Even with mild acids, the aliphatic ketone Claisen rearrangements suffer from the lack of universal catalyst. Faulkner and Johnson concluded in 1973 that "there is no way to predict the best acid catalyst" for ketone Claisen reactions with unsaturated ketals. Baeckström and Li reported that the Claisen reactions with allylic alcohols and 2,2-dimethoxypropane required separate optimization for each substrate. We hypothesized that catalyst decay might lie behind these erratic results. Surprisingly, typical experimental optimization protocols in organic synthesis do not systematically address the issue of catalyst decomposition. Scheme 1. Acid catalyzed aliphatic ketone Claisen rearrangement.