Cope Rearrangement
Cope rearrangement involves the thermal isomerization of 1,5-dienes by [3,3] sigmatropic rearrangement. The reaction is reversible and produces an equillibrium mixture of the dienes. That isomer, however, predominates which is thermodynamically more stable. The reaction is facile (occuring at lower temperature) when there is a phenyl or carbethoxy group at 3- or 4-positions. This is due to conjugation of the groups with the double bonds in the product with consequent stablizatoin. When catalysed by transition metal compounds, Cope rearrangement of simple 1, 5-dienes can occur at room temperature.
