Temperature and reaction conditions can dramatically affect the outcome of electrophilic reactions of dienes, especially in terms of kinetic versus thermodynamic control:
At low temperatures, the reaction is likely to be under kinetic control, favoring the formation of the product that forms at the fastest rate, which is typically the less stable, less substituted alkene (the kinetic product).
However, as the reaction temperature is increased, the system shifts towards thermodynamic control, where the more stable, more substituted alkene (the thermodynamic product) predominates because products can interconvert and the equilibrium favors the more stable product.