Most of the relevant literature describing the BA reaction did not show completion of the purification process all the way to the desired API, the BDQ (3) fumarate salt. In the cases where this data was displayed, BDQ (3) fumarate isolated yield was no more than 10 % (see Supporting Information, Table ). An additional drawback to this methodology that also contributes to lowering the yield of product is the low conversion of starting materials 1 and 2 (30 to 60 %). In theory, the unreacted starting materials can be recovered after the 1,2-addition, and a higher recovery percentage can be achieved by treating the undesired stereoisomers ent-3, 4, and ent-4 with base, which promotes the retro-addition towards 1 and 2. Nevertheless, there is no available literature showing how the recovered quinoline 1 and ketone 2 can be separated at scale without the use of chromatography. Thus, practical limitations prevent these low-yielding processes from being economical due to the considerable loss of material through the process. Given that the starting materials 1 and 2 are the primary cost-drivers in the BA reaction, the low BDQ (3) yield results in a significant waste of material driving up the total cost of the product. Thus, methods to improve this 1,2-addition step would significantly impact the API manufacturing cost.