Declaratory action for the non-existence of an arbitration clause. Party that recognizes as valid only the arbitration clause of a memorandum of understanding (MOU) entered into after the "contract for the purchase and sale of rights and obligations of PCH Verde 3". "Questions regarding the existence, validity and effectiveness of the arbitration clause that must first be resolved before the arbitral tribunal. Impossibility of using the judicial route to obstruct the installation of the arbitral tribunal and prevent its development." Supervening loss of appellate procedural interest in view of the arbitrator's independence statement having already been signed: