D 2721 (OTTO) Dimethyl acetylenedicarboxylate, 99% Cas 762-42-5 - used in Pharmaceutical and electronic industry. D 2721 (OTTO) Dimethyl acetylenedicarboxylate, 99% Cas 762-42-5 - used in organic synthesis. It also acts as an intermediate in chemical research. It is also used in Diels-Alder Reaction.