qualitatively the reaction stereochemistry . The walk rearrangement in bicyclo[2.1.0]pent-2-ene has been studied by Morokuma et al .…”

“…The walk rearrangement in bicyclo[2.1.0]pent-2-ene has been studied by Morokuma et al . 5d We report theoretical investigations which provide an explanation of the unexpected stereochemistry in the 1,5-shift of norcaradiene.…”

A Main‐Group Analogue of Housene: The Subtle Influence of the Inert‐Pair Effect in Group 15 Clusters

“…We considered several dynamic processes that may account for this fluxionality,13 and concluded the most likely mechanism was conceptually related to the “walk rearrangement” which has been extensively discussed for both housene and 1,2‐HP‐1,3‐P 2 (CH) 2 . Here, the bridgehead group migrates in a series of 1,3 sigmatropic shifts around the edge of the ring and C s ‐symmetric transition states lead to inversion of configuration at the bridgehead atom 14. 15 In the case of housene, the barrier to this 1,3 shift is rather large (31 kcal mol −1 ) and the transition state has strong biradical character with one unpaired electron on the CH 2 fragment, the other delocalized in the allyl unit of the C 4 ring 16.…”

Theoretical study of the pericyclic/pseudopericyclic character of the automerization of Perfluorotetramethyl (Dewar thiophene) exo-S-oxide

“…According to Skancke et al (UHF, CASSCF, Møller-Pleset calculations) this thermal walk rearrangement goes via inversion at the migrating center. 43 The rearrangement is likely a two-step process passing through a diradical intermediate. However, later, Jensen using a multiconfigurational self-consistent field (MCSCF) found that the Woodward-Hoffman allowed reaction is a concerted process with a C s symmetry transition structure.…”