Molecular orbital view of the stereochemical behavior in the interaction of bicyclo[2.1.0]pentane and unsaturated molecules

Energetically concerted reaction profile for the thermal conversion of cyclopropane to propene and for related cycloreactions

“…A Possible Rearrangement Pathway for Chloro Ketones 1 and 3 ROM product studies clearly indicate a stereoelectronic influence from the backside of the carbon-chlorine bond by the carboncarbon double bond at some stage prior to product formation. 13 Table I gives the results from quantum yield and multiplicity studies of chloro ketones including exo-2chloronorbornenone (9).6 Unfortunately, the endo isomer was not studied for comparison of stereoelec-(9) Synthetic details will be given in our full paper. All new compounds gave satisfactory elemental analyses.…”

Deazetation of a bicyclic azo compound: resolution of a stereochemical ambiguity and conformational analysis of a biradical

“…Another potential product, trans-bicyclo[4.2.0]octane (5), was synthesised by a route analogous to that used for the synthesis of trans-bicyclo[4.2.0]oct-3-ene and outlined in Scheme 2. It was absent from reactions of (1) (< 1% of the cisisomer), and control experiments, in which (5) was co-pyrolysed or co-photolysed with (1) under the standard conditions, showed that, if it had been formed, it would have survived.…”

“…Conformational Analysis of the Biradica1.-We have used Molecular Mechanics 2 5 to study the conformations of cyclooctanediyl(l1). Our model is very simple, using the parameters proposed by AllingerZ6 for carbon centred radicals and considering the two radical centres as independent, thus neglecting, among other factors, multiplicity.…”

The Theory of Pericyclic Reactions

“…Available experimental results confirm these predictions15' 531. The reactions of (21) and (22) are examples. It is very important to note that the regioselectivity of these two photodimerizations has been shown to be consistent with aconcerted [2s+2s] mechanism*"'!Alarge number of[2+2] photodimerizations known to yield products consistent with a concerted [2s+2s] mechanism can be found in recent reviews""!…”

“…Indeed, many years ago spectroscopists realized that the electronic transitions of molecules could be completely understood only on the basis of a theory which included configuration interaction as a key element[' 21. In The third development has been the realization that certain types of orbital interactions, other than frontier orbital interactions, can have some influence on the outcome of certain concerted reactions[231.…”