production of the ring-opening carbonyl-olefin metathesis (ROCOM) product 4 contaminated by various amounts of oligomeric products 5 (Table ). A brief survey of conditions revealed that both the structure of the hydrazine and the co-acid salt impacted the ratio of these two products. Pyrazolidine A was the least efficient and generated only the ROCOM adduct 4 in low yield (entry 1), while [2.2.1]-bicyclic hydrazine B led to an 8:1 mixture in favor of 4, regardless of the co-acid (entries 2 and 3). On the other hand, the [2.2.2]-bicyclic hydrazine C resulted in the largest proportions of the oligomeric product 5 (entries 4-6). The co-acid impacted this ratio, with the largest proportion of oligomer (~33%) formed with the bis-HBF4 salt of C. We presume that the amount of oligomer formation was inversely proportional to the propensity of the ring-opened hydrazonium intermediates (1 in Figure ) to undergo hydrolysis. [a] See ESI for experimental details. Yields reflect isolated and purified ROCOM product.