Butadienylcyclopropane rearrangement

It was found that heating of the deuteriated bicyclodiene 111 at 110°C was accompanied by two competitive processes having comparable rates (a) butadienylcyclopropane rearrangement via a transoid transition state (111 113) and (b) enda,enda-1,5-hydrogen... 

It was shown that [1,5]-hydrogen shift occurs in this case about 30 times more quickly than that in the cycloheptatriene, while the butadienylcyclopropane rearrangement proceeds 3 x 10 9 slower than the Cope rearrangement of the isomeric 2,5-diene 11054. 

The thermolysis of the bicyclodiene 109 at 225 °C gives rise to equilibrium mixture of cyclooctatriene and its transformation products (see below)54. More recently the influence of a methoxy group on the thermal behavior of the bicyclo[5.1.0]octa-2,4-diene system was studied56. Heating of 8-ewdo-methoxydiene 115 in cyclooctane at 95 °C gaves rise to methoxy substituted diene 117 and not to the product 116 of butadienylcyclopropane rearrangement (equation 41). The thermolysis of the 8-exo-isomer 118 has taken place as an equilibrium reaction to give 6-ewdo-methoxy diene 119 (equation 42)56. These two reaction partners were separated by TLC. 

In bicyclo[5.1.0]octa-2,4-diene 109 which is quite stable at room temperature the so-called degenerate butadienylcyclopropane rearrangement takes place at elevated temperatures (above 110°C), and it can be revealed by using the deuterium labels (equation This transformation is interesting because the bicyclic diene 109 shows the... 

Three more reactions, which presumably proceed via carbopalladation steps without subsequent dehydropalladation, should be mentioned (Scheme 24). The first one is the diastereoselective formal [3 + 2] cycloaddition of the chiral nonracemic (/3-sulfinyl)vinylcyclopropane derivative 109 onto acrylonitrile (110). The second example is the Pd-catalyzed asymmetric vinylcyclopropane to cyclopentene rearrangement of the chiral nonracemic E)- and (Z)-arylsulflnyl-l,3-butadienylcyclopropane derivatives 112 [66] Plausible mechanisms that can rationalize the stereochemical outcome of the reactions were proposed in both publications. ... 

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