Process for the preparation of substituted norbornene derivatives

A process for preparing substituted norbornene derivatives of the formula ##STR6## wherein R and R' are independently alkyl or alkylene groups of 1 to 20 carbon atoms provided that the total number of carbon atoms for R and R' is not greater than 20, or R and R' together with the ring carbons to which they are bonded form one or more saturated or unsaturated rings of 6 to 16 carbon atoms, or one of R and R' is hydrogen, said process comprising reacting cyclopentadiene or dicyclopentadiene with an olefin or a cycloolefin at a temperature between 100.degree. and 300.degree. C., at a pressure sufficient to maintain the reaction in liquid phase which is between 50 and 2500 psi and in the presence of a chlorinated or a brominated hydrocarbon solvent.