We set out to test the hypothesis of ligand consumption by identifying the fate of the fumarate in the activation process. Specifically, we examined reactions with an elevated catalyst loading to allow the fate of the fumarate ligand to be tracked. Precatalyst 7 is readily prepared from Ni(COD)2, IMes, and di-(otolyl) fumarate, it possesses excellent stability and reactivity, and its structure (Figure ) is analogous to previously reported catalyst 2. In using 50 mol % loading of catalyst 7 in the three-component coupling of 4-fluorobenzaldehyde, 1-phenyl propyne, and triethylsilane, product 18 was isolated. 18 might result from a four-component reductive cycloaddition including the di-(o-tolyl) fumarate from the nickel catalyst, and byproduct 19 was observed by GCMS analysis (Scheme 1). The process resembles Et3B-mediated reductive cycloaddition involving enoates, alkynes, and aldehydes, 12 but has not been observed or proposed as a mechanism for catalyst activation. Given the complexity and uncertain mechanism of the formation of byproduct 18, we turned to computational reaction pathway evaluation tools to provide a clear explanation for these phenomena. To determine whether a given catalyst goes through activation path A or B, the highest energy transition states of both pathways need to be compared. In the case of catalyst 7, with an IMes ligand, the transition state for ketene elimination (IMes-TS-II-B, 22.0 kcal/mol) in path B is significantly higher in energy than the highest energy transition state in path A (IMes-TS-II-A, 15.1 kcal/mol), which suggests that catalyst 7 undergoes activation via path A.