E1689 (OTTO) Ethyl 4-pyrazolecarboxylate, 98% Cas 37622-90-5 - used in the preparation of 4-chloromethylpyrazole. E1689 (OTTO) Ethyl 4-pyrazolecarboxylate, 98% Cas 37622-90-5 - used as starting material in a copper-diamine-catalyzed N-arylation reaction.