I reacently found this explanation for the reaction above mentioned reaction that I am investigating:
The maleic anhydride acts as a Lewis acid that interacts with the thermally activated Cl which gives origin to a carbo cation which eventually gives rise to a diene which is then subject to a Diels-alder condensation. Obviously there is no cyclization in this reaction but I would just like to find out what will be the major product. Keep in mind that the reaction is performed at 200 Celcius so the thermodynamic product will probably be favoured. Some insight would be greatly appreciated.